Merge pull request #1321 from centricular/compiler-args-class

Improve compiler argument handling with a new class CompilerArgs derived from list()

21 files changed, 730 insertions, 271 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 6f8a50e..4988f28 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -21,6 +21,7 @@ from .. import compilers
 import json
 import subprocess
 from ..mesonlib import MesonException, get_compiler_for_source, classify_unity_sources
+from ..compilers import CompilerArgs
 
 class CleanTrees:
     '''
@@ -338,32 +339,59 @@ class Backend:
         return extra_args
 
     def generate_basic_compiler_args(self, target, compiler, no_warn_args=False):
-        commands = []
+        # Create an empty commands list, and start adding arguments from
+        # various sources in the order in which they must override each other
+        # starting from hard-coded defaults followed by build options and so on.
+        commands = CompilerArgs(compiler)
+        # First, the trivial ones that are impossible to override.
+        #
+        # Add -nostdinc/-nostdinc++ if needed; can't be overriden
         commands += self.get_cross_stdlib_args(target, compiler)
+        # Add things like /NOLOGO or -pipe; usually can't be overriden
         commands += compiler.get_always_args()
+        # Only add warning-flags by default if the buildtype enables it, and if
+        # we weren't explicitly asked to not emit warnings (for Vala, f.ex)
         if no_warn_args:
             commands += compiler.get_no_warn_args()
         elif self.environment.coredata.get_builtin_option('buildtype') != 'plain':
             commands += compiler.get_warn_args(self.environment.coredata.get_builtin_option('warning_level'))
+        # Add -Werror if werror=true is set in the build options set on the
+        # command-line or default_options inside project(). This only sets the
+        # action to be done for warnings if/when they are emitted, so it's ok
+        # to set it after get_no_warn_args() or get_warn_args().
+        if self.environment.coredata.get_builtin_option('werror'):
+            commands += compiler.get_werror_args()
+        # Add compile args for c_* or cpp_* build options set on the
+        # command-line or default_options inside project().
         commands += compiler.get_option_compile_args(self.environment.coredata.compiler_options)
-        commands += self.build.get_global_args(compiler)
+        # Add buildtype args: optimization level, debugging, etc.
+        commands += compiler.get_buildtype_args(self.environment.coredata.get_builtin_option('buildtype'))
+        # Add compile args added using add_project_arguments()
         commands += self.build.get_project_args(compiler, target.subproject)
+        # Add compile args added using add_global_arguments()
+        # These override per-project arguments
+        commands += self.build.get_global_args(compiler)
+        # Compile args added from the env: CFLAGS/CXXFLAGS, etc. We want these
+        # to override all the defaults, but not the per-target compile args.
         commands += self.environment.coredata.external_args[compiler.get_language()]
-        commands += self.escape_extra_args(compiler, target.get_extra_args(compiler.get_language()))
-        commands += compiler.get_buildtype_args(self.environment.coredata.get_builtin_option('buildtype'))
-        if self.environment.coredata.get_builtin_option('werror'):
-            commands += compiler.get_werror_args()
+        # Always set -fPIC for shared libraries
         if isinstance(target, build.SharedLibrary):
             commands += compiler.get_pic_args()
+        # Set -fPIC for static libraries by default unless explicitly disabled
         if isinstance(target, build.StaticLibrary) and target.pic:
             commands += compiler.get_pic_args()
+        # Add compile args needed to find external dependencies
+        # Link args are added while generating the link command
         for dep in target.get_external_deps():
-            # Cflags required by external deps might have UNIX-specific flags,
-            # so filter them out if needed
-            commands += compiler.unix_compile_flags_to_native(dep.get_compile_args())
+            commands += dep.get_compile_args()
+            # Qt needs -fPIC for executables
+            # XXX: We should move to -fPIC for all executables
             if isinstance(target, build.Executable):
-                commands += dep.get_exe_args()
-
+                commands += dep.get_exe_args(compiler)
+            # For 'automagic' deps: Boost and GTest. Also dependency('threads').
+            # pkg-config puts the thread flags itself via `Cflags:`
+            if dep.need_threads():
+                commands += compiler.thread_flags()
         # Fortran requires extra include directives.
         if compiler.language == 'fortran':
             for lt in target.link_targets:
@@ -664,23 +692,3 @@ class Backend:
         for s in self.build.postconf_scripts:
             cmd = s['exe'] + s['args']
             subprocess.check_call(cmd, env=child_env)
-
-    # Subprojects of subprojects may cause the same dep args to be used
-    # multiple times. Remove duplicates here. Note that we can't dedup
-    # libraries based on name alone, because "-lfoo -lbar -lfoo" is
-    # a completely valid (though pathological) sequence and removing the
-    # latter may fail. Usually only applies to static libs, though.
-    def dedup_arguments(self, commands):
-        includes = {}
-        final_commands = []
-        previous = '-fsuch_arguments=woof'
-        for c in commands:
-            if c.startswith(('-I', '-L', '/LIBPATH')):
-                if c in includes:
-                    continue
-                includes[c] = True
-            if previous == c:
-                continue
-            previous = c
-            final_commands.append(c)
-        return final_commands
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 628718f..9444087 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -19,6 +19,7 @@ from .. import build
 from .. import mlog
 from .. import dependencies
 from .. import compilers
+from ..compilers import CompilerArgs
 from ..mesonlib import File, MesonException, get_compiler_for_source, Popen_safe
 from .backends import CleanTrees, InstallData
 from ..build import InvalidArguments
@@ -1725,7 +1726,7 @@ rule FORTRAN_DEP_HACK
 
     def generate_llvm_ir_compile(self, target, outfile, src):
         compiler = get_compiler_for_source(target.compilers.values(), src)
-        commands = []
+        commands = CompilerArgs(compiler)
         # Compiler args for compiling this target
         commands += compilers.get_base_compile_args(self.environment.coredata.base_options,
                                                     compiler)
@@ -1748,11 +1749,40 @@ rule FORTRAN_DEP_HACK
         # Write the Ninja build command
         compiler_name = 'llvm_ir{}_COMPILER'.format('_CROSS' if target.is_cross else '')
         element = NinjaBuildElement(self.all_outputs, rel_obj, compiler_name, rel_src)
-        commands = self.dedup_arguments(commands)
+        # Convert from GCC-style link argument naming to the naming used by the
+        # current compiler.
+        commands = commands.to_native()
         element.add_item('ARGS', commands)
         element.write(outfile)
         return rel_obj
 
+    def get_source_dir_include_args(self, target, compiler):
+        curdir = target.get_subdir()
+        tmppath = os.path.normpath(os.path.join(self.build_to_src, curdir))
+        return compiler.get_include_args(tmppath, False)
+
+    def get_build_dir_include_args(self, target, compiler):
+        curdir = target.get_subdir()
+        if curdir == '':
+            curdir = '.'
+        return compiler.get_include_args(curdir, False)
+
+    def get_custom_target_dir_include_args(self, target, compiler):
+        custom_target_include_dirs = []
+        for i in target.get_generated_sources():
+            # Generator output goes into the target private dir which is
+            # already in the include paths list. Only custom targets have their
+            # own target build dir.
+            if not isinstance(i, build.CustomTarget):
+                continue
+            idir = self.get_target_dir(i)
+            if idir not in custom_target_include_dirs:
+                custom_target_include_dirs.append(idir)
+        incs = []
+        for i in custom_target_include_dirs:
+            incs += compiler.get_include_args(i, False)
+        return incs
+
     def generate_single_compile(self, target, outfile, src, is_generated=False, header_deps=[], order_deps=[]):
         """
         Compiles C/C++, ObjC/ObjC++, Fortran, and D sources
@@ -1763,30 +1793,40 @@ rule FORTRAN_DEP_HACK
             raise AssertionError('BUG: sources should not contain headers {!r}'.format(src.fname))
         extra_orderdeps = []
         compiler = get_compiler_for_source(target.compilers.values(), src)
-        commands = []
-        # The first thing is implicit include directories: source, build and private.
-        commands += compiler.get_include_args(self.get_target_private_dir(target), False)
-        # Compiler args for compiling this target
+
+        # Create an empty commands list, and start adding arguments from
+        # various sources in the order in which they must override each other
+        commands = CompilerArgs(compiler)
+        # Add compiler args for compiling this target derived from 'base' build
+        # options passed on the command-line, in default_options, etc.
+        # These have the lowest priority.
         commands += compilers.get_base_compile_args(self.environment.coredata.base_options,
                                                     compiler)
-        # Add the root source and build directories as include dirs
-        curdir = target.get_subdir()
-        tmppath = os.path.normpath(os.path.join(self.build_to_src, curdir))
-        src_inc = compiler.get_include_args(tmppath, False)
-        if curdir == '':
-            curdir = '.'
-        build_inc = compiler.get_include_args(curdir, False)
-        commands += build_inc + src_inc
-        # -I args work differently than other ones. In them the first found
-        # directory is used whereas for other flags (such as -ffoo -fno-foo) the
-        # latest one is used.  Therefore put the internal include directories
-        # here before generating the "basic compiler args" so they override args
-        # coming from e.g. pkg-config.
+        # The code generated by valac is usually crap and has tons of unused
+        # variables and such, so disable warnings for Vala C sources.
+        no_warn_args = (is_generated == 'vala')
+        # Add compiler args and include paths from several sources; defaults,
+        # build options, external dependencies, etc.
+        commands += self.generate_basic_compiler_args(target, compiler, no_warn_args)
+        # Add include dirs from the `include_directories:` kwarg on the target
+        # and from `include_directories:` of internal deps of the target.
+        #
+        # Target include dirs should override internal deps include dirs.
+        #
+        # Include dirs from internal deps should override include dirs from
+        # external deps.
         for i in target.get_include_dirs():
             basedir = i.get_curdir()
             for d in i.get_incdirs():
-                expdir = os.path.join(basedir, d)
+                # Avoid superfluous '/.' at the end of paths when d is '.'
+                if d not in ('', '.'):
+                    expdir = os.path.join(basedir, d)
+                else:
+                    expdir = basedir
                 srctreedir = os.path.join(self.build_to_src, expdir)
+                # Add source subdir first so that the build subdir overrides it
+                sargs = compiler.get_include_args(srctreedir, i.is_system)
+                commands += sargs
                 # There may be include dirs where a build directory has not been
                 # created for some source dir. For example if someone does this:
                 #
@@ -1797,20 +1837,32 @@ rule FORTRAN_DEP_HACK
                     bargs = compiler.get_include_args(expdir, i.is_system)
                 else:
                     bargs = []
-                sargs = compiler.get_include_args(srctreedir, i.is_system)
                 commands += bargs
-                commands += sargs
             for d in i.get_extra_build_dirs():
                 commands += compiler.get_include_args(d, i.is_system)
-        commands += self.generate_basic_compiler_args(target, compiler,
-                                                      # The code generated by valac is usually crap
-                                                      # and has tons of unused variables and such,
-                                                      # so disable warnings for Vala C sources.
-                                                      no_warn_args=(is_generated == 'vala'))
-        for d in target.external_deps:
-            if d.need_threads():
-                commands += compiler.thread_flags()
-                break
+        # Add per-target compile args, f.ex, `c_args : ['-DFOO']`. We set these
+        # near the end since these are supposed to override everything else.
+        commands += self.escape_extra_args(compiler,
+                                           target.get_extra_args(compiler.get_language()))
+        # Add source dir and build dir. Project-specific and target-specific
+        # include paths must override per-target compile args, include paths
+        # from external dependencies, internal dependencies, and from
+        # per-target `include_directories:`
+        #
+        # We prefer headers in the build dir and the custom target dir over the
+        # source dir since, for instance, the user might have an
+        # srcdir == builddir Autotools build in their source tree. Many
+        # projects that are moving to Meson have both Meson and Autotools in
+        # parallel as part of the transition.
+        commands += self.get_source_dir_include_args(target, compiler)
+        commands += self.get_custom_target_dir_include_args(target, compiler)
+        commands += self.get_build_dir_include_args(target, compiler)
+        # Finally add the private dir for the target to the include path. This
+        # must override everything else and must be the final path added.
+        commands += compiler.get_include_args(self.get_target_private_dir(target), False)
+
+        # FIXME: This file handling is atrocious and broken. We need to
+        # replace it with File objects used consistently everywhere.
         if isinstance(src, RawFilename):
             rel_src = src.fname
             if os.path.isabs(src.fname):
@@ -1835,7 +1887,13 @@ rule FORTRAN_DEP_HACK
         rel_obj = os.path.join(self.get_target_private_dir(target), obj_basename)
         rel_obj += '.' + self.environment.get_object_suffix()
         dep_file = compiler.depfile_for_object(rel_obj)
+
+        # Add MSVC debug file generation compile flags: /Fd /FS
+        commands += self.get_compile_debugfile_args(compiler, target, rel_obj)
+
+        # PCH handling
         if self.environment.coredata.base_options.get('b_pch', False):
+            commands += self.get_pch_include_args(compiler, target)
             pchlist = target.get_pch(compiler.language)
         else:
             pchlist = []
@@ -1848,19 +1906,7 @@ rule FORTRAN_DEP_HACK
             i = os.path.join(self.get_target_private_dir(target), compiler.get_pch_name(pchlist[0]))
             arr.append(i)
             pch_dep = arr
-        custom_target_include_dirs = []
-        for i in target.get_generated_sources():
-            if not isinstance(i, build.CustomTarget):
-                continue
-            idir = self.get_target_dir(i)
-            if idir not in custom_target_include_dirs:
-                custom_target_include_dirs.append(idir)
-        for i in custom_target_include_dirs:
-            commands += compiler.get_include_args(i, False)
-        if self.environment.coredata.base_options.get('b_pch', False):
-            commands += self.get_pch_include_args(compiler, target)
 
-        commands += self.get_compile_debugfile_args(compiler, target, rel_obj)
         crstr = ''
         if target.is_cross:
             crstr = '_CROSS'
@@ -1895,7 +1941,9 @@ rule FORTRAN_DEP_HACK
             element.add_orderdep(d)
         element.add_orderdep(pch_dep)
         element.add_orderdep(extra_orderdeps)
-        commands = self.dedup_arguments(commands)
+        # Convert from GCC-style link argument naming to the naming used by the
+        # current compiler.
+        commands = commands.to_native()
         for i in self.get_fortran_orderdeps(target, compiler):
             element.add_orderdep(i)
         element.add_item('DEPFILE', dep_file)
@@ -1995,47 +2043,23 @@ rule FORTRAN_DEP_HACK
             return []
         return linker.get_no_stdlib_link_args()
 
-    def generate_link(self, target, outfile, outname, obj_list, linker, extra_args=[]):
-        if isinstance(target, build.StaticLibrary):
-            linker_base = 'STATIC'
-        else:
-            linker_base = linker.get_language() # Fixme.
-        if isinstance(target, build.SharedLibrary):
-            self.generate_shsym(outfile, target)
-        crstr = ''
-        if target.is_cross:
-            crstr = '_CROSS'
-        linker_rule = linker_base + crstr + '_LINKER'
+    def get_target_type_link_args(self, target, linker):
         abspath = os.path.join(self.environment.get_build_dir(), target.subdir)
         commands = []
-        if not isinstance(target, build.StaticLibrary):
-            commands += self.build.get_project_link_args(linker, target.subproject)
-            commands += self.build.get_global_link_args(linker)
-        commands += self.get_cross_stdlib_link_args(target, linker)
-        commands += linker.get_linker_always_args()
-        if not isinstance(target, build.StaticLibrary):
-            commands += compilers.get_base_link_args(self.environment.coredata.base_options,
-                                                     linker,
-                                                     isinstance(target, build.SharedModule))
-        commands += linker.get_buildtype_linker_args(self.environment.coredata.get_builtin_option('buildtype'))
-        commands += linker.get_option_link_args(self.environment.coredata.compiler_options)
-        commands += self.get_link_debugfile_args(linker, target, outname)
-        if not(isinstance(target, build.StaticLibrary)):
-            commands += self.environment.coredata.external_link_args[linker.get_language()]
         if isinstance(target, build.Executable):
+            # Currently only used with the Swift compiler to add '-emit-executable'
             commands += linker.get_std_exe_link_args()
         elif isinstance(target, build.SharedLibrary):
             if isinstance(target, build.SharedModule):
                 commands += linker.get_std_shared_module_link_args()
             else:
                 commands += linker.get_std_shared_lib_link_args()
+            # All shared libraries are PIC
             commands += linker.get_pic_args()
-            if hasattr(target, 'soversion'):
-                soversion = target.soversion
-            else:
-                soversion = None
+            # Add -Wl,-soname arguments on Linux, -install_name on OS X
             commands += linker.get_soname_args(target.prefix, target.name, target.suffix,
-                                               abspath, soversion, isinstance(target, build.SharedModule))
+                                               abspath, target.soversion,
+                                               isinstance(target, build.SharedModule))
             # This is only visited when using the Visual Studio toolchain
             if target.vs_module_defs and hasattr(linker, 'gen_vs_module_defs_args'):
                 commands += linker.gen_vs_module_defs_args(target.vs_module_defs.rel_to_builddir(self.build_to_src))
@@ -2046,17 +2070,75 @@ rule FORTRAN_DEP_HACK
             commands += linker.get_std_link_args()
         else:
             raise RuntimeError('Unknown build target type.')
-        # Link arguments of static libraries are not put in the command line of
-        # the library. They are instead appended to the command line where
-        # the static library is used.
+        return commands
+
+    def generate_link(self, target, outfile, outname, obj_list, linker, extra_args=[]):
+        if isinstance(target, build.StaticLibrary):
+            linker_base = 'STATIC'
+        else:
+            linker_base = linker.get_language() # Fixme.
+        if isinstance(target, build.SharedLibrary):
+            self.generate_shsym(outfile, target)
+        crstr = ''
+        if target.is_cross:
+            crstr = '_CROSS'
+        linker_rule = linker_base + crstr + '_LINKER'
+
+        # Create an empty commands list, and start adding link arguments from
+        # various sources in the order in which they must override each other
+        # starting from hard-coded defaults followed by build options and so on.
+        #
+        # Once all the linker options have been passed, we will start passing
+        # libraries and library paths from internal and external sources.
+        commands = CompilerArgs(linker)
+        # First, the trivial ones that are impossible to override.
+        #
+        # Add linker args for linking this target derived from 'base' build
+        # options passed on the command-line, in default_options, etc.
+        # These have the lowest priority.
+        if not isinstance(target, build.StaticLibrary):
+            commands += compilers.get_base_link_args(self.environment.coredata.base_options,
+                                                     linker,
+                                                     isinstance(target, build.SharedModule))
+        # Add -nostdlib if needed; can't be overriden
+        commands += self.get_cross_stdlib_link_args(target, linker)
+        # Add things like /NOLOGO; usually can't be overriden
+        commands += linker.get_linker_always_args()
+        # Add buildtype linker args: optimization level, etc.
+        commands += linker.get_buildtype_linker_args(self.environment.coredata.get_builtin_option('buildtype'))
+        # Add /DEBUG and the pdb filename when using MSVC
+        commands += self.get_link_debugfile_args(linker, target, outname)
+        # Add link args specific to this BuildTarget type, such as soname args,
+        # PIC, import library generation, etc.
+        commands += self.get_target_type_link_args(target, linker)
+        if not isinstance(target, build.StaticLibrary):
+            # Add link args added using add_project_link_arguments()
+            commands += self.build.get_project_link_args(linker, target.subproject)
+            # Add link args added using add_global_link_arguments()
+            # These override per-project link arguments
+            commands += self.build.get_global_link_args(linker)
+            # Link args added from the env: LDFLAGS. We want these to
+            # override all the defaults but not the per-target link args.
+            commands += self.environment.coredata.external_link_args[linker.get_language()]
+
+        # Now we will add libraries and library paths from various sources
+
+        # Add link args to link to all internal libraries (link_with:) and
+        # internal dependencies needed by this target.
         if linker_base == 'STATIC':
+            # Link arguments of static libraries are not put in the command
+            # line of the library. They are instead appended to the command
+            # line where the static library is used.
             dependencies = []
         else:
             dependencies = target.get_dependencies()
         commands += self.build_target_link_arguments(linker, dependencies)
+        # For 'automagic' deps: Boost and GTest. Also dependency('threads').
+        # pkg-config puts the thread flags itself via `Cflags:`
         for d in target.external_deps:
             if d.need_threads():
                 commands += linker.thread_link_flags()
+        # Only non-static built targets need link args and link dependencies
         if not isinstance(target, build.StaticLibrary):
             commands += target.link_args
             # External deps must be last because target link libraries may depend on them.
@@ -2066,12 +2148,24 @@ rule FORTRAN_DEP_HACK
                 if isinstance(d, build.StaticLibrary):
                     for dep in d.get_external_deps():
                         commands += dep.get_link_args()
+        # Add link args for c_* or cpp_* build options. Currently this only
+        # adds c_winlibs and cpp_winlibs when building for Windows. This needs
+        # to be after all internal and external libraries so that unresolved
+        # symbols from those can be found here. This is needed when the
+        # *_winlibs that we want to link to are static mingw64 libraries.
+        commands += linker.get_option_link_args(self.environment.coredata.compiler_options)
+        # Set runtime-paths so we can run executables without needing to set
+        # LD_LIBRARY_PATH, etc in the environment. Doesn't work on Windows.
         commands += linker.build_rpath_args(self.environment.get_build_dir(),
-                                            self.determine_rpath_dirs(target), target.install_rpath)
+                                            self.determine_rpath_dirs(target),
+                                            target.install_rpath)
+        # Add libraries generated by custom targets
         custom_target_libraries = self.get_custom_target_provided_libraries(target)
         commands += extra_args
         commands += custom_target_libraries
-        commands = linker.unix_link_flags_to_native(self.dedup_arguments(commands))
+        # Convert from GCC-style link argument naming to the naming used by the
+        # current compiler.
+        commands = commands.to_native()
         dep_targets = [self.get_dependency_filename(t) for t in dependencies]
         dep_targets += [os.path.join(self.environment.source_dir,
                                      target.subdir, t) for t in target.link_depends]
diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index 61f755b..3b79a9c 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -23,6 +23,7 @@ from .. import dependencies
 from .. import mlog
 from .. import compilers
 from ..build import BuildTarget
+from ..compilers import CompilerArgs
 from ..mesonlib import MesonException, File
 from ..environment import Environment
 
@@ -426,24 +427,25 @@ class Vs2010Backend(backends.Backend):
         pch_out.text = '$(IntDir)$(TargetName)-%s.pch' % lang
 
     def add_additional_options(self, lang, parent_node, file_args):
-        if len(file_args[lang]) == 0:
-            # We only need per file options if they were not set per project.
-            return
-        args = file_args[lang] + ['%(AdditionalOptions)']
+        args = []
+        for arg in file_args[lang].to_native():
+            if arg == '%(AdditionalOptions)':
+                args.append(arg)
+            else:
+                args.append(self.escape_additional_option(arg))
         ET.SubElement(parent_node, "AdditionalOptions").text = ' '.join(args)
 
     def add_preprocessor_defines(self, lang, parent_node, file_defines):
-        if len(file_defines[lang]) == 0:
-            # We only need per file options if they were not set per project.
-            return
-        defines = file_defines[lang] + ['%(PreprocessorDefinitions)']
+        defines = []
+        for define in file_defines[lang]:
+            if define == '%(PreprocessorDefinitions)':
+                defines.append(define)
+            else:
+                defines.append(self.escape_preprocessor_define(define))
         ET.SubElement(parent_node, "PreprocessorDefinitions").text = ';'.join(defines)
 
     def add_include_dirs(self, lang, parent_node, file_inc_dirs):
-        if len(file_inc_dirs[lang]) == 0:
-            # We only need per file options if they were not set per project.
-            return
-        dirs = file_inc_dirs[lang] + ['%(AdditionalIncludeDirectories)']
+        dirs = file_inc_dirs[lang]
         ET.SubElement(parent_node, "AdditionalIncludeDirectories").text = ';'.join(dirs)
 
     @staticmethod
@@ -668,90 +670,132 @@ class Vs2010Backend(backends.Backend):
         # Arguments, include dirs, defines for all files in the current target
         target_args = []
         target_defines = []
-        target_inc_dirs = ['.', self.relpath(self.get_target_private_dir(target),
-                                             self.get_target_dir(target)),
-                           proj_to_src_dir] + generated_files_include_dirs
+        target_inc_dirs = []
         # Arguments, include dirs, defines passed to individual files in
         # a target; perhaps because the args are language-specific
-        file_args = dict((lang, []) for lang in target.compilers)
+        #
+        # file_args is also later split out into defines and include_dirs in
+        # case someone passed those in there
+        file_args = dict((lang, CompilerArgs(comp)) for lang, comp in target.compilers.items())
         file_defines = dict((lang, []) for lang in target.compilers)
         file_inc_dirs = dict((lang, []) for lang in target.compilers)
-        for l, args in self.environment.coredata.external_args.items():
+        # The order in which these compile args are added must match
+        # generate_single_compile() and generate_basic_compiler_args()
+        for l, comp in target.compilers.items():
+            if l in file_args:
+                file_args[l] += compilers.get_base_compile_args(self.environment.coredata.base_options, comp)
+                file_args[l] += comp.get_option_compile_args(self.environment.coredata.compiler_options)
+        # Add compile args added using add_project_arguments()
+        for l, args in self.build.projects_args.get(target.subproject, {}).items():
             if l in file_args:
                 file_args[l] += args
+        # Add compile args added using add_global_arguments()
+        # These override per-project arguments
         for l, args in self.build.global_args.items():
             if l in file_args:
                 file_args[l] += args
-        for l, args in self.build.projects_args.get(target.subproject, {}).items():
+        # Compile args added from the env: CFLAGS/CXXFLAGS, etc. We want these
+        # to override all the defaults, but not the per-target compile args.
+        for l, args in self.environment.coredata.external_args.items():
             if l in file_args:
                 file_args[l] += args
+        for args in file_args.values():
+            # This is where Visual Studio will insert target_args, target_defines,
+            # etc, which are added later from external deps (see below).
+            args += ['%(AdditionalOptions)', '%(PreprocessorDefinitions)', '%(AdditionalIncludeDirectories)']
+            # Add include dirs from the `include_directories:` kwarg on the target
+            # and from `include_directories:` of internal deps of the target.
+            #
+            # Target include dirs should override internal deps include dirs.
+            #
+            # Include dirs from internal deps should override include dirs from
+            # external deps.
+            # These are per-target, but we still add them as per-file because we
+            # need them to be looked in first.
+            for d in target.get_include_dirs():
+                for i in d.get_incdirs():
+                    curdir = os.path.join(d.get_curdir(), i)
+                    args.append('-I' + self.relpath(curdir, target.subdir)) # build dir
+                    args.append('-I' + os.path.join(proj_to_src_root, curdir)) # src dir
+                for i in d.get_extra_build_dirs():
+                    curdir = os.path.join(d.get_curdir(), i)
+                    args.append('-I' + self.relpath(curdir, target.subdir))  # build dir
+        # Add per-target compile args, f.ex, `c_args : ['/DFOO']`. We set these
+        # near the end since these are supposed to override everything else.
         for l, args in target.extra_args.items():
             if l in file_args:
-                file_args[l] += compiler.unix_compile_flags_to_native(args)
-        for l, comp in target.compilers.items():
-            if l in file_args:
-                file_args[l] += comp.get_option_compile_args(self.environment.coredata.compiler_options)
+                file_args[l] += args
+        # The highest priority includes. In order of directory search:
+        # target private dir, target build dir, generated sources include dirs,
+        # target source dir
+        for args in file_args.values():
+            t_inc_dirs = ['.', self.relpath(self.get_target_private_dir(target),
+                                            self.get_target_dir(target))]
+            t_inc_dirs += generated_files_include_dirs + [proj_to_src_dir]
+            args += ['-I' + arg for arg in t_inc_dirs]
+
+        # Split preprocessor defines and include directories out of the list of
+        # all extra arguments. The rest go into %(AdditionalOptions).
+        for l, args in file_args.items():
+            for arg in args[:]:
+                if arg.startswith(('-D', '/D')) or arg == '%(PreprocessorDefinitions)':
+                    file_args[l].remove(arg)
+                    # Don't escape the marker
+                    if arg == '%(PreprocessorDefinitions)':
+                        define = arg
+                    else:
+                        define = arg[2:]
+                    # De-dup
+                    if define in file_defines[l]:
+                        file_defines[l].remove(define)
+                    file_defines[l].append(define)
+                elif arg.startswith(('-I', '/I')) or arg == '%(AdditionalIncludeDirectories)':
+                    file_args[l].remove(arg)
+                    # Don't escape the marker
+                    if arg == '%(AdditionalIncludeDirectories)':
+                        inc_dir = arg
+                    else:
+                        inc_dir = arg[2:]
+                    # De-dup
+                    if inc_dir not in file_inc_dirs[l]:
+                        file_inc_dirs[l].append(inc_dir)
+
+        # Split compile args needed to find external dependencies
+        # Link args are added while generating the link command
         for d in target.get_external_deps():
             # Cflags required by external deps might have UNIX-specific flags,
             # so filter them out if needed
-            d_compile_args = compiler.unix_compile_flags_to_native(d.get_compile_args())
+            d_compile_args = compiler.unix_args_to_native(d.get_compile_args())
             for arg in d_compile_args:
                 if arg.startswith(('-D', '/D')):
                     define = arg[2:]
                     # De-dup
-                    if define not in target_defines:
-                        target_defines.append(define)
+                    if define in target_defines:
+                        target_defines.remove(define)
+                    target_defines.append(define)
                 elif arg.startswith(('-I', '/I')):
                     inc_dir = arg[2:]
                     # De-dup
                     if inc_dir not in target_inc_dirs:
                         target_inc_dirs.append(inc_dir)
                 else:
-                    # De-dup
-                    if arg not in target_args:
-                        target_args.append(arg)
-
-        # Split preprocessor defines and include directories out of the list of
-        # all extra arguments. The rest go into %(AdditionalOptions).
-        for l, args in file_args.items():
-            file_args[l] = []
-            for arg in args:
-                if arg.startswith(('-D', '/D')):
-                    define = self.escape_preprocessor_define(arg[2:])
-                    # De-dup
-                    if define not in file_defines[l]:
-                        file_defines[l].append(define)
-                elif arg.startswith(('-I', '/I')):
-                    inc_dir = arg[2:]
-                    # De-dup
-                    if inc_dir not in file_inc_dirs[l]:
-                        file_inc_dirs[l].append(inc_dir)
-                else:
-                    file_args[l].append(self.escape_additional_option(arg))
+                    target_args.append(arg)
 
         languages += gen_langs
         if len(target_args) > 0:
             target_args.append('%(AdditionalOptions)')
             ET.SubElement(clconf, "AdditionalOptions").text = ' '.join(target_args)
 
-        for d in target.include_dirs:
-            for i in d.incdirs:
-                curdir = os.path.join(d.curdir, i)
-                target_inc_dirs.append(self.relpath(curdir, target.subdir)) # build dir
-                target_inc_dirs.append(os.path.join(proj_to_src_root, curdir)) # src dir
-            for i in d.get_extra_build_dirs():
-                curdir = os.path.join(d.curdir, i)
-                target_inc_dirs.append(self.relpath(curdir, target.subdir))  # build dir
-
         target_inc_dirs.append('%(AdditionalIncludeDirectories)')
         ET.SubElement(clconf, 'AdditionalIncludeDirectories').text = ';'.join(target_inc_dirs)
         target_defines.append('%(PreprocessorDefinitions)')
         ET.SubElement(clconf, 'PreprocessorDefinitions').text = ';'.join(target_defines)
-        rebuild = ET.SubElement(clconf, 'MinimalRebuild')
-        rebuild.text = 'true'
-        funclink = ET.SubElement(clconf, 'FunctionLevelLinking')
-        funclink.text = 'true'
+        ET.SubElement(clconf, 'MinimalRebuild').text = 'true'
+        ET.SubElement(clconf, 'FunctionLevelLinking').text = 'true'
         pch_node = ET.SubElement(clconf, 'PrecompiledHeader')
+        if self.environment.coredata.get_builtin_option('werror'):
+            ET.SubElement(clconf, 'TreatWarningAsError').text = 'true'
+        # Note: SuppressStartupBanner is /NOLOGO and is 'true' by default
         pch_sources = {}
         for lang in ['c', 'cpp']:
             pch = target.get_pch(lang)
@@ -773,19 +817,27 @@ class Vs2010Backend(backends.Backend):
 
         resourcecompile = ET.SubElement(compiles, 'ResourceCompile')
         ET.SubElement(resourcecompile, 'PreprocessorDefinitions')
+
+        # Linker options
         link = ET.SubElement(compiles, 'Link')
-        # Put all language args here, too.
-        extra_link_args = compiler.get_option_link_args(self.environment.coredata.compiler_options)
+        extra_link_args = CompilerArgs(compiler)
         # FIXME: Can these buildtype linker args be added as tags in the
         # vcxproj file (similar to buildtype compiler args) instead of in
         # AdditionalOptions?
         extra_link_args += compiler.get_buildtype_linker_args(self.buildtype)
-        for l in self.environment.coredata.external_link_args.values():
-            extra_link_args += l
         if not isinstance(target, build.StaticLibrary):
-            extra_link_args += target.link_args
             if isinstance(target, build.SharedModule):
                 extra_link_args += compiler.get_std_shared_module_link_args()
+            # Add link args added using add_project_link_arguments()
+            extra_link_args += self.build.get_project_link_args(compiler, target.subproject)
+            # Add link args added using add_global_link_arguments()
+            # These override per-project link arguments
+            extra_link_args += self.build.get_global_link_args(compiler)
+            # Link args added from the env: LDFLAGS. We want these to
+            # override all the defaults but not the per-target link args.
+            extra_link_args += self.environment.coredata.external_link_args[compiler.get_language()]
+            # Only non-static built targets need link args and link dependencies
+            extra_link_args += target.link_args
             # External deps must be last because target link libraries may depend on them.
             for dep in target.get_external_deps():
                 extra_link_args += dep.get_link_args()
@@ -793,8 +845,13 @@ class Vs2010Backend(backends.Backend):
                 if isinstance(d, build.StaticLibrary):
                     for dep in d.get_external_deps():
                         extra_link_args += dep.get_link_args()
-        extra_link_args = compiler.unix_link_flags_to_native(extra_link_args)
-        (additional_libpaths, additional_links, extra_link_args) = self.split_link_args(extra_link_args)
+        # Add link args for c_* or cpp_* build options. Currently this only
+        # adds c_winlibs and cpp_winlibs when building for Windows. This needs
+        # to be after all internal and external libraries so that unresolved
+        # symbols from those can be found here. This is needed when the
+        # *_winlibs that we want to link to are static mingw64 libraries.
+        extra_link_args += compiler.get_option_link_args(self.environment.coredata.compiler_options)
+        (additional_libpaths, additional_links, extra_link_args) = self.split_link_args(extra_link_args.to_native())
         if len(extra_link_args) > 0:
             extra_link_args.append('%(AdditionalOptions)')
             ET.SubElement(link, "AdditionalOptions").text = ' '.join(extra_link_args)
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index a9f08c3..5466431 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -170,6 +170,10 @@ class IncludeDirs:
         else:
             self.extra_build_dirs = extra_build_dirs
 
+    def __repr__(self):
+        r = '<{} {}/{}>'
+        return r.format(self.__class__.__name__, self.curdir, self.incdirs)
+
     def get_curdir(self):
         return self.curdir
 
@@ -585,14 +589,16 @@ class BuildTarget(Target):
         for i in self.link_depends:
             if not isinstance(i, str):
                 raise InvalidArguments('Link_depends arguments must be strings.')
-        inclist = kwargs.get('include_directories', [])
-        if not isinstance(inclist, list):
-            inclist = [inclist]
-        self.add_include_dirs(inclist)
         deplist = kwargs.get('dependencies', [])
         if not isinstance(deplist, list):
             deplist = [deplist]
         self.add_deps(deplist)
+        # Target-specific include dirs must be added after include dirs from
+        # internal deps (added inside self.add_deps()) to override correctly.
+        inclist = kwargs.get('include_directories', [])
+        if not isinstance(inclist, list):
+            inclist = [inclist]
+        self.add_include_dirs(inclist)
         self.custom_install_dir = kwargs.get('install_dir', None)
         if self.custom_install_dir is not None:
             if not isinstance(self.custom_install_dir, str):
diff --git a/mesonbuild/compilers.py b/mesonbuild/compilers.py
index 0a88d6b..bb9b04a 100644
--- a/mesonbuild/compilers.py
+++ b/mesonbuild/compilers.py
@@ -323,6 +323,175 @@ class RunResult:
         self.stdout = stdout
         self.stderr = stderr
 
+class CompilerArgs(list):
+    '''
+    Class derived from list() that manages a list of compiler arguments. Should
+    be used while constructing compiler arguments from various sources. Can be
+    operated with ordinary lists, so this does not need to be used everywhere.
+
+    All arguments must be inserted and stored in GCC-style (-lfoo, -Idir, etc)
+    and can converted to the native type of each compiler by using the
+    .to_native() method to which you must pass an instance of the compiler or
+    the compiler class.
+
+    New arguments added to this class (either with .append(), .extend(), or +=)
+    are added in a way that ensures that they override previous arguments.
+    For example:
+
+    >>> a = ['-Lfoo', '-lbar']
+    >>> a += ['-Lpho', '-lbaz']
+    >>> print(a)
+    ['-Lpho', '-Lfoo', '-lbar', '-lbaz']
+
+    Arguments will also be de-duped if they can be de-duped safely.
+
+    Note that because of all this, this class is not commutative and does not
+    preserve the order of arguments if it is safe to not. For example:
+    >>> ['-Ifoo', '-Ibar'] + ['-Ifez', '-Ibaz', '-Werror']
+    ['-Ifez', '-Ibaz', '-Ifoo', '-Ibar', '-Werror']
+    >>> ['-Ifez', '-Ibaz', '-Werror'] + ['-Ifoo', '-Ibar']
+    ['-Ifoo', '-Ibar', '-Ifez', '-Ibaz', '-Werror']
+
+    '''
+    # NOTE: currently this class is only for C-like compilers, but it can be
+    # extended to other languages easily. Just move the following to the
+    # compiler class and initialize when self.compiler is set.
+
+    # Arg prefixes that override by prepending instead of appending
+    prepend_prefixes = ('-I', '-L')
+    # Arg prefixes and args that must be de-duped by returning 2
+    dedup2_prefixes = ('-I', '-L', '-D')
+    dedup2_args = ()
+    # Arg prefixes and args that must be de-duped by returning 1
+    dedup1_prefixes = ()
+    dedup1_args = ('-c', '-S', '-E', '-pipe')
+    compiler = None
+
+    def _check_args(self, args):
+        cargs = []
+        if len(args) > 2:
+            raise TypeError("CompilerArgs() only accepts at most 2 arguments: "
+                            "The compiler, and optionally an initial list")
+        elif len(args) == 0:
+            return cargs
+        elif len(args) == 1:
+            if isinstance(args[0], (Compiler, StaticLinker)):
+                self.compiler = args[0]
+            else:
+                raise TypeError("you must pass a Compiler instance as one of "
+                                "the arguments")
+        elif len(args) == 2:
+            if isinstance(args[0], (Compiler, StaticLinker)):
+                self.compiler = args[0]
+                cargs = args[1]
+            elif isinstance(args[1], (Compiler, StaticLinker)):
+                cargs = args[0]
+                self.compiler = args[1]
+            else:
+                raise TypeError("you must pass a Compiler instance as one of "
+                                "the two arguments")
+        else:
+            raise AssertionError('Not reached')
+        return cargs
+
+    def __init__(self, *args):
+        super().__init__(self._check_args(args))
+
+    @classmethod
+    def _can_dedup(cls, arg):
+        '''
+        Returns whether the argument can be safely de-duped. This is dependent
+        on two things:
+
+        a) Whether an argument can be 'overriden' by a later argument.  For
+           example, -DFOO defines FOO and -UFOO undefines FOO. In this case, we
+           can safely remove the previous occurance and add a new one. The same
+           is true for include paths and library paths with -I and -L. For
+           these we return `2`. See `dedup2_prefixes` and `dedup2_args`.
+        b) Arguments that once specifie cannot be undone, such as `-c` or
+           `-pipe`. New instances of these can be completely skipped. For these
+           we return `1`. See `dedup1_prefixes` and `dedup1_args`.
+        c) Whether it matters where or how many times on the command-line
+           a particular argument is present. This can matter for symbol
+           resolution in static or shared libraries, so we cannot de-dup or
+           reorder them. For these we return `0`. This is the default.
+        '''
+        if arg.startswith(cls.dedup2_prefixes) or arg in cls.dedup2_args:
+            return 2
+        if arg.startswith(cls.dedup1_prefixes) or arg in cls.dedup1_args:
+            return 1
+        return 0
+
+    @classmethod
+    def _should_prepend(cls, arg):
+        if arg.startswith(cls.prepend_prefixes):
+            return True
+        return False
+
+    def to_native(self):
+        return self.compiler.unix_args_to_native(self)
+
+    def __add__(self, args):
+        new = CompilerArgs(self, self.compiler)
+        new += args
+        return new
+
+    def __iadd__(self, args):
+        '''
+        Add two CompilerArgs while taking into account overriding of arguments
+        and while preserving the order of arguments as much as possible
+        '''
+        pre = []
+        post = []
+        if not isinstance(args, list):
+            raise TypeError('can only concatenate list (not "{}") to list'.format(args))
+        for arg in args:
+            # If the argument can be de-duped, do it either by removing the
+            # previous occurance of it and adding a new one, or not adding the
+            # new occurance.
+            dedup = self._can_dedup(arg)
+            if dedup == 1:
+                # Argument already exists and adding a new instance is useless
+                if arg in self or arg in pre or arg in post:
+                    continue
+            if dedup == 2:
+                # Remove all previous occurances of the arg and add it anew
+                if arg in self:
+                    self.remove(arg)
+                if arg in pre:
+                    pre.remove(arg)
+                if arg in post:
+                    post.remove(arg)
+            if self._should_prepend(arg):
+                pre.append(arg)
+            else:
+                post.append(arg)
+        # Insert at the beginning
+        self[:0] = pre
+        # Append to the end
+        super().__iadd__(post)
+        return self
+
+    def __radd__(self, args):
+        new = CompilerArgs(args, self.compiler)
+        new += self
+        return new
+
+    def __mul__(self, args):
+        raise TypeError("can't multiply compiler arguments")
+
+    def __imul__(self, args):
+        raise TypeError("can't multiply compiler arguments")
+
+    def __rmul__(self, args):
+        raise TypeError("can't multiply compiler arguments")
+
+    def append(self, arg):
+        self.__iadd__([arg])
+
+    def extend(self, args):
+        self.__iadd__(args)
+
 class Compiler:
     def __init__(self, exelist, version):
         if isinstance(exelist, str):
@@ -412,11 +581,8 @@ class Compiler:
     def has_function(self, *args, **kwargs):
         raise EnvironmentException('Language %s does not support function checks.' % self.language)
 
-    def unix_link_flags_to_native(self, args):
-        "Always returns a copy that can be independently mutated"
-        return args[:]
-
-    def unix_compile_flags_to_native(self, args):
+    @classmethod
+    def unix_args_to_native(cls, args):
         "Always returns a copy that can be independently mutated"
         return args[:]
 
@@ -435,7 +601,7 @@ class Compiler:
                 self.language))
 
     def get_cross_extra_flags(self, environment, *, compile, link):
-        extra_flags = []
+        extra_flags = CompilerArgs(self)
         if self.is_cross and environment:
             if 'properties' in environment.cross_info.config:
                 lang_args_key = self.language + '_args'
@@ -474,7 +640,7 @@ class Compiler:
                 output = self._get_compile_output(tmpdirname, mode)
 
                 # Construct the compiler command-line
-                commands = self.get_exelist()
+                commands = CompilerArgs(self)
                 commands.append(srcname)
                 commands += extra_args
                 commands += self.get_always_args()
@@ -485,6 +651,8 @@ class Compiler:
                     commands += self.get_preprocess_only_args()
                 else:
                     commands += self.get_output_args(output)
+                # Generate full command-line with the exelist
+                commands = self.get_exelist() + commands.to_native()
                 mlog.debug('Running compile:')
                 mlog.debug('Working directory: ', tmpdirname)
                 mlog.debug('Command line: ', ' '.join(commands), '\n')
@@ -663,7 +831,7 @@ class CCompiler(Compiler):
         mlog.debug('Sanity testing ' + self.language + ' compiler:', ' '.join(self.exelist))
         mlog.debug('Is cross compiler: %s.' % str(self.is_cross))
 
-        extra_flags = []
+        extra_flags = CompilerArgs(self)
         source_name = os.path.join(work_dir, sname)
         binname = sname.rsplit('.', 1)[0]
         if self.is_cross:
@@ -742,51 +910,29 @@ class CCompiler(Compiler):
         }}'''
         return self.compiles(t.format(**fargs), env, extra_args, dependencies)
 
-    @staticmethod
-    def _override_args(args, override):
-        '''
-        Add @override to @args in such a way that arguments are overriden
-        correctly.
-
-        We want the include directories to be added first (since they are
-        chosen left-to-right) and all other arguments later (since they
-        override previous arguments or add to a list that's chosen
-        right-to-left).
-        '''
-        before_args = []
-        after_args = []
-        for arg in override:
-            if arg.startswith(('-I', '/I')):
-                before_args.append(arg)
-            else:
-                after_args.append(arg)
-        return before_args + args + after_args
-
     def compiles(self, code, env, extra_args=None, dependencies=None, mode='compile'):
         if extra_args is None:
             extra_args = []
-        if isinstance(extra_args, str):
+        elif isinstance(extra_args, str):
             extra_args = [extra_args]
         if dependencies is None:
             dependencies = []
         elif not isinstance(dependencies, list):
             dependencies = [dependencies]
-        # Add compile flags needed by dependencies after converting to the
-        # native type of the selected compiler
-        cargs = [a for d in dependencies for a in d.get_compile_args()]
-        args = self.unix_link_flags_to_native(cargs)
+        # Add compile flags needed by dependencies
+        args = CompilerArgs(self)
+        for d in dependencies:
+            args += d.get_compile_args()
         # Read c_args/cpp_args/etc from the cross-info file (if needed)
         args += self.get_cross_extra_flags(env, compile=True, link=False)
         # Add CFLAGS/CXXFLAGS/OBJCFLAGS/OBJCXXFLAGS from the env
         # We assume that the user has ensured these are compiler-specific
         args += env.coredata.external_args[self.language]
-        # Append extra_args to the compiler check args such that it overrides
-        extra_args = self._override_args(self.get_compiler_check_args(), extra_args)
-        extra_args = self.unix_link_flags_to_native(extra_args)
-        # Append both to the compiler args such that they override them
-        args = self._override_args(args, extra_args)
+        args += self.get_compiler_check_args()
+        # extra_args must override all other arguments, so we add them last
+        args += extra_args
         # We only want to compile; not link
-        with self.compile(code, args, mode) as p:
+        with self.compile(code, args.to_native(), mode) as p:
             return p.returncode == 0
 
     def _links_wrapper(self, code, env, extra_args, dependencies):
@@ -799,11 +945,11 @@ class CCompiler(Compiler):
             dependencies = []
         elif not isinstance(dependencies, list):
             dependencies = [dependencies]
-        # Add compile and link flags needed by dependencies after converting to
-        # the native type of the selected compiler
-        cargs = [a for d in dependencies for a in d.get_compile_args()]
-        link_args = [a for d in dependencies for a in d.get_link_args()]
-        args = self.unix_link_flags_to_native(cargs + link_args)
+        # Add compile and link flags needed by dependencies
+        args = CompilerArgs(self)
+        for d in dependencies:
+            args += d.get_compile_args()
+            args += d.get_link_args()
         # Select a CRT if needed since we're linking
         args += self.get_linker_debug_crt_args()
         # Read c_args/c_link_args/cpp_args/cpp_link_args/etc from the
@@ -812,12 +958,11 @@ class CCompiler(Compiler):
         # Add LDFLAGS from the env. We assume that the user has ensured these
         # are compiler-specific
         args += env.coredata.external_link_args[self.language]
-        # Append extra_args to the compiler check args such that it overrides
-        extra_args = self._override_args(self.get_compiler_check_args(), extra_args)
-        extra_args = self.unix_link_flags_to_native(extra_args)
-        # Append both to the compiler args such that they override them
-        args = self._override_args(args, extra_args)
-        return self.compile(code, args)
+        # Add compiler check args such that they override
+        args += self.get_compiler_check_args()
+        # extra_args must override all other arguments, so we add them last
+        args += extra_args
+        return self.compile(code, args.to_native())
 
     def links(self, code, env, extra_args=None, dependencies=None):
         with self._links_wrapper(code, env, extra_args, dependencies) as p:
@@ -1179,6 +1324,9 @@ class CPPCompiler(CCompiler):
             self.language = 'cpp'
         CCompiler.__init__(self, exelist, version, is_cross, exe_wrap)
 
+    def get_no_stdinc_args(self):
+        return ['-nostdinc++']
+
     def sanity_check(self, work_dir, environment):
         code = 'class breakCCompiler;int main(int argc, char **argv) { return 0; }\n'
         return self.sanity_check_impl(work_dir, environment, 'sanitycheckcpp.cc', code)
@@ -1686,7 +1834,8 @@ class DCompiler(Compiler):
                 paths = paths + ':' + padding
         return ['-L-rpath={}'.format(paths)]
 
-    def translate_args_to_nongnu(self, args):
+    @classmethod
+    def translate_args_to_nongnu(cls, args):
         dcargs = []
         # Translate common arguments to flags the LDC/DMD compilers
         # can understand.
@@ -1802,11 +1951,9 @@ class LLVMDCompiler(DCompiler):
         # -L is for the compiler, telling it to pass the second -L to the linker.
         return ['-L-L' + dirname]
 
-    def unix_link_flags_to_native(self, args):
-        return self.translate_args_to_nongnu(args)
-
-    def unix_compile_flags_to_native(self, args):
-        return self.translate_args_to_nongnu(args)
+    @classmethod
+    def unix_args_to_native(cls, args):
+        return cls.translate_args_to_nongnu(args)
 
 class DmdDCompiler(DCompiler):
     def __init__(self, exelist, version, is_cross):
@@ -1854,11 +2001,9 @@ class DmdDCompiler(DCompiler):
     def get_std_shared_lib_link_args(self):
         return ['-shared', '-defaultlib=libphobos2.so']
 
-    def unix_link_flags_to_native(self, args):
-        return self.translate_args_to_nongnu(args)
-
-    def unix_compile_flags_to_native(self, args):
-        return self.translate_args_to_nongnu(args)
+    @classmethod
+    def unix_args_to_native(cls, args):
+        return cls.translate_args_to_nongnu(args)
 
 class VisualStudioCCompiler(CCompiler):
     std_warn_args = ['/W3']
@@ -1978,9 +2123,14 @@ class VisualStudioCCompiler(CCompiler):
     def get_option_link_args(self, options):
         return options['c_winlibs'].value[:]
 
-    def unix_link_flags_to_native(self, args):
+    @classmethod
+    def unix_args_to_native(cls, args):
         result = []
         for i in args:
+            # -mms-bitfields is specific to MinGW-GCC
+            # -pthread is only valid for GCC
+            if i in ('-mms-bitfields', '-pthread'):
+                continue
             if i.startswith('-L'):
                 i = '/LIBPATH:' + i[2:]
             # Translate GNU-style -lfoo library name to the import library
@@ -1998,16 +2148,6 @@ class VisualStudioCCompiler(CCompiler):
             result.append(i)
         return result
 
-    def unix_compile_flags_to_native(self, args):
-        result = []
-        for i in args:
-            # -mms-bitfields is specific to MinGW-GCC
-            # -pthread is only valid for GCC
-            if i in ('-mms-bitfields', '-pthread'):
-                continue
-            result.append(i)
-        return result
-
     def get_werror_args(self):
         return ['/WX']
 
@@ -2795,8 +2935,10 @@ class NAGFortranCompiler(FortranCompiler):
     def get_warn_args(self, level):
         return NAGFortranCompiler.std_warn_args
 
+class StaticLinker:
+    pass
 
-class VisualStudioLinker:
+class VisualStudioLinker(StaticLinker):
     always_args = ['/NOLOGO']
 
     def __init__(self, exelist):
@@ -2832,18 +2974,16 @@ class VisualStudioLinker:
     def get_option_link_args(self, options):
         return []
 
-    def unix_link_flags_to_native(self, args):
-        return args[:]
-
-    def unix_compile_flags_to_native(self, args):
-        return args[:]
+    @classmethod
+    def unix_args_to_native(cls, args):
+        return VisualStudioCCompiler.unix_args_to_native(args)
 
     def get_link_debugfile_args(self, targetfile):
         pdbarr = targetfile.split('.')[:-1]
         pdbarr += ['pdb']
         return ['/DEBUG', '/PDB:' + '.'.join(pdbarr)]
 
-class ArLinker:
+class ArLinker(StaticLinker):
 
     def __init__(self, exelist):
         self.exelist = exelist
@@ -2885,10 +3025,8 @@ class ArLinker:
     def get_option_link_args(self, options):
         return []
 
-    def unix_link_flags_to_native(self, args):
-        return args[:]
-
-    def unix_compile_flags_to_native(self, args):
+    @classmethod
+    def unix_args_to_native(cls, args):
         return args[:]
 
     def get_link_debugfile_args(self, targetfile):
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 60bb10b..1ec769a 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -117,7 +117,9 @@ class CoreData:
         self.user_options = {}
         self.compiler_options = {}
         self.base_options = {}
-        self.external_args = {} # These are set from "the outside" with e.g. mesonconf
+        # These two, external_*args, are set via env vars CFLAGS, LDFLAGS, etc
+        # but only when not cross-compiling.
+        self.external_args = {}
         self.external_link_args = {}
         if options.cross_file is not None:
             self.cross_file = os.path.join(os.getcwd(), options.cross_file)
diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index 6ae91d4..b01e0a8 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -59,7 +59,7 @@ class Dependency:
     def get_name(self):
         return self.name
 
-    def get_exe_args(self):
+    def get_exe_args(self, compiler):
         return []
 
     def need_threads(self):
@@ -1045,16 +1045,14 @@ class QtBaseDependency(Dependency):
     def found(self):
         return self.is_found
 
-    def get_exe_args(self):
+    def get_exe_args(self, compiler):
         # Originally this was -fPIE but nowadays the default
         # for upstream and distros seems to be -reduce-relocations
         # which requires -fPIC. This may cause a performance
         # penalty when using self-built Qt or on platforms
         # where -fPIC is not required. If this is an issue
         # for you, patches are welcome.
-        if mesonlib.is_linux():
-            return ['-fPIC']
-        return []
+        return compiler.get_pic_args()
 
 class Qt5Dependency(QtBaseDependency):
     def __init__(self, env, kwargs):
diff --git a/run_unittests.py b/run_unittests.py
index 5eba222..b6ea073 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -14,11 +14,13 @@
 # limitations under the License.
 
 import stat
+import shlex
 import unittest, os, sys, shutil, time
 import subprocess
 import re, json
 import tempfile
 from glob import glob
+import mesonbuild.compilers
 import mesonbuild.environment
 import mesonbuild.mesonlib
 from mesonbuild.environment import detect_ninja, Environment
@@ -95,6 +97,62 @@ class InternalTests(unittest.TestCase):
                          stat.S_IRWXU | stat.S_ISUID |
                          stat.S_IRGRP | stat.S_IXGRP)
 
+    def test_compiler_args_class(self):
+        cargsfunc = mesonbuild.compilers.CompilerArgs
+        c = mesonbuild.environment.CCompiler([], 'fake', False)
+        # Test that bad initialization fails
+        self.assertRaises(TypeError, cargsfunc, [])
+        self.assertRaises(TypeError, cargsfunc, [], [])
+        self.assertRaises(TypeError, cargsfunc, c, [], [])
+        # Test that empty initialization works
+        a = cargsfunc(c)
+        self.assertEqual(a, [])
+        # Test that list initialization works
+        a = cargsfunc(['-I.', '-I..'], c)
+        self.assertEqual(a, ['-I.', '-I..'])
+        # Test that there is no de-dup on initialization
+        self.assertEqual(cargsfunc(['-I.', '-I.'], c), ['-I.', '-I.'])
+
+        ## Test that appending works
+        a.append('-I..')
+        self.assertEqual(a, ['-I..', '-I.'])
+        a.append('-O3')
+        self.assertEqual(a, ['-I..', '-I.', '-O3'])
+
+        ## Test that in-place addition works
+        a += ['-O2', '-O2']
+        self.assertEqual(a, ['-I..', '-I.', '-O3', '-O2', '-O2'])
+        # Test that removal works
+        a.remove('-O2')
+        self.assertEqual(a, ['-I..', '-I.', '-O3', '-O2'])
+        # Test that de-dup happens on addition
+        a += ['-Ifoo', '-Ifoo']
+        self.assertEqual(a, ['-Ifoo', '-I..', '-I.', '-O3', '-O2'])
+
+        # .extend() is just +=, so we don't test it
+
+        ## Test that addition works
+        # Test that adding a list with just one old arg works and yields the same array
+        a = a + ['-Ifoo']
+        self.assertEqual(a, ['-Ifoo', '-I..', '-I.', '-O3', '-O2'])
+        # Test that adding a list with one arg new and one old works
+        a = a + ['-Ifoo', '-Ibaz']
+        self.assertEqual(a, ['-Ifoo', '-Ibaz', '-I..', '-I.', '-O3', '-O2'])
+        # Test that adding args that must be prepended and appended works
+        a = a + ['-Ibar', '-Wall']
+        self.assertEqual(a, ['-Ibar', '-Ifoo', '-Ibaz', '-I..', '-I.', '-O3', '-O2', '-Wall'])
+
+        ## Test that reflected addition works
+        # Test that adding to a list with just one old arg works and DOES NOT yield the same array
+        a = ['-Ifoo'] + a
+        self.assertEqual(a, ['-Ibar', '-Ifoo', '-Ibaz', '-I..', '-I.', '-O3', '-O2', '-Wall'])
+        # Test that adding to a list with just one new arg that is not pre-pended works
+        a = ['-Werror'] + a
+        self.assertEqual(a, ['-Ibar', '-Ifoo', '-Ibaz', '-I..', '-I.', '-Werror', '-O3', '-O2', '-Wall'])
+        # Test that adding to a list with two new args preserves the order
+        a = ['-Ldir', '-Lbah'] + a
+        self.assertEqual(a, ['-Ibar', '-Ifoo', '-Ibaz', '-I..', '-I.', '-Ldir', '-Lbah', '-Werror', '-O3', '-O2', '-Wall'])
+
 
 class LinuxlikeTests(unittest.TestCase):
     def setUp(self):
@@ -416,7 +474,7 @@ class LinuxlikeTests(unittest.TestCase):
                 cmd = cmd[1:]
             # Verify that -I flags from the `args` kwarg are first
             # This is set in the '43 has function' test case
-            self.assertEqual(cmd[2], '-I/tmp')
+            self.assertEqual(cmd[1], '-I/tmp')
             # Verify that -O3 set via the environment is overriden by -O0
             Oargs = [arg for arg in cmd if arg.startswith('-O')]
             self.assertEqual(Oargs, [Oflag, '-O0'])
@@ -641,6 +699,38 @@ class LinuxlikeTests(unittest.TestCase):
             # The chown failed nonfatally if we're not root
             self.assertEqual(0, statf.st_uid)
 
+    def test_internal_include_order(self):
+        testdir = os.path.join(self.common_test_dir, '138 include order')
+        self.init(testdir)
+        for cmd in self.get_compdb():
+            if cmd['file'].endswith('/main.c'):
+                cmd = cmd['command']
+                break
+        else:
+            raise Exception('Could not find main.c command')
+        incs = [a for a in shlex.split(cmd) if a.startswith("-I")]
+        self.assertEqual(len(incs), 8)
+        # target private dir
+        self.assertEqual(incs[0], "-Isub4/someexe@exe")
+        # target build subdir
+        self.assertEqual(incs[1], "-Isub4")
+        # target source subdir
+        msg = "{!r} does not end with '/sub4'".format(incs[2])
+        self.assertTrue(incs[2].endswith("/sub4"), msg)
+        # include paths added via per-target c_args: ['-I'...]
+        msg = "{!r} does not end with '/sub3'".format(incs[3])
+        self.assertTrue(incs[3].endswith("/sub3"), msg)
+        # target include_directories: build dir
+        self.assertEqual(incs[4], "-Isub2")
+        # target include_directories: source dir
+        msg = "{!r} does not end with '/sub2'".format(incs[5])
+        self.assertTrue(incs[5].endswith("/sub2"), msg)
+        # target internal dependency include_directories: build dir
+        self.assertEqual(incs[6], "-Isub1")
+        # target internal dependency include_directories: source dir
+        msg = "{!r} does not end with '/sub1'".format(incs[7])
+        self.assertTrue(incs[7].endswith("/sub1"), msg)
+
 
 class RewriterTests(unittest.TestCase):
 
diff --git a/setup.cfg b/setup.cfg
index 9374560..b3adc59 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -13,5 +13,9 @@ ignore =
     # E305: expected 2 blank lines after class or function definition, found 1
     E305,
     # E401: multiple imports on one line
-    E401
+    E401,
+    # too many leading '#' for block comment
+    E266,
+    # module level import not at top of file
+    E402
 max-line-length = 120
diff --git a/test cases/common/138 include order/meson.build b/test cases/common/138 include order/meson.build
new file mode 100644
index 0000000..f744ae7
--- /dev/null
+++ b/test cases/common/138 include order/meson.build
@@ -0,0 +1,22 @@
+project('include order', 'c')
+
+# Test that the order of priority of include paths (from first to last) is:
+#
+# 1. Target's current build directory
+# 2. Target's current source directory
+# 3. Include paths added with the `c_args:` kwarg
+# 4. Include paths added with the `include_directories`: kwarg
+#    Within this, the build dir takes precedence over the source dir
+# 5. Include paths added via `include_directories:` of internal deps
+#    Within this, the build dir takes precedence over the source dir
+
+# Defines an internal dep
+subdir('sub1')
+# Defines a per-target include path
+subdir('sub2')
+# Directory for `c_args:` include path
+subdir('sub3')
+# The directory where the target resides
+subdir('sub4')
+
+test('eh', e)
diff --git a/test cases/common/138 include order/sub1/main.h b/test cases/common/138 include order/sub1/main.h
new file mode 100644
index 0000000..acf4a35
--- /dev/null
+++ b/test cases/common/138 include order/sub1/main.h
@@ -0,0 +1 @@
+#error "sub1/main.h included"
diff --git a/test cases/common/138 include order/sub1/meson.build b/test cases/common/138 include order/sub1/meson.build
new file mode 100644
index 0000000..9672945
--- /dev/null
+++ b/test cases/common/138 include order/sub1/meson.build
@@ -0,0 +1,4 @@
+i = include_directories('.')
+l = shared_library('somelib', 'some.c')
+dep = declare_dependency(link_with : l,
+                         include_directories : i)
diff --git a/test cases/common/138 include order/sub1/some.c b/test cases/common/138 include order/sub1/some.c
new file mode 100644
index 0000000..1ab0db4
--- /dev/null
+++ b/test cases/common/138 include order/sub1/some.c
@@ -0,0 +1,6 @@
+#if defined _WIN32 || defined __CYGWIN__
+  __declspec(dllexport)
+#endif
+int somefunc(void) {
+  return 1984;
+}
diff --git a/test cases/common/138 include order/sub1/some.h b/test cases/common/138 include order/sub1/some.h
new file mode 100644
index 0000000..6479492
--- /dev/null
+++ b/test cases/common/138 include order/sub1/some.h
@@ -0,0 +1,10 @@
+#pragma once
+
+#if defined _WIN32 || defined __CYGWIN__
+  #define DLL_PUBLIC __declspec(dllimport)
+#else
+  #define DLL_PUBLIC
+#endif
+
+DLL_PUBLIC
+int somefunc(void);
diff --git a/test cases/common/138 include order/sub2/main.h b/test cases/common/138 include order/sub2/main.h
new file mode 100644
index 0000000..b9c0da9
--- /dev/null
+++ b/test cases/common/138 include order/sub2/main.h
@@ -0,0 +1 @@
+#error "sub2/main.h included"
diff --git a/test cases/common/138 include order/sub2/meson.build b/test cases/common/138 include order/sub2/meson.build
new file mode 100644
index 0000000..7b49d6a
--- /dev/null
+++ b/test cases/common/138 include order/sub2/meson.build
@@ -0,0 +1 @@
+j = include_directories('.')
diff --git a/test cases/common/138 include order/sub3/main.h b/test cases/common/138 include order/sub3/main.h
new file mode 100644
index 0000000..1ab7231
--- /dev/null
+++ b/test cases/common/138 include order/sub3/main.h
@@ -0,0 +1 @@
+#error "sub3/main.h included"
diff --git a/test cases/common/138 include order/sub3/meson.build b/test cases/common/138 include order/sub3/meson.build
new file mode 100644
index 0000000..0bd3906
--- /dev/null
+++ b/test cases/common/138 include order/sub3/meson.build
@@ -0,0 +1 @@
+sub3 = meson.current_source_dir()
diff --git a/test cases/common/138 include order/sub4/main.c b/test cases/common/138 include order/sub4/main.c
new file mode 100644
index 0000000..0b25eed
--- /dev/null
+++ b/test cases/common/138 include order/sub4/main.c
@@ -0,0 +1,8 @@
+/* Use the <> include notation to force searching in include directories */
+#include <main.h>
+
+int main(int argc, char *argv[]) {
+  if (somefunc() == 1984)
+    return 0;
+  return 1;
+}
diff --git a/test cases/common/138 include order/sub4/main.h b/test cases/common/138 include order/sub4/main.h
new file mode 100644
index 0000000..194d7fe
--- /dev/null
+++ b/test cases/common/138 include order/sub4/main.h
@@ -0,0 +1,3 @@
+#pragma once
+
+#include "some.h"
diff --git a/test cases/common/138 include order/sub4/meson.build b/test cases/common/138 include order/sub4/meson.build
new file mode 100644
index 0000000..538899a
--- /dev/null
+++ b/test cases/common/138 include order/sub4/meson.build
@@ -0,0 +1,4 @@
+e = executable('someexe', 'main.c',
+               c_args : ['-I' + sub3],
+               include_directories : j,
+               dependencies : dep)