Add 'b_pie' compiler option

On Android executables must be position independent, many
distributions enable it by default too for security reasons.

7 files changed, 58 insertions, 8 deletions

diff --git a/docs/markdown/Builtin-options.md b/docs/markdown/Builtin-options.md
index 55d82a5..ce14304 100644
--- a/docs/markdown/Builtin-options.md
+++ b/docs/markdown/Builtin-options.md
@@ -82,6 +82,7 @@ platforms or with all compilers:
 | b_pgo       | off           | off, generate, use      | Use profile guided optimization |
 | b_sanitize  | none          | see below               | Code sanitizer to use |
 | b_staticpic | true          | true, false             | Build static libraries as position independent |
+| b_pie       | false         | true, false             | Build position-independent executables (since 0.49.0)|
 
 The value of `b_sanitize` can be one of: `none`, `address`, `thread`,
 `undefined`, `memory`, `address,undefined`.
diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index e4c9303..64ed9d1 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -552,6 +552,7 @@ be passed to [shared and static libraries](#library).
 - `d_unittest`, when set to true, the D modules are compiled in debug mode
 - `d_module_versions` list of module version identifiers set when compiling D sources
 - `d_debug` list of module debug identifiers set when compiling D sources
+- `pie` *(added 0.49.0)* build a position-independent executable
 
 The list of `sources`, `objects`, and `dependencies` is always
 flattened, which means you can freely nest and add lists while
diff --git a/docs/markdown/snippets/pie.md b/docs/markdown/snippets/pie.md
new file mode 100644
index 0000000..a9be174
--- /dev/null
+++ b/docs/markdown/snippets/pie.md
@@ -0,0 +1,6 @@
+## Position-independent executables
+
+When `b_pie` option, or `executable()`'s `pie` keyword argument is set to
+`true`, position-independent executables are built. All their objects are built
+with `-fPIE` and the executable is linked with `-pie`. Any static library they
+link must be built with `pic` set to `true` (see `b_staticpic` option).
diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 28ef670..f12b357 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -552,6 +552,8 @@ class Backend:
         # Set -fPIC for static libraries by default unless explicitly disabled
         if isinstance(target, build.StaticLibrary) and target.pic:
             commands += compiler.get_pic_args()
+        if isinstance(target, build.Executable) and target.pie:
+            commands += compiler.get_pie_args()
         # Add compile args needed to find external dependencies. Link args are
         # added while generating the link command.
         # NOTE: We must preserve the order in which external deps are
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index b564311..d8370c2 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -2245,6 +2245,8 @@ rule FORTRAN_DEP_HACK%s
             # If implib, and that's significant on this platform (i.e. Windows using either GCC or Visual Studio)
             if target.import_filename:
                 commands += linker.gen_import_library_args(os.path.join(self.get_target_dir(target), target.import_filename))
+            if target.pie:
+                commands += linker.get_pie_link_args()
         elif isinstance(target, build.SharedLibrary):
             if isinstance(target, build.SharedModule):
                 options = self.environment.coredata.base_options
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 8ba5465..f2a6d9c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -84,7 +84,7 @@ known_build_target_kwargs = (
     rust_kwargs |
     cs_kwargs)
 
-known_exe_kwargs = known_build_target_kwargs | {'implib', 'export_dynamic'}
+known_exe_kwargs = known_build_target_kwargs | {'implib', 'export_dynamic', 'pie'}
 known_shlib_kwargs = known_build_target_kwargs | {'version', 'soversion', 'vs_module_defs', 'darwin_versions'}
 known_shmod_kwargs = known_build_target_kwargs
 known_stlib_kwargs = known_build_target_kwargs | {'pic'}
@@ -414,6 +414,8 @@ class BuildTarget(Target):
         self.generated = []
         self.extra_files = []
         self.d_features = {}
+        self.pic = False
+        self.pie = False
         # Sources can be:
         # 1. Pre-existing source files in the source tree
         # 2. Pre-existing sources generated by configure_file in the build tree
@@ -869,13 +871,14 @@ This will become a hard error in a future Meson release.''')
             # since library loading is done differently)
             if for_darwin(self.is_cross, self.environment) or for_windows(self.is_cross, self.environment):
                 self.pic = True
-            elif '-fPIC' in clist + cpplist:
-                mlog.warning("Use the 'pic' kwarg instead of passing -fPIC manually to static library {!r}".format(self.name))
-                self.pic = True
             else:
-                self.pic = kwargs.get('pic', False)
-                if not isinstance(self.pic, bool):
-                    raise InvalidArguments('Argument pic to static library {!r} must be boolean'.format(self.name))
+                self.pic = self._extract_pic_pie(kwargs, 'pic')
+        if isinstance(self, Executable):
+            # Executables must be PIE on Android
+            if for_android(self.is_cross, self.environment):
+                self.pie = True
+            else:
+                self.pie = self._extract_pic_pie(kwargs, 'pie')
         self.implicit_include_directories = kwargs.get('implicit_include_directories', True)
         if not isinstance(self.implicit_include_directories, bool):
             raise InvalidArguments('Implicit_include_directories must be a boolean.')
@@ -888,6 +891,18 @@ This will become a hard error in a future Meson release.''')
                 raise InvalidArguments('GNU symbol visibility arg %s not one of: %s',
                                        self.symbol_visibility, ', '.join(permitted))
 
+    def _extract_pic_pie(self, kwargs, arg):
+        # Check if we have -fPIC, -fpic, -fPIE, or -fpie in cflags
+        all_flags = self.extra_args['c'] + self.extra_args['cpp']
+        if '-f' + arg.lower() in all_flags or '-f' + arg.upper() in all_flags:
+            mlog.warning("Use the '{}' kwarg instead of passing '{}' manually to {!r}".format(arg, '-f' + arg, self.name))
+            return True
+
+        val = kwargs.get(arg, False)
+        if not isinstance(val, bool):
+            raise InvalidArguments('Argument {} to {!r} must be boolean'.format(arg, self.name))
+        return val
+
     def get_filename(self):
         return self.filename
 
@@ -1307,6 +1322,8 @@ class Executable(BuildTarget):
     known_kwargs = known_exe_kwargs
 
     def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
+        if 'pie' not in kwargs and 'b_pie' in environment.coredata.base_options:
+            kwargs['pie'] = environment.coredata.base_options['b_pie'].value
         super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
         # Unless overridden, executables have no suffix or prefix. Except on
         # Windows and with C#/Mono executables where the suffix is 'exe'
diff --git a/mesonbuild/compilers/compilers.py b/mesonbuild/compilers/compilers.py
index 26eec48..50fda5a 100644
--- a/mesonbuild/compilers/compilers.py
+++ b/mesonbuild/compilers/compilers.py
@@ -331,6 +331,9 @@ base_options = {'b_pch': coredata.UserBooleanOption('b_pch', 'Use precompiled he
                 'b_staticpic': coredata.UserBooleanOption('b_staticpic',
                                                           'Build static libraries as position independent',
                                                           True),
+                'b_pie': coredata.UserBooleanOption('b_pie',
+                                                    'Build executables as position independent',
+                                                    False),
                 'b_bitcode': coredata.UserBooleanOption('b_bitcode',
                                                         'Generate and embed bitcode (only macOS and iOS)',
                                                         False),
@@ -1180,6 +1183,18 @@ class Compiler:
         raise EnvironmentException(
             'Language {} does not support function attributes.'.format(self.get_display_language()))
 
+    def get_pic_args(self):
+        m = 'Language {} does not support position-independent code'
+        raise EnvironmentException(m.format(self.get_display_language()))
+
+    def get_pie_args(self):
+        m = 'Language {} does not support position-independent executable'
+        raise EnvironmentException(m.format(self.get_display_language()))
+
+    def get_pie_link_args(self):
+        m = 'Language {} does not support position-independent executable'
+        raise EnvironmentException(m.format(self.get_display_language()))
+
 
 @enum.unique
 class CompilerType(enum.Enum):
@@ -1322,7 +1337,7 @@ class GnuLikeCompiler(abc.ABC):
     def __init__(self, compiler_type):
         self.compiler_type = compiler_type
         self.base_options = ['b_pch', 'b_lto', 'b_pgo', 'b_sanitize', 'b_coverage',
-                             'b_ndebug', 'b_staticpic']
+                             'b_ndebug', 'b_staticpic', 'b_pie']
         if not self.compiler_type.is_osx_compiler and not self.compiler_type.is_windows_compiler:
             self.base_options.append('b_lundef')
         if not self.compiler_type.is_windows_compiler:
@@ -1345,6 +1360,12 @@ class GnuLikeCompiler(abc.ABC):
             return [] # On Window and OS X, pic is always on.
         return ['-fPIC']
 
+    def get_pie_args(self):
+        return ['-fPIE']
+
+    def get_pie_link_args(self):
+        return ['-pie']
+
     def get_buildtype_args(self, buildtype):
         return gnulike_buildtype_args[buildtype]