backends: Add custom target inc dirs before target inc dirs

Custom target include dirs must be overridable by target-specific
include dirs otherwise in case of header name collisions, the user has
no way to override this behaviour.

2 files changed, 15 insertions, 9 deletions

diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index dce3b80..bff173a 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -2038,6 +2038,12 @@ rule FORTRAN_DEP_HACK
         # 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 custom target dirs as includes automatically, but before
+        # target-specific include directories.
+        # XXX: Not sure if anyone actually uses this? It can cause problems in
+        # situations which increase the likelihood for a header name collision,
+        # such as in subprojects.
+        commands += self.get_custom_target_dir_include_args(target, compiler)
         # Add include dirs from the `include_directories:` kwarg on the target
         # and from `include_directories:` of internal deps of the target.
         #
@@ -2081,14 +2087,12 @@ rule FORTRAN_DEP_HACK
         # 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.
+        # We prefer headers in the build 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.
         if target.implicit_include_directories:
             commands += self.get_source_dir_include_args(target, compiler)
-        commands += self.get_custom_target_dir_include_args(target, compiler)
         if target.implicit_include_directories:
             commands += self.get_build_dir_include_args(target, compiler)
         # Finally add the private dir for the target to the include path. This
diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index 00ee34a..ec5ad7d 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -763,6 +763,10 @@ class Vs2010Backend(backends.Backend):
             # 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 custom target dirs as includes automatically, but before
+            # target-specific include dirs. See _generate_single_compile() in
+            # the ninja backend for caveats.
+            args += ['-I' + arg for arg in generated_files_include_dirs]
             # Add include dirs from the `include_directories:` kwarg on the target
             # and from `include_directories:` of internal deps of the target.
             #
@@ -789,14 +793,12 @@ class Vs2010Backend(backends.Backend):
             if l in file_args:
                 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
+        # target private dir, target build dir, 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))]
             if target.implicit_include_directories:
                 t_inc_dirs += ['.']
-            t_inc_dirs += generated_files_include_dirs
             if target.implicit_include_directories:
                 t_inc_dirs += [proj_to_src_dir]
             args += ['-I' + arg for arg in t_inc_dirs]