7 files changed, 20 insertions, 9 deletions
diff --git a/docs/markdown/snippets/per_subproject_builtin.md b/docs/markdown/snippets/per_subproject_builtin.md
index 44ed1c8..b0c3ce9 100644
--- a/docs/markdown/snippets/per_subproject_builtin.md
+++ b/docs/markdown/snippets/per_subproject_builtin.md
@@ -1,8 +1,9 @@
-## Per subproject `default_library` option
+## Per subproject `default_library` and `werror` options
 
-The `default_library` built-in option can now be defined per subproject. This is
-useful for example when building shared libraries in the main project, but static
-link a subproject.
+The `default_library` and `werror` built-in options can now be defined per subproject.
+This is useful for example when building shared libraries in the main project,
+but static link a subproject, or when the main project must build with no warnings
+but some subprojects cannot.
 
 Most of the time this would be used either by the parent project by setting
 subproject's default_options (e.g. `subproject('foo', default_options: 'default_library=static')`),
diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index ab922ba..687b122 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -179,7 +179,7 @@ class Backend:
         if option_name in target.option_overrides:
             override = target.option_overrides[option_name]
             return self.environment.coredata.validate_option_value(option_name, override)
-        return self.environment.coredata.get_builtin_option(option_name)
+        return self.environment.coredata.get_builtin_option(option_name, target.subproject)
 
     def get_target_filename_for_linking(self, target):
         # On some platforms (msvc for instance), the file that is used for
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 7038bf7..074f9e6 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -1104,7 +1104,7 @@ builtin_options = OrderedDict([
     ('unity',           BuiltinOption(UserComboOption, 'Unity build', 'off', choices=['on', 'off', 'subprojects'])),
     ('unity_size',      BuiltinOption(UserIntegerOption, 'Unity block size', (2, None, 4))),
     ('warning_level',   BuiltinOption(UserComboOption, 'Compiler warning level to use', '1', choices=['0', '1', '2', '3'])),
-    ('werror',          BuiltinOption(UserBooleanOption, 'Treat warnings as errors', False)),
+    ('werror',          BuiltinOption(UserBooleanOption, 'Treat warnings as errors', False, yielding=False)),
     ('wrap_mode',       BuiltinOption(UserComboOption, 'Wrap mode', 'default', choices=['default', 'nofallback', 'nodownload', 'forcefallback'])),
 ])
 
diff --git a/mesonbuild/modules/hotdoc.py b/mesonbuild/modules/hotdoc.py
index bf4386f..5c04e27 100644
--- a/mesonbuild/modules/hotdoc.py
+++ b/mesonbuild/modules/hotdoc.py
@@ -326,7 +326,7 @@ class HotdocTargetBuilder:
         for path in self.include_paths.keys():
             self.cmd.extend(['--include-path', path])
 
-        if self.state.environment.coredata.get_builtin_option('werror'):
+        if self.state.environment.coredata.get_builtin_option('werror', self.state.subproject):
             self.cmd.append('--fatal-warning')
         self.generate_hotdoc_config()
 
diff --git a/test cases/common/229 persubproject options/meson.build b/test cases/common/229 persubproject options/meson.build
index 6a76697..20dff90 100644
--- a/test cases/common/229 persubproject options/meson.build
+++ b/test cases/common/229 persubproject options/meson.build
@@ -1,6 +1,9 @@
-project('persubproject options', 'c', default_options : ['default_library=both'])
+project('persubproject options', 'c',
+  default_options : ['default_library=both',
+                     'werror=true'])
 
 assert(get_option('default_library') == 'both', 'Parent default_library should be "both"')
+assert(get_option('werror'))
 
 # Check it build both by calling a method only both_libraries target implement
 lib = library('lib1', 'foo.c')
diff --git a/test cases/common/229 persubproject options/subprojects/sub2/foo.c b/test cases/common/229 persubproject options/subprojects/sub2/foo.c
index 63e4de6..cf7201b 100644
--- a/test cases/common/229 persubproject options/subprojects/sub2/foo.c
+++ b/test cases/common/229 persubproject options/subprojects/sub2/foo.c
@@ -1,5 +1,9 @@
 int foo(void);
 
+#ifdef __GNUC__
+#warning This should not produce error
+#endif
+
 int foo(void) {
   return 0;
 }
diff --git a/test cases/common/229 persubproject options/subprojects/sub2/meson.build b/test cases/common/229 persubproject options/subprojects/sub2/meson.build
index 546884d..f1226b8 100644
--- a/test cases/common/229 persubproject options/subprojects/sub2/meson.build
+++ b/test cases/common/229 persubproject options/subprojects/sub2/meson.build
@@ -1,6 +1,9 @@
-project('sub2', 'c', default_options : ['default_library=shared'])
+project('sub2', 'c',
+ default_options : ['default_library=shared',
+                    'werror=false'])
 
 assert(get_option('default_library') == 'static', 'Parent should override default_library')
+assert(not get_option('werror'))
 
 # If it doesn't build only a static library, it would make target name clash.
 library('lib1', 'foo.c')