Add no-warning args while building Vala C code

This is done by adding a new compiler method called 'no_warn_args' which
returns the argument(s) required for the compiler to emit no warnings
for that compilation.

This take care of not disabling warnings for C code compiled into the
BuildTarget. Also includes tests for ensuring all this.

https://github.com/mesonbuild/meson/issues/864

mesonbuild/backend/backends.py

@@ -327,11 +327,14 @@ class Backend():
                 extra_args.append(arg)
         return extra_args
 
-    def generate_basic_compiler_args(self, target, compiler):
+    def generate_basic_compiler_args(self, target, compiler, no_warn_args=False):
         commands = []
         commands += self.get_cross_stdlib_args(target, compiler)
         commands += compiler.get_always_args()
-        commands += compiler.get_warn_args(self.environment.coredata.get_builtin_option('warning_level'))
+        if no_warn_args:
+            commands += compiler.get_no_warn_args()
+        else:
+            commands += compiler.get_warn_args(self.environment.coredata.get_builtin_option('warning_level'))
         commands += compiler.get_option_compile_args(self.environment.coredata.compiler_options)
         commands += self.build.get_global_args(compiler)
         commands += self.environment.coredata.external_args[compiler.get_language()]

mesonbuild/backend/ninjabackend.py

@@ -233,7 +233,7 @@ int dummy;
         if isinstance(target, build.RunTarget):
             self.generate_run_target(target, outfile)
         name = target.get_id()
-        gen_src_deps = []
+        vala_gen_sources = []
         if name in self.processed_targets:
             return
         if isinstance(target, build.Jar):
@@ -249,8 +249,7 @@ int dummy;
             self.generate_swift_target(target, outfile)
             return
         if 'vala' in target.compilers:
-            vala_output_files = self.generate_vala_compile(target, outfile)
+            vala_gen_sources = self.generate_vala_compile(target, outfile)
-            gen_src_deps += vala_output_files
         self.scan_fortran_module_outputs(target)
         self.process_target_dependencies(target, outfile)
         self.generate_custom_generator_rules(target, outfile)
@@ -318,9 +317,10 @@ int dummy;
             src_list.append(src)
             obj_list.append(self.generate_single_compile(target, outfile, src, True,
                                                          header_deps=header_deps))
-        # Generate compilation targets for sources belonging to this target that
+        # Generate compilation targets for C sources generated from Vala
-        # are generated by other rules (this is only used for Vala right now)
+        # sources. This can be extended to other $LANG->C compilers later if
-        for src in gen_src_deps:
+        # necessary.
+        for src in vala_gen_sources:
             src_list.append(src)
             if is_unity:
                 unity_src.append(os.path.join(self.environment.get_build_dir(), src))
@@ -334,7 +334,7 @@ int dummy;
                 if self.environment.is_header(src):
                     header_deps.append(src)
                 else:
-                    obj_list.append(self.generate_single_compile(target, outfile, src, True, [], header_deps))
+                    obj_list.append(self.generate_single_compile(target, outfile, src, 'vala', [], header_deps))
         # Generate compile targets for all the pre-existing sources for this target
         for src in target.get_sources():
             if src.endswith('.vala'):
@@ -1614,7 +1614,11 @@ rule FORTRAN_DEP_HACK
                 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)
+        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()

mesonbuild/compilers.py

@@ -473,6 +473,10 @@ class CCompiler(Compiler):
     def get_warn_args(self, level):
         return self.warn_args[level]
 
+    def get_no_warn_args(self):
+        # Almost every compiler uses this for disabling warnings
+        return ['-w']
+
     def get_soname_args(self, prefix, shlib_name, suffix, path, soversion):
         return []
 
@@ -2255,6 +2259,9 @@ end program prog
     def get_warn_args(self, level):
         return ['-Wall']
 
+    def get_no_warn_args(self):
+        return ['-w']
+
 
 class GnuFortranCompiler(FortranCompiler):
     def __init__(self, exelist, version, gcc_type, is_cross, exe_wrapper=None, defines=None):
@@ -2292,6 +2299,10 @@ class G95FortranCompiler(FortranCompiler):
     def get_always_args(self):
         return ['-pipe']
 
+    def get_no_warn_args(self):
+        # FIXME: Confirm that there's no compiler option to disable all warnings
+        return []
+
     def gen_import_library_args(self, implibname):
         """
         The name of the outputted import library
@@ -2357,6 +2368,9 @@ class PGIFortranCompiler(FortranCompiler):
     def get_warn_args(self, level):
         return PGIFortranCompiler.std_warn_args
 
+    def get_no_warn_args(self):
+        return ['-silent']
+
 
 class Open64FortranCompiler(FortranCompiler):
     std_warn_args = ['-fullwarn']