Squashed 'src/c-stdaux/' changes from 9582a563c25e..f20e1cf2dfb1

f20e1cf2dfb1 build: verify cflags do not contain spaces
5333735eeb74 build: export cflags via declare_dependency()
d050374b1c1a build: export basic CFLAGS

git-subtree-dir: src/c-stdaux
git-subtree-split: f20e1cf2dfb177e77cc946331ed2d2a83169d8b9

meson.build

@@ -10,9 +10,76 @@ project(
 major = meson.project_version().split('.')[0]
 project_description = 'Auxiliary macros and functions for the C standard library'
 
-add_project_arguments('-D_GNU_SOURCE', language: 'c')
 mod_pkgconfig = import('pkgconfig')
 
+#
+# CFLAGS
+#
+# We have a set of compiler flags for GCC and CLANG which adjust their warnings
+# and behavior to our coding-style.
+#
+# This variable is exported to dependent projects via meson for them to use as
+# well. Since these exports are limited to strings, we need to be careful that
+# the individual entries do not contain spaces (see the assertion below).
+#
+cflags = meson.get_compiler('c').get_supported_arguments(
+        # Enable GNU features of our dependencies. See feature_test_macros(7).
+        '-D_GNU_SOURCE',
+
+        # Prevent CLANG from complaining that alignof-expressions are GNU-only.
+        '-Wno-gnu-alignof-expression',
+        # Never complain about *MAYBE* uninit variables. This is very flaky and
+        # produces bogus results with LTO.
+        '-Wno-maybe-uninitialized',
+        # Do not complain about unknown GCC/CLANG warnings.
+        '-Wno-unknown-warning-option',
+        # There is no standardized way to mark unused arguments, so never
+        # complain about them.
+        '-Wno-unused-parameter',
+
+        # Preprocessor evaluations often lead to warnings about comparisons
+        # that are always true/false. Make sure they do not break a build but
+        # keep them on for diagnostics.
+        '-Wno-error=type-limits',
+        # As we use designated field-initializers, this warning should never
+        # trigger, but still does on GCC in combination with some other
+        # preprocessor checks. Lets just make sure it does not break builds.
+        '-Wno-error=missing-field-initializers',
+
+        # Warn if we ever use `__DATE__` and similar in our build. We want
+        # reproducible builds.
+        '-Wdate-time',
+        # We strictly follow decl-before-statements, so check it.
+        '-Wdeclaration-after-statement',
+        # More strict logical-op sanity checks.
+        '-Wlogical-op',
+        # Loudly complain about missing include-directories.
+        '-Wmissing-include-dirs',
+        # We want hints about noreturn functions, so warn about them.
+        '-Wmissing-noreturn',
+        # Warn if an extern-decl is inside a function. We want imports as
+        # global attributes, never as local ones.
+        '-Wnested-externs',
+        # Warn about redundant declarations. We want declarations in headers
+        # and want them to be unique.
+        '-Wredundant-decls',
+        # Warn about shadowed variables so we do not accidentally override
+        # variables of parent scopes and thus confuse macros.
+        '-Wshadow',
+        # Warn about aliasing violations. Level-3 produces the least false
+        # positives, but is the slowest. Force it to avoid breaking -Werror
+        # builds.
+        '-Wstrict-aliasing=3',
+        # Suggest 'noreturn' attributes. They are useful, we want them!
+        '-Wsuggest-attribute=noreturn',
+        # Warn about undefined identifiers in preprocessor conditionals.
+        '-Wundef',
+        # Make sure literal strings are considered 'const'.
+        '-Wwrite-strings',
+)
+assert(not ''.join(cflags).contains(' '), 'Malformed compiler flags.')
+add_project_arguments(cflags, language: 'c')
+
 subdir('src')
 
 meson.override_dependency('libcstdaux-'+major, libcstdaux_dep, static: true)

src/meson.build

@@ -6,6 +6,7 @@
 
 libcstdaux_dep = declare_dependency(
         include_directories: include_directories('.'),
+        variables: { 'cflags': ' '.join(cflags) },
         version: meson.project_version(),
 )