meson: prepare move of QEMU_CFLAGS to meson

Clean up the handling of compiler flags in meson.build, splitting
the general flags that should be included in subprojects as well,
from warning flags that only apply to QEMU itself.  The two were
mixed in both configure tests and meson tests.

This split makes it easier to move the compiler tests piecewise
from configure to Meson.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -190,10 +190,23 @@ endif
 # Compiler flags #
 ##################
 
-qemu_cflags = config_host['QEMU_CFLAGS'].split()
+qemu_common_flags = []
+qemu_cflags = []
+foreach arg : config_host['QEMU_CFLAGS'].split()
+  if arg.startswith('-W')
+    qemu_cflags += arg
+  else
+    qemu_common_flags += arg
+  endif
+endforeach
 qemu_objcflags = config_host['QEMU_OBJCFLAGS'].split()
 qemu_ldflags = config_host['QEMU_LDFLAGS'].split()
 
+if get_option('gprof')
+  qemu_common_flags += ['-p']
+  qemu_ldflags += ['-p']
+endif
+
 if get_option('prefer_static')
   qemu_ldflags += get_option('b_pie') ? '-static-pie' : '-static'
 endif
@@ -207,10 +220,9 @@ if targetos == 'windows'
   qemu_ldflags += cc.get_supported_link_arguments('-Wl,--dynamicbase', '-Wl,--high-entropy-va')
 endif
 
-if get_option('gprof')
-  qemu_cflags += ['-p']
-  qemu_objcflags += ['-p']
-  qemu_ldflags += ['-p']
+# Exclude --warn-common with TSan to suppress warnings from the TSan libraries.
+if targetos != 'sunos' and not config_host.has_key('CONFIG_TSAN')
+  qemu_ldflags += cc.get_supported_link_arguments('-Wl,--warn-common')
 endif
 
 # Specify linker-script with add_project_link_arguments so that it is not placed
@@ -226,19 +238,16 @@ if get_option('fuzzing')
                   name: '-fsanitize-coverage-allowlist=/dev/null',
                  args: ['-fsanitize-coverage-allowlist=/dev/null',
                         '-fsanitize-coverage=trace-pc'] )
-    add_global_arguments('-fsanitize-coverage-allowlist=instrumentation-filter',
-                         native: false, language: all_languages)
+    qemu_common_flags += ['-fsanitize-coverage-allowlist=instrumentation-filter']
   endif
 
   if get_option('fuzzing_engine') == ''
     # Add CFLAGS to tell clang to add fuzzer-related instrumentation to all the
     # compiled code.  To build non-fuzzer binaries with --enable-fuzzing, link
     # everything with fsanitize=fuzzer-no-link. Otherwise, the linker will be
     # unable to bind the fuzzer-related callbacks added by instrumentation.
-    add_global_arguments('-fsanitize=fuzzer-no-link',
-                         native: false, language: all_languages)
-    add_global_link_arguments('-fsanitize=fuzzer-no-link',
-                              native: false, language: all_languages)
+    qemu_common_flags += ['-fsanitize=fuzzer-no-link']
+    qemu_ldflags += ['-fsanitize=fuzzer-no-link']
     # For the actual fuzzer binaries, we need to link against the libfuzzer
     # library. They need to be configurable, to support OSS-Fuzz
     fuzz_exe_ldflags = ['-fsanitize=fuzzer']
@@ -249,6 +258,9 @@ if get_option('fuzzing')
   endif
 endif
 
+add_global_arguments(qemu_common_flags, native: false, language: all_languages)
+add_global_link_arguments(qemu_ldflags, native: false, language: all_languages)
+
 # Check that the C++ compiler exists and works with the C compiler.
 link_language = 'c'
 linker = cc
@@ -272,16 +284,9 @@ if 'cpp' in all_languages
   endif
 endif
 
-# Exclude --warn-common with TSan to suppress warnings from the TSan libraries.
-if targetos != 'sunos' and not config_host.has_key('CONFIG_TSAN')
-  qemu_ldflags += linker.get_supported_link_arguments('-Wl,--warn-common')
-endif
-
-add_global_link_arguments(qemu_ldflags, native: false, language: all_languages)
-
-add_global_arguments(qemu_cflags, native: false, language: 'c')
-add_global_arguments(qemu_cxxflags, native: false, language: 'cpp')
-add_global_arguments(qemu_objcflags, native: false, language: 'objc')
+add_project_arguments(qemu_cflags, native: false, language: 'c')
+add_project_arguments(qemu_cxxflags, native: false, language: 'cpp')
+add_project_arguments(qemu_objcflags, native: false, language: 'objc')
 if targetos == 'linux'
   add_project_arguments('-isystem', meson.current_source_dir() / 'linux-headers',
                         '-isystem', 'linux-headers',
@@ -3844,12 +3849,12 @@ link_args = get_option(link_language + '_link_args')
 if link_args.length() > 0
   summary_info += {'LDFLAGS':         ' '.join(link_args)}
 endif
-summary_info += {'QEMU_CFLAGS':       ' '.join(qemu_cflags)}
+summary_info += {'QEMU_CFLAGS':       ' '.join(qemu_common_flags + qemu_cflags)}
 if 'cpp' in all_languages
-  summary_info += {'QEMU_CXXFLAGS':     ' '.join(qemu_cxxflags)}
+  summary_info += {'QEMU_CXXFLAGS':     ' '.join(qemu_common_flags + qemu_cxxflags)}
 endif
 if 'objc' in all_languages
-  summary_info += {'QEMU_OBJCFLAGS':    ' '.join(qemu_objcflags)}
+  summary_info += {'QEMU_OBJCFLAGS':    ' '.join(qemu_common_flags + qemu_objcflags)}
 endif
 summary_info += {'QEMU_LDFLAGS':      ' '.join(qemu_ldflags)}
 summary_info += {'profiler':          get_option('profiler')}