[PATCH 25/30] build: move warning flag selection to meson

[Paolo Bonzini <pbonzini@redhat.com>]

Meson already knows to test with the positive form of the flag, which
simplifies the test.  Warnings are now tested explicitly for the C++
compiler, instead of hardcoding those that are only available for
the C language.

At this point all compiler flags in QEMU_CFLAGS are global and only
depend on the OS.  No feature tests are performed in configure.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 configure                | 94 ----------------------------------------
 contrib/plugins/Makefile |  3 +-
 meson.build              | 72 ++++++++++++++++++++----------
 3 files changed, 51 insertions(+), 118 deletions(-)

diff --git a/configure b/configure
index 5d31294f316f..6df61f4337e4 100755
--- a/configure
+++ b/configure
@@ -75,7 +75,6 @@ fi
 TMPB="qemu-conf"
 TMPC="${TMPDIR1}/${TMPB}.c"
 TMPO="${TMPDIR1}/${TMPB}.o"
-TMPM="${TMPDIR1}/${TMPB}.m"
 TMPE="${TMPDIR1}/${TMPB}.exe"
 
 rm -f config.log
@@ -157,15 +156,6 @@ do_cc() {
     do_compiler_werror "$cc" $CPU_CFLAGS "$@"
 }
 
-do_objc() {
-    do_compiler_werror "$objcc" $CPU_CFLAGS "$@"
-}
-
-# Append $2 to the variable named $1, with space separation
-add_to() {
-    eval $1=\${$1:+\"\$$1 \"}\$2
-}
-
 compile_object() {
   local_cflags="$1"
   do_cc $CFLAGS $EXTRA_CFLAGS $CONFIGURE_CFLAGS $QEMU_CFLAGS $local_cflags -c -o $TMPO $TMPC
@@ -1091,89 +1081,6 @@ if ! compile_prog "" "" ; then
     error_exit "You need at least GCC v7.4 or Clang v6.0 (or XCode Clang v10.0)"
 fi
 
-# Accumulate -Wfoo and -Wno-bar separately.
-# We will list all of the enable flags first, and the disable flags second.
-# Note that we do not add -Werror, because that would enable it for all
-# configure tests. If a configure test failed due to -Werror this would
-# just silently disable some features, so it's too error prone.
-
-warn_flags=
-add_to warn_flags -Wundef
-add_to warn_flags -Wwrite-strings
-add_to warn_flags -Wmissing-prototypes
-add_to warn_flags -Wstrict-prototypes
-add_to warn_flags -Wredundant-decls
-add_to warn_flags -Wold-style-declaration
-add_to warn_flags -Wold-style-definition
-add_to warn_flags -Wtype-limits
-add_to warn_flags -Wformat-security
-add_to warn_flags -Wformat-y2k
-add_to warn_flags -Winit-self
-add_to warn_flags -Wignored-qualifiers
-add_to warn_flags -Wempty-body
-add_to warn_flags -Wnested-externs
-add_to warn_flags -Wendif-labels
-add_to warn_flags -Wexpansion-to-defined
-add_to warn_flags -Wimplicit-fallthrough=2
-
-nowarn_flags=
-add_to nowarn_flags -Wno-initializer-overrides
-add_to nowarn_flags -Wno-missing-include-dirs
-add_to nowarn_flags -Wno-shift-negative-value
-add_to nowarn_flags -Wno-string-plus-int
-add_to nowarn_flags -Wno-typedef-redefinition
-add_to nowarn_flags -Wno-tautological-type-limit-compare
-add_to nowarn_flags -Wno-psabi
-add_to nowarn_flags -Wno-gnu-variable-sized-type-not-at-end
-
-gcc_flags="$warn_flags $nowarn_flags"
-
-cc_has_warning_flag() {
-    write_c_skeleton;
-
-    # Use the positive sense of the flag when testing for -Wno-wombat
-    # support (gcc will happily accept the -Wno- form of unknown
-    # warning options).
-    optflag="$(echo $1 | sed -e 's/^-Wno-/-W/')"
-    compile_prog "-Werror $optflag" ""
-}
-
-objcc_has_warning_flag() {
-    cat > $TMPM <<EOF
-int main(void) { return 0; }
-EOF
-
-    # Use the positive sense of the flag when testing for -Wno-wombat
-    # support (gcc will happily accept the -Wno- form of unknown
-    # warning options).
-    optflag="$(echo $1 | sed -e 's/^-Wno-/-W/')"
-    do_objc -Werror $optflag \
-      $OBJCFLAGS $EXTRA_OBJCFLAGS $CONFIGURE_OBJCFLAGS $QEMU_OBJCFLAGS \
-      -o $TMPE $TMPM
-}
-
-for flag in $gcc_flags; do
-    if cc_has_warning_flag $flag ; then
-        QEMU_CFLAGS="$QEMU_CFLAGS $flag"
-    fi
-    if objcc_has_warning_flag $flag ; then
-        QEMU_OBJCFLAGS="$QEMU_OBJCFLAGS $flag"
-    fi
-done
-
-# Disable -Wmissing-braces on older compilers that warn even for
-# the "universal" C zero initializer {0}.
-cat > $TMPC << EOF
-struct {
-  int a[2];
-} x = {0};
-EOF
-if compile_object "-Werror" "" ; then
-  :
-else
-  QEMU_CFLAGS="$QEMU_CFLAGS -Wno-missing-braces"
-fi
-
 # Resolve default for --enable-plugins
 if test "$static" = "yes" ; then
   if test "$plugins" = "yes"; then
@@ -1928,7 +1835,6 @@ echo "NINJA=$ninja" >> $config_host_mak
 echo "PKG_CONFIG=${pkg_config_exe}" >> $config_host_mak
 echo "CC=$cc" >> $config_host_mak
 echo "QEMU_CFLAGS=$QEMU_CFLAGS" >> $config_host_mak
-echo "QEMU_OBJCFLAGS=$QEMU_OBJCFLAGS" >> $config_host_mak
 echo "EXESUF=$EXESUF" >> $config_host_mak
 
 # use included Linux headers
diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile
index 8a316cd76f2f..b2b9db9f51af 100644
--- a/contrib/plugins/Makefile
+++ b/contrib/plugins/Makefile
@@ -27,8 +27,7 @@ SONAMES := $(addsuffix .so,$(addprefix lib,$(NAMES)))
 # The main QEMU uses Glib extensively so it's perfectly fine to use it
 # in plugins (which many example do).
 CFLAGS := $(shell $(PKG_CONFIG) --cflags glib-2.0)
-CFLAGS += -fPIC -Wall $(filter -W%, $(QEMU_CFLAGS))
-CFLAGS += $(if $(findstring no-psabi,$(QEMU_CFLAGS)),-Wpsabi)
+CFLAGS += -fPIC -Wall
 CFLAGS += $(if $(CONFIG_DEBUG_TCG), -ggdb -O0)
 CFLAGS += -I$(SRC_PATH)/include/qemu
 
diff --git a/meson.build b/meson.build
index c5a8dce9e1d6..4ec8104b73a3 100644
--- a/meson.build
+++ b/meson.build
@@ -190,16 +190,8 @@ endif
 # Compiler flags #
 ##################
 
-qemu_common_flags = []
+qemu_common_flags = config_host['QEMU_CFLAGS'].split()
 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 = []
 
 if get_option('gprof')
@@ -380,20 +372,49 @@ endif
 add_global_arguments(qemu_common_flags, native: false, language: all_languages)
 add_global_link_arguments(qemu_ldflags, native: false, language: all_languages)
 
+# Collect warnings that we want to enable
+
+warn_flags = [
+  '-Wundef',
+  '-Wwrite-strings',
+  '-Wmissing-prototypes',
+  '-Wstrict-prototypes',
+  '-Wredundant-decls',
+  '-Wold-style-declaration',
+  '-Wold-style-definition',
+  '-Wtype-limits',
+  '-Wformat-security',
+  '-Wformat-y2k',
+  '-Winit-self',
+  '-Wignored-qualifiers',
+  '-Wempty-body',
+  '-Wnested-externs',
+  '-Wendif-labels',
+  '-Wexpansion-to-defined',
+  '-Wimplicit-fallthrough=2',
+  '-Wno-initializer-overrides',
+  '-Wno-missing-include-dirs',
+  '-Wno-shift-negative-value',
+  '-Wno-string-plus-int',
+  '-Wno-typedef-redefinition',
+  '-Wno-tautological-type-limit-compare',
+  '-Wno-psabi',
+  '-Wno-gnu-variable-sized-type-not-at-end',
+]
+
+if not cc.compiles('''
+  struct {
+    int a[2];
+  } x = {0};''', args: ['-Werror'])
+  warn_flags += ['-Wno-missing-braces']
+endif
+
 # Check that the C++ compiler exists and works with the C compiler.
 link_language = 'c'
 linker = cc
 qemu_cxxflags = []
 if 'cpp' in all_languages
-  add_global_arguments(['-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-D__STDC_FORMAT_MACROS'],
-                       native: false, language: 'cpp')
-  foreach k: qemu_cflags
-    if k not in ['-Wstrict-prototypes', '-Wmissing-prototypes', '-Wnested-externs',
-                 '-Wold-style-declaration', '-Wold-style-definition', '-Wredundant-decls']
-      qemu_cxxflags += [k]
-    endif
-  endforeach
-
+  qemu_cxxflags = ['-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-D__STDC_FORMAT_MACROS'] + qemu_cflags
   if cxx.links(files('scripts/main.c'), args: qemu_cflags)
     link_language = 'cpp'
     linker = cxx
@@ -413,9 +434,16 @@ if get_option('optimization') != '0' and targetos == 'linux'
   endif
 endif
 
-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')
+add_project_arguments(qemu_cflags, native: false, language: 'objc')
+add_project_arguments(cc.get_supported_arguments(warn_flags), native: false, language: 'c')
+if 'cpp' in all_languages
+  add_project_arguments(qemu_cxxflags, native: false, language: 'cpp')
+  add_project_arguments(cxx.get_supported_arguments(warn_flags), native: false, language: 'cpp')
+endif
+if 'objc' in all_languages
+  # Note sanitizer flags are not applied to Objective-C sources!
+  add_project_arguments(objc.get_supported_arguments(warn_flags), native: false, language: 'objc')
+endif
 if targetos == 'linux'
   add_project_arguments('-isystem', meson.current_source_dir() / 'linux-headers',
                         '-isystem', 'linux-headers',
@@ -3927,7 +3955,7 @@ if 'cpp' in all_languages
   summary_info += {'QEMU_CXXFLAGS':     ' '.join(qemu_common_flags + qemu_cxxflags)}
 endif
 if 'objc' in all_languages
-  summary_info += {'QEMU_OBJCFLAGS':    ' '.join(qemu_common_flags + qemu_objcflags)}
+  summary_info += {'QEMU_OBJCFLAGS':    ' '.join(qemu_common_flags)}
 endif
 summary_info += {'QEMU_LDFLAGS':      ' '.join(qemu_ldflags)}
 summary_info += {'profiler':          get_option('profiler')}
-- 
2.38.1