commit b485458e00dae4af5e2b7b1c17521e2885180544
author Paolo Bonzini <pbonzini@redhat.com> Mon Nov 08 12:31:52 2021 +0100
committer Paolo Bonzini <pbonzini@redhat.com> Sat Oct 01 21:16:36 2022 +0200
tree a53770c1c583dc48a3844e83e1a3e2f0d97e2907
parent 6d3226357fb848499aacf609bf628932bca781ea

configure, meson: move C++ compiler detection to meson.build

The test is slightly weaker than before, because it does not
call an extern "C" function from a C source file.  However,
in practice what we seek to detect is ABI compatibility of the
various sanitizer flags, and for that it is enough to compile
anything with CC and link it with CXX.

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

meson.build

diff --git a/meson.build b/meson.build
index 780654b..9c57ebd 100644
--- a/meson.build
+++ b/meson.build
@@ -180,7 +180,6 @@
 ##################
 
 qemu_cflags = config_host['QEMU_CFLAGS'].split()
-qemu_cxxflags = config_host['QEMU_CXXFLAGS'].split()
 qemu_objcflags = config_host['QEMU_OBJCFLAGS'].split()
 qemu_ldflags = config_host['QEMU_LDFLAGS'].split()
 
@@ -194,7 +193,6 @@
 
 if get_option('gprof')
   qemu_cflags += ['-p']
-  qemu_cxxflags += ['-p']
   qemu_objcflags += ['-p']
   qemu_ldflags += ['-p']
 endif
@@ -240,8 +238,33 @@
 endif
 
 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'])
+
+# Check that the C++ compiler exists and works with the C compiler.
+link_language = 'c'
+linker = cc
+qemu_cxxflags = []
+if add_languages('cpp', required: false, native: false)
+  cxx = meson.get_compiler('cpp')
+  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
+  add_global_arguments(qemu_cxxflags, native: false, language: 'cpp')
+
+  if cxx.links(files('scripts/main.c'), args: qemu_cflags)
+    link_language = 'cpp'
+    linker = cxx
+  else
+    message('C++ compiler does not work with C compiler')
+    message('Disabling C++-specific optional code')
+  endif
+endif
+
 add_global_link_arguments(qemu_ldflags, native: false, language: ['c', 'cpp', 'objc'])
 
 if targetos == 'linux'
@@ -255,14 +278,6 @@
                       '-iquote', meson.current_source_dir() / 'include',
                       language: ['c', 'cpp', 'objc'])
 
-link_language = meson.get_external_property('link_language', 'cpp')
-if link_language == 'cpp'
-  add_languages('cpp', required: true, native: false)
-  cxx = meson.get_compiler('cpp')
-  linker = cxx
-else
-  linker = cc
-endif
 if host_machine.system() == 'darwin'
   add_languages('objc', required: false, native: false)
 endif