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>

diff --git a/configure b/configure
index c5069775db447327a20b391d6ee491b00ed50efb..3e3c0f36c906a1b147e10ee12cd35630c85d3c86 100755 (executable)
--- a/configure
+++ b/configure
@@ -75,7 +75,6 @@ fi
 TMPB="qemu-conf"
 TMPC="${TMPDIR1}/${TMPB}.c"
 TMPO="${TMPDIR1}/${TMPB}.o"
-TMPCXX="${TMPDIR1}/${TMPB}.cxx"
 TMPM="${TMPDIR1}/${TMPB}.m"
 TMPE="${TMPDIR1}/${TMPB}.exe"
 
@@ -158,10 +157,6 @@ do_cc() {
     do_compiler_werror "$cc" $CPU_CFLAGS "$@"
 }
 
-do_cxx() {
-    do_compiler_werror "$cxx" $CPU_CFLAGS "$@"
-}
-
 do_objc() {
     do_compiler_werror "$objcc" $CPU_CFLAGS "$@"
 }
@@ -171,24 +166,6 @@ add_to() {
     eval $1=\${$1:+\"\$$1 \"}\$2
 }
 
-update_cxxflags() {
-    # Set QEMU_CXXFLAGS from QEMU_CFLAGS by filtering out those
-    # options which some versions of GCC's C++ compiler complain about
-    # because they only make sense for C programs.
-    QEMU_CXXFLAGS="-D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS"
-    CONFIGURE_CXXFLAGS=$(echo "$CONFIGURE_CFLAGS" | sed s/-std=gnu11/-std=gnu++11/)
-    for arg in $QEMU_CFLAGS; do
-        case $arg in
-            -Wstrict-prototypes|-Wmissing-prototypes|-Wnested-externs|\
-            -Wold-style-declaration|-Wold-style-definition|-Wredundant-decls)
-                ;;
-            *)
-                QEMU_CXXFLAGS=${QEMU_CXXFLAGS:+$QEMU_CXXFLAGS }$arg
-                ;;
-        esac
-    done
-}
-
 compile_object() {
   local_cflags="$1"
   do_cc $CFLAGS $EXTRA_CFLAGS $CONFIGURE_CFLAGS $QEMU_CFLAGS $local_cflags -c -o $TMPO $TMPC
@@ -2362,38 +2339,6 @@ fi
 #######################################
 # generate config-host.mak
 
-# Check that the C++ compiler exists and works with the C compiler.
-# All the QEMU_CXXFLAGS are based on QEMU_CFLAGS. Keep this at the end to don't miss any other that could be added.
-if has $cxx; then
-    cat > $TMPC <<EOF
-int c_function(void);
-int main(void) { return c_function(); }
-EOF
-
-    compile_object
-
-    cat > $TMPCXX <<EOF
-extern "C" {
-   int c_function(void);
-}
-int c_function(void) { return 42; }
-EOF
-
-    update_cxxflags
-
-    if do_cxx $CXXFLAGS $EXTRA_CXXFLAGS $CONFIGURE_CXXFLAGS $QEMU_CXXFLAGS -o $TMPE $TMPCXX $TMPO $QEMU_LDFLAGS; then
-        # C++ compiler $cxx works ok with C compiler $cc
-        :
-    else
-        echo "C++ compiler $cxx does not work with C compiler $cc"
-        echo "Disabling C++ specific optional code"
-        cxx=
-    fi
-else
-    echo "No C++ compiler available; disabling C++ specific optional code"
-    cxx=
-fi
-
 if ! (GIT="$git" "$source_path/scripts/git-submodule.sh" "$git_submodules_action" "$git_submodules"); then
     exit 1
 fi
@@ -2474,7 +2419,6 @@ echo "MESON=$meson" >> $config_host_mak
 echo "NINJA=$ninja" >> $config_host_mak
 echo "CC=$cc" >> $config_host_mak
 echo "QEMU_CFLAGS=$QEMU_CFLAGS" >> $config_host_mak
-echo "QEMU_CXXFLAGS=$QEMU_CXXFLAGS" >> $config_host_mak
 echo "QEMU_OBJCFLAGS=$QEMU_OBJCFLAGS" >> $config_host_mak
 echo "GLIB_CFLAGS=$glib_cflags" >> $config_host_mak
 echo "GLIB_LIBS=$glib_libs" >> $config_host_mak
@@ -2665,7 +2609,6 @@ if test "$skip_meson" = no; then
       echo "${a}-softmmu = '$c'" >> $cross
   done
 
-  test -z "$cxx" && echo "link_language = 'c'" >> $cross
   echo "[built-in options]" >> $cross
   echo "c_args = [$(meson_quote $CFLAGS $EXTRA_CFLAGS)]" >> $cross
   echo "cpp_args = [$(meson_quote $CXXFLAGS $EXTRA_CXXFLAGS)]" >> $cross

diff --git a/meson.build b/meson.build
index 780654b00c788689dfa587ba9da4e00b08abc576..9c57ebdfb99d823c17a539ecda53687c82af2d30 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -180,7 +180,6 @@ endif
 ##################
 
 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 @@ endif
 
 if get_option('gprof')
   qemu_cflags += ['-p']
-  qemu_cxxflags += ['-p']
   qemu_objcflags += ['-p']
   qemu_ldflags += ['-p']
 endif
@@ -240,8 +238,33 @@ if get_option('fuzzing')
 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 @@ add_project_arguments('-iquote', '.',
                       '-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

diff --git a/scripts/main.c b/scripts/main.c
new file mode 100644 (file)
index 0000000..b552c8e
--- /dev/null
+++ b/scripts/main.c
@@ -0,0 +1 @@
+int main(void) {}