meson: fix build without cpp toolchain

We don't need a cpp toolchain for building glib so lets just
automatically disable tests requiring one when not available.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

(cherry-picked from commit d0b9ebbaacb5f69aaaad30829e04cd3a88f084cb)

fuzzing/meson.build

@@ -26,8 +26,12 @@ extra_c_args = cc.get_supported_arguments('-Werror=unused-function')
 
 # Links in a static library provided by oss-fuzz, else a standalone driver.
 # https://google.github.io/oss-fuzz/getting-started/new-project-guide/#buildsh-script-environment
-fuzzing_engine = cxx.find_library('FuzzingEngine', required : get_option('oss_fuzz'))
-if fuzzing_engine.found()
+have_fuzzing_engine = false
+if have_cxx
+  fuzzing_engine = cxx.find_library('FuzzingEngine', required : get_option('oss_fuzz'))
+  have_fuzzing_engine = fuzzing_engine.found()
+endif
+if have_fuzzing_engine
   deps += fuzzing_engine
 else
   extra_sources += 'driver.c'

gio/tests/meson.build

@@ -58,9 +58,6 @@ gio_tests = {
   },
   'converter-stream' : {},
   'credentials' : {},
-  'cxx' : {
-    'source' : ['cxx.cpp'],
-  },
   'data-input-stream' : {},
   'data-output-stream' : {},
   'fileattributematcher' : {},
@@ -124,6 +121,14 @@ gio_tests = {
   'win32-appinfo' : {},
 }
 
+if have_cxx
+  gio_tests += {
+    'cxx' : {
+      'source' : ['cxx.cpp'],
+    },
+  }
+endif
+
 test_extra_programs = {
   'gdbus-connection-flush-helper' : {},
   'gdbus-testserver' : {},

glib/tests/meson.build

@@ -15,9 +15,6 @@ glib_tests = {
   'completion' : {},
   'cond' : {},
   'convert' : {},
-  'cxx' : {
-    'source' : ['cxx.cpp'],
-  },
   'dataset' : {},
   'date' : {
     # FIXME: https://gitlab.gnome.org/GNOME/glib/-/issues/1392
@@ -142,6 +139,14 @@ glib_tests = {
   },
 }
 
+if have_cxx
+  glib_tests += {
+    'cxx' : {
+      'source' : ['cxx.cpp'],
+    }
+  }
+endif
+
 if cc.get_id() != 'msvc'
   glib_tests += {'autoptr' : {}}
 endif

gmodule/tests/meson.build

@@ -1,8 +1,10 @@
-gmodule_tests = {
-  'cxx' : {
-    'source' : ['cxx.cpp'],
-  },
-}
+if have_cxx
+  gmodule_tests = {
+    'cxx' : {
+      'source' : ['cxx.cpp'],
+    },
+  }
+endif
 
 test_env = environment()
 test_env.set('G_TEST_SRCDIR', meson.current_source_dir())

gobject/tests/meson.build

@@ -29,9 +29,6 @@ marshalers_c = custom_target('marshalers_c',
 gobject_tests = {
   'qdata' : {},
   'boxed' : {},
-  'cxx' : {
-    'source' : ['cxx.cpp'],
-  },
   'enums' : {},
   'param' : {},
   'threadtests' : {},
@@ -59,6 +56,14 @@ gobject_tests = {
   'type-flags' : {},
 }
 
+if have_cxx
+  gobject_tests += {
+    'cxx' : {
+      'source' : ['cxx.cpp'],
+    },
+  }
+endif
+
 if cc.get_id() != 'msvc'
   gobject_tests += {'autoptr' : {}}
 endif

meson.build

@@ -1,4 +1,4 @@
-project('glib', 'c', 'cpp',
+project('glib', 'c',
   version : '2.72.3',
   # NOTE: We keep this pinned at 0.52 because that's what Debian Stable ships
   meson_version : '>= 0.52.0',
@@ -10,7 +10,14 @@ project('glib', 'c', 'cpp',
 )
 
 cc = meson.get_compiler('c')
-cxx = meson.get_compiler('cpp')
+if meson.version().version_compare('>= 0.54.0')
+  have_cxx = add_languages('cpp', native: false, required: get_option('oss_fuzz').enabled())
+else
+  have_cxx = add_languages('cpp', required: get_option('oss_fuzz').enabled())
+endif
+if have_cxx
+  cxx = meson.get_compiler('cpp')
+endif
 
 cc_can_run = not meson.is_cross_build() or meson.has_exe_wrapper()
 
@@ -495,7 +502,9 @@ else
 endif
 
 add_project_arguments(cc.get_supported_arguments(warning_c_args), language: 'c')
-add_project_arguments(cxx.get_supported_arguments(warning_cxx_args), language: 'cpp')
+if have_cxx
+  add_project_arguments(cxx.get_supported_arguments(warning_cxx_args), language: 'cpp')
+endif
 
 # FIXME: We cannot build some of the GResource tests with -z nodelete, which
 # means we cannot use that flag in add_project_link_arguments(), and must add
@@ -1734,18 +1743,20 @@ if g_have_iso_c_varargs
 #endif''')
 endif
 
-g_have_iso_cxx_varargs = cxx.compiles('''
-  void some_func (void) {
-    int a(int p1, int p2, int p3);
-    #define call_a(...) a(1,__VA_ARGS__)
-    call_a(2,3);
-  }''', name : 'ISO C99 varargs macros in C++')
+if have_cxx
+  g_have_iso_cxx_varargs = cxx.compiles('''
+    void some_func (void) {
+      int a(int p1, int p2, int p3);
+      #define call_a(...) a(1,__VA_ARGS__)
+      call_a(2,3);
+    }''', name : 'ISO C99 varargs macros in C++')
 
-if g_have_iso_cxx_varargs
-  glibconfig_conf.set('g_have_iso_cxx_varargs', '''
-#ifdef __cplusplus
-# define G_HAVE_ISO_VARARGS 1
-#endif''')
+  if g_have_iso_cxx_varargs
+    glibconfig_conf.set('g_have_iso_cxx_varargs', '''
+  #ifdef __cplusplus
+  # define G_HAVE_ISO_VARARGS 1
+  #endif''')
+  endif
 endif
 
 g_have_gnuc_varargs = cc.compiles('''