do not use add_global_arguments to allow subproject use

examples/meson.build

@@ -20,6 +20,7 @@ foreach example: libostd_examples_src
         [example],
         dependencies: [libostd, thread_dep],
         include_directories: libostd_includes,
+        cpp_args: extra_cxxflags,
         install: false
     )
 endforeach

meson.build

@@ -17,17 +17,19 @@ libostd_includes = [include_directories('.')]
 
 cxx = meson.get_compiler('cpp')
 
+extra_cxxflags = []
+
 if get_option('buildtype') != 'plain'
     if cxx.has_argument('-Wshadow')
-        add_global_arguments('-Wshadow', language: 'cpp')
+        extra_cxxflags += '-Wshadow'
     endif
     if cxx.has_argument('-Wold-style-cast')
-        add_global_arguments('-Wold-style-cast', language: 'cpp')
+        extra_cxxflags += '-Wold-style-cast'
     endif
 endif
 
 if cxx.has_argument('-fvisibility=hidden')
-    add_global_arguments('-fvisibility=hidden', language: 'cpp')
+    extra_cxxflags += '-fvisibility=hidden'
 endif
 
 subdir('src')

src/meson.build

@@ -49,7 +49,7 @@ thread_dep = dependency('threads')
 libostd_gen_unicode_exe = executable('gen_unicode',
     ['../gen_unicode.cc'],
     include_directories: libostd_includes,
-    cpp_args: ['-DOSTD_GEN_UNICODE_BUILD'],
+    cpp_args: ['-DOSTD_GEN_UNICODE_BUILD'] + extra_cxxflags,
     install: false,
     native: true
 )
@@ -70,6 +70,7 @@ libostd_lib = both_libraries('ostd',
     libostd_src, libostd_extra_src,
     dependencies: thread_dep,
     include_directories: libostd_includes + [include_directories('.')],
+    cpp_args: extra_cxxflags,
     install: true,
     version: meson.project_version()
 )

tests/meson.build

@@ -2,6 +2,7 @@ test_runner_exe = executable('test_runner',
     ['test_runner.cc'],
     dependencies: libostd,
     include_directories: libostd_includes,
+    cpp_args: extra_cxxflags,
     install: false
 )
 
@@ -39,6 +40,7 @@ foreach test_idx: libostd_tests_indices
         [libostd_tests_src[test_idx]],
         dependencies: libostd,
         include_directories: libostd_includes,
+        cpp_args: extra_cxxflags,
         install: false
     )
 endforeach