[atkmm/atkmm-2-28] meson.build: Avoid configuration warnings

[Kjell Ahlstedt <kjellahl src gnome org>]

commit d6810722b5c8c5e8fb1ce7ec61d90b961f8935ad
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Sun May 15 16:35:06 2022 +0200

    meson.build: Avoid configuration warnings

 meson.build | 43 ++++++++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 19 deletions(-)
---
diff --git a/meson.build b/meson.build
index 3a7762e..5811538 100644
--- a/meson.build
+++ b/meson.build
@@ -4,7 +4,8 @@ project('atkmm', 'cpp',
   version: '2.28.2',
   license: 'LGPLv2.1+',
   default_options: [
-    'cpp_std=c++11'
+    'cpp_std=c++11',
+    'warning_level=1',
   ],
   meson_version: '>= 0.55.0', # required for meson.add_dist_script(python3, ...)
                               # and meson.add_install_script(python3, ...)
@@ -73,10 +74,12 @@ maintainer_mode = maintainer_mode_opt == 'true' or \
 if is_dist_check
   message('Looks like a tarball is being tested. ' + \
   'Option "dist-warnings" is used instead of "warnings".')
-  warning_level = get_option('dist-warnings')
+  cpp_warnings = get_option('dist-warnings')
 else
-  warning_level = get_option('warnings')
+  cpp_warnings = get_option('warnings')
 endif
+warning_level = get_option('warning_level').to_int()
+werror = get_option('werror')
 build_deprecated_api = get_option('build-deprecated-api')
 build_documentation_opt = get_option('build-documentation')
 build_documentation = build_documentation_opt == 'true' or \
@@ -231,24 +234,25 @@ if is_msvc
 endif
 
 # Set compiler warnings.
+# Meson warns if any of the /W1, /W2, /W3, /W4, /Wall, -Wall, -Wextra, -Werror
+# compiler options are added with add_project_arguments().
+# Avoid such warnings, when possible.
+# See _warn_about_builtin_args() in meson/mesonbuild/interpreter/interpreter.py.
 warning_flags = []
-if warning_level == 'min'
-  if is_msvc
-    warning_flags = ['/W3']
-  else
-    warning_flags = ['-Wall']
+if cpp_warnings == 'min'
+  if warning_level == 0
+    warning_flags = is_msvc ? ['/W2'] : ['-Wall']
   endif
-elif warning_level == 'max' or warning_level == 'fatal'
-  if is_msvc
-    warning_flags = ['/W4']
-  else
-    warning_flags = '-pedantic -Wall -Wextra -Wformat-security -Wsuggest-override -Wshadow 
-Wno-long-long'.split()
+elif cpp_warnings == 'max' or cpp_warnings == 'fatal'
+  if warning_level < 3
+    warning_flags = is_msvc ? ['/W4'] : ['-pedantic', '-Wall', '-Wextra']
   endif
-  if warning_level == 'fatal'
-    if is_msvc
-      warning_flags += ['/WX']
-    else
-      warning_flags += ['-Werror']
+  if not is_msvc
+    warning_flags += '-Wformat-security -Wsuggest-override -Wshadow -Wno-long-long'.split()
+  endif
+  if cpp_warnings == 'fatal'
+    if not werror
+      warning_flags += is_msvc ? ['/WX'] : ['-Werror']
     endif
     deprecations = 'G ATK GLIBMM SIGCXX'.split()
     foreach d : deprecations
@@ -331,7 +335,8 @@ summary = [
   meson.project_name() + ' ' + meson.project_version(),
   '',
   '         Maintainer mode: @0@@1@'.format(maintainer_mode_opt, real_maintainer_mode),
-  '       Compiler warnings: @0@'.format(warning_level),
+  '       Compiler warnings: @0@ (warning_level: @1@, werror: @2@)'. \
+                             format(cpp_warnings, warning_level, werror),
   '    Build deprecated API: @0@'.format(build_deprecated_api),
   'Build HTML documentation: @0@@1@'.format(build_documentation_opt, real_build_documentation),
   'Directories:',