[gnome-software] meson: make two compiler warnings fatal

[Richard Hughes <rhughes src gnome org>]

commit 4115298657a592e827c686ea3a7803103771ff8d
Author: Will Thompson <will willthompson co uk>
Date:   Fri Nov 15 15:13:24 2019 +0000

    meson: make two compiler warnings fatal
    
    I wasted the best part of an hour this morning because I didn't notice
    the following warnings (from Endless's branch):
    
        ../plugins/eos-blacklist/gs-plugin-eos-blacklist.c: In function 'gs_plugin_setup':
        ../plugins/eos-blacklist/gs-plugin-eos-blacklist.c:193:36: warning: implicit declaration of function 
'flatpak_installation_get_default_locales'; did you mean 'flatpak_installation_get_default_languages'? 
[-Wimplicit-function-declaration]
            priv->flatpak_default_locales = flatpak_installation_get_default_locales (priv->installation, 
&local_error);
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                            flatpak_installation_get_default_languages
        ../plugins/eos-blacklist/gs-plugin-eos-blacklist.c:193:36: warning: nested extern declaration of 
'flatpak_installation_get_default_locales' [-Wnested-externs]
        ../plugins/eos-blacklist/gs-plugin-eos-blacklist.c:193:34: warning: assignment to 'char **' from 
'int' makes pointer from integer without a cast [-Wint-conversion]
            priv->flatpak_default_locales = flatpak_installation_get_default_locales (priv->installation, 
&local_error);
    
    My Flatpak headers were older than my Flatpak shared library, which did
    define the 'flatpak_installation_get_default_locales' symbol. The
    default return type, int, is narrower than a pointer on x86_64 so the
    pointer was truncated and this would crash at runtime.
    
    Of course, I could have passed `-Dwerror=true` to Meson but I believe
    that implicit-function-declaration and nested-externs should always be
    fatal, regardless of that setting.
    
    Another option would be to add 'werror=true' to default_options, but I
    think this is bad practice: a new compiler version could cause perfectly
    good code to stop compiling.

 meson.build | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/meson.build b/meson.build
index bae72315..3a506b6a 100644
--- a/meson.build
+++ b/meson.build
@@ -34,6 +34,7 @@ test_args = [
   '-Wformat-signedness',
   '-Wignored-qualifiers',
   '-Wimplicit-function-declaration',
+  '-Werror=implicit-function-declaration',
   '-Winit-self',
   '-Winline',
   '-Wmissing-declarations',
@@ -43,6 +44,7 @@ test_args = [
   '-Wmissing-parameter-type',
   '-Wmissing-prototypes',
   '-Wnested-externs',
+  '-Werror=nested-externs',
   '-Wno-discarded-qualifiers',
   '-Wno-missing-field-initializers',
   '-Wno-strict-aliasing',