[PATCH v3 1/7] meson: Run some compiler checks using -Wno-unused-value

[Philippe Mathieu-Daudé]

When running Clang static analyzer on macOS I'm getting:

  include/qemu/osdep.h:634:8: error: redefinition of 'iovec'
    634 | struct iovec {
        |        ^
  
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_iovec_t.h:31:8:
 note: previous definition is here
     31 | struct iovec {
        |        ^
  1 error generated.

Looking at meson-logs.txt, the analyzer enables -Wunused-value
making meson generated code to fail:

    Code:
    #include <sys/uio.h>
            void bar(void) {
                sizeof(struct iovec);
            }
    -----------
    stderr:
    meson-private/tmpe8_1b_00/testfile.c:3:13: error: expression result unused 
[-Werror,-Wunused-value]
        3 |             sizeof(struct iovec);
          |             ^~~~~~~~~~~~~~~~~~~~
    1 error generated.
    -----------
    Checking for type "struct iovec" : NO

    Code:
    #include <utmpx.h>
            void bar(void) {
                sizeof(struct utmpx);
            }
    -----------
    stderr:
    meson-private/tmp3n0u490p/testfile.c:3:13: error: expression result unused 
[-Werror,-Wunused-value]
        3 |             sizeof(struct utmpx);
          |             ^~~~~~~~~~~~~~~~~~~~
    1 error generated.
    -----------
    Checking for type "struct utmpx" : NO

    Code:

            #include <getopt.h>
            int main(void) {
                /* If it's not defined as a macro, try to use as a symbol */
                #ifndef optreset
                    optreset;
                #endif
                return 0;
            }
    -----------
    stderr:
    meson-private/tmp1rzob_os/testfile.c:6:17: error: expression result unused 
[-Werror,-Wunused-value]
        6 |                 optreset;
          |                 ^~~~~~~~
    1 error generated.
    -----------
    Header "getopt.h" has symbol "optreset" : NO

    Code:

            #include <vmnet/vmnet.h>
            int main(void) {
                /* If it's not defined as a macro, try to use as a symbol */
                #ifndef VMNET_BRIDGED_MODE
                    VMNET_BRIDGED_MODE;
                #endif
                return 0;
            }
    -----------
    stderr:
    meson-private/tmpl9jgsxpt/testfile.c:6:17: error: expression result unused 
[-Werror,-Wunused-value]
        6 |                 VMNET_BRIDGED_MODE;
          |                 ^~~~~~~~~~~~~~~~~~
    1 error generated.
    -----------
    Header "vmnet/vmnet.h" has symbol "VMNET_BRIDGED_MODE" with dependency 
appleframeworks: NO
    ../meson.build:1174: WARNING: vmnet.framework API is outdated, disabling

Fix by explicitly disabling -Wunused-value from these meson checks.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
RFC: Probably meson should do that in has_header_symbol() / has_type()?
---
 meson.build | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/meson.build b/meson.build
index 85f74854735..9d93dcd95d7 100644
--- a/meson.build
+++ b/meson.build
@@ -1189,7 +1189,8 @@ cocoa = dependency('appleframeworks',
 vmnet = dependency('appleframeworks', modules: 'vmnet', required: 
get_option('vmnet'))
 if vmnet.found() and not cc.has_header_symbol('vmnet/vmnet.h',
                                               'VMNET_BRIDGED_MODE',
-                                              dependencies: vmnet)
+                                              dependencies: vmnet,
+                                              args: '-Wno-unused-value')
   vmnet = not_found
   if get_option('vmnet').enabled()
     error('vmnet.framework API is outdated')
@@ -2713,7 +2714,7 @@ config_host_data.set('CONFIG_RTNETLINK',
 config_host_data.set('CONFIG_SYSMACROS',
                      cc.has_header_symbol('sys/sysmacros.h', 'makedev'))
 config_host_data.set('HAVE_OPTRESET',
-                     cc.has_header_symbol('getopt.h', 'optreset'))
+                     cc.has_header_symbol('getopt.h', 'optreset', args: 
'-Wno-unused-value'))
 config_host_data.set('HAVE_IPPROTO_MPTCP',
                      cc.has_header_symbol('netinet/in.h', 'IPPROTO_MPTCP'))
 
@@ -2731,10 +2732,12 @@ config_host_data.set('HAVE_BLK_ZONE_REP_CAPACITY',
 # has_type
 config_host_data.set('CONFIG_IOVEC',
                      cc.has_type('struct iovec',
-                                 prefix: '#include <sys/uio.h>'))
+                                 prefix: '#include <sys/uio.h>',
+                                 args: '-Wno-unused-value'))
 config_host_data.set('HAVE_UTMPX',
                      cc.has_type('struct utmpx',
-                                 prefix: '#include <utmpx.h>'))
+                                 prefix: '#include <utmpx.h>',
+                                 args: '-Wno-unused-value'))
 
 config_host_data.set('CONFIG_EVENTFD', cc.links('''
   #include <sys/eventfd.h>
-- 
2.45.2