[PATCH] meson: Avoid implicit declaration of functions

[PATCH] meson: Avoid implicit declaration of functions

[Michal Privoznik]

While detecting a presence of a function via 'cc.links()'
gives desired result (i.e. detects whether function is present),
it also produces a warning on systems where the function is not
present, e.g.:

  qemu.git/build/meson-private/tmph74x3p38/testfile.c:2:34: \
  warning: implicit declaration of function 'malloc_trim' [-Wimplicit-function-declaration]

We can check whether given function exists via
'cc.has_function()' firstly.

Resolves: https://bugs.gentoo.org/898810
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 meson.build | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/meson.build b/meson.build
index 2d48aa1e2e..5da4dbac24 100644
--- a/meson.build
+++ b/meson.build
@@ -1797,6 +1797,7 @@ malloc = []
 if get_option('malloc') == 'system'
   has_malloc_trim = \
     get_option('malloc_trim').allowed() and \
+    cc.has_function('malloc_trim', prefix: '#include <malloc.h>') and \
     cc.links('''#include <malloc.h>
                 int main(void) { malloc_trim(0); return 0; }''')
 else
@@ -1818,27 +1819,29 @@ gnu_source_prefix = '''
   #define _GNU_SOURCE
   #endif
 '''
-statx_test = gnu_source_prefix + '''
-  #include <sys/stat.h>
+statx_prefix = gnu_source_prefix + '''
+  #include<sys/stat.h>
+'''
+statx_test = statx_prefix + '''
   int main(void) {
     struct statx statxbuf;
     statx(0, "", 0, STATX_BASIC_STATS, &statxbuf);
     return 0;
   }'''
 
-has_statx = cc.links(statx_test)
+has_statx = cc.has_function('statx', prefix: statx_prefix) and \
+    cc.links(statx_test)
 
 # Check whether statx() provides mount ID information
 
-statx_mnt_id_test = gnu_source_prefix + '''
-  #include <sys/stat.h>
+statx_mnt_id_test = statx_prefix + '''
   int main(void) {
     struct statx statxbuf;
     statx(0, "", 0, STATX_BASIC_STATS | STATX_MNT_ID, &statxbuf);
     return statxbuf.stx_mnt_id;
   }'''
 
-has_statx_mnt_id = cc.links(statx_mnt_id_test)
+has_statx_mnt_id = has_statx and cc.links(statx_mnt_id_test)
 
 have_vhost_user_blk_server = get_option('vhost_user_blk_server') \
   .require(targetos == 'linux',
-- 
2.39.3

Re: [PATCH] meson: Avoid implicit declaration of functions

[Peter Maydell]

On Mon, 29 May 2023 at 08:58, Michal Privoznik <mprivozn@redhat.com> wrote:
>
> While detecting a presence of a function via 'cc.links()'
> gives desired result (i.e. detects whether function is present),
> it also produces a warning on systems where the function is not
> present, e.g.:
>
>   qemu.git/build/meson-private/tmph74x3p38/testfile.c:2:34: \
>   warning: implicit declaration of function 'malloc_trim' [-Wimplicit-function-declaration]

Produces a warning where ? On stdout/stderr ?

The linked bug report says "in the configure logs"
which is kinda vague. Warnings in the logfiles are
not a problem; warnings in the terminal output are...

> diff --git a/meson.build b/meson.build
> index 2d48aa1e2e..5da4dbac24 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1797,6 +1797,7 @@ malloc = []
>  if get_option('malloc') == 'system'
>    has_malloc_trim = \
>      get_option('malloc_trim').allowed() and \
> +    cc.has_function('malloc_trim', prefix: '#include <malloc.h>') and \
>      cc.links('''#include <malloc.h>
>                  int main(void) { malloc_trim(0); return 0; }''')
>  else

This seems super clunky -- surely this isn't the way Meson
intends people to write tests ?

thanks
-- PMM

Re: [PATCH] meson: Avoid implicit declaration of functions

[Paolo Bonzini]

On 5/29/23 12:24, Peter Maydell wrote:
> On Mon, 29 May 2023 at 08:58, Michal Privoznik <mprivozn@redhat.com> wrote:
>>
>> While detecting a presence of a function via 'cc.links()'
>> gives desired result (i.e. detects whether function is present),
>> it also produces a warning on systems where the function is not
>> present, e.g.:
>>
>>    qemu.git/build/meson-private/tmph74x3p38/testfile.c:2:34: \
>>    warning: implicit declaration of function 'malloc_trim' [-Wimplicit-function-declaration]
> 
> Produces a warning where ? On stdout/stderr ?
> 
> The linked bug report says "in the configure logs"
> which is kinda vague. Warnings in the logfiles are
> not a problem; warnings in the terminal output are...

It seems to be a lint:

  * QA Notice: Found the following implicit function declarations in configure logs:
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/tools-build/meson-logs/meson-log.txt:562 - malloc_trim
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/tools-build/meson-logs/meson-log.txt:591 - statx
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/tools-build/meson-logs/meson-log.txt:627 - statx
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/softmmu-build/meson-logs/meson-log.txt:718 - malloc_trim
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/softmmu-build/meson-logs/meson-log.txt:747 - statx
  *   /var/tmp/portage/app-emulation/qemu-7.2.0-r3/work/qemu-7.2.0/softmmu-build/meson-logs/meson-log.txt:783 - statx
  * Check that no features were accidentally disabled.
  * See https://wiki.gentoo.org/wiki/Modern_C_porting.

So, not an actual bug but more of a favor that we can do to the distros.

>> +    cc.has_function('malloc_trim', prefix: '#include <malloc.h>') and \
>>       cc.links('''#include <malloc.h>
>>                   int main(void) { malloc_trim(0); return 0; }''')
> 
> This seems super clunky -- surely this isn't the way Meson
> intends people to write tests ?

For this one can remove the cc.links test altogether, so this part of the
patch is okay.

The statx is less clear.

> 
> +statx_test = statx_prefix + '''
>    int main(void) {
>      struct statx statxbuf;
>      statx(0, "", 0, STATX_BASIC_STATS, &statxbuf);
>      return 0;
>    }'''
>  
> -has_statx = cc.links(statx_test)
> +has_statx = cc.has_function('statx', prefix: statx_prefix) and \
> +    cc.links(statx_test) 

Here we could replace cc.links with a cc.has_header_symbol('sys/stat.h',
'STATX_BASIC_STATS'), and likewise for has_statx_mnt_id below.

If it was just has_statx I would rather leave things as is.  However,
given that there is has_statx_mnt_id too, I'd apply a v2 that removes
usage of cc.links for these three tests.

Paolo

Re: [PATCH] meson: Avoid implicit declaration of functions

[Michael Tokarev]

29.05.2023 10:56, Michal Privoznik пишет:
> While detecting a presence of a function via 'cc.links()'
> gives desired result (i.e. detects whether function is present),
> it also produces a warning on systems where the function is not
> present, e.g.:
> 
>    qemu.git/build/meson-private/tmph74x3p38/testfile.c:2:34: \
>    warning: implicit declaration of function 'malloc_trim' [-Wimplicit-function-declaration]
> 
> We can check whether given function exists via
> 'cc.has_function()' firstly.

This just slows down the configure step, it looks like.
Shouldn't we use cc.has_function() *instead* of our cc.links(),
but not both?

/mjt