qemu: Don't initialize struct utsname

[libvirt] [PATCH] qemu: Don't initialize struct utsname

Posted by Jiri Denemark 7 years, 9 months ago

It breaks the build and it is not really useful for anything.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---

Pushed under the build breaker rule.

 src/qemu/qemu_capabilities.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 2c573827f1..5e03447baa 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -5431,7 +5431,7 @@ virQEMUCapsCacheNew(const char *libDir,
     char *capsCacheDir = NULL;
     virFileCachePtr cache = NULL;
     virQEMUCapsCachePrivPtr priv = NULL;
-    struct utsname uts = { 0 };
+    struct utsname uts;
 
     if (virAsprintf(&capsCacheDir, "%s/capabilities", cacheDir) < 0)
         goto error;
-- 
2.16.0

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Re: [libvirt] [PATCH] qemu: Don't initialize struct utsname

Posted by Daniel P. Berrange 7 years, 9 months ago

On Mon, Jan 22, 2018 at 02:54:42PM +0100, Jiri Denemark wrote:
> It breaks the build and it is not really useful for anything.

Why does that break the build ?   "{ 0 }" is a valid initializer for
any struct according to the C standards.

> 
> Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
> ---
> 
> Pushed under the build breaker rule.
> 
>  src/qemu/qemu_capabilities.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index 2c573827f1..5e03447baa 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -5431,7 +5431,7 @@ virQEMUCapsCacheNew(const char *libDir,
>      char *capsCacheDir = NULL;
>      virFileCachePtr cache = NULL;
>      virQEMUCapsCachePrivPtr priv = NULL;
> -    struct utsname uts = { 0 };
> +    struct utsname uts;
>  
>      if (virAsprintf(&capsCacheDir, "%s/capabilities", cacheDir) < 0)
>          goto error;
> -- 
> 2.16.0
> 
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Regards,
Daniel
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Re: [libvirt] [PATCH] qemu: Don't initialize struct utsname

Posted by Jiri Denemark 7 years, 9 months ago

On Mon, Jan 22, 2018 at 14:01:26 +0000, Daniel P. Berrange wrote:
> On Mon, Jan 22, 2018 at 02:54:42PM +0100, Jiri Denemark wrote:
> > It breaks the build and it is not really useful for anything.
> 
> Why does that break the build ?   "{ 0 }" is a valid initializer for
> any struct according to the C standards.

Yeah, it seems -Wmissing-braces falsely reports missing braces in there.
It worked just fine on my host, by our Jenkins builders all failed on
it. Anyway, I didn't bother looking at details as it's easier to drop
the initializer. And doing so makes usage of struct utsname in libvirt
consistent.

Jirka

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Re: [libvirt] [PATCH] qemu: Don't initialize struct utsname

Posted by Daniel P. Berrange 7 years, 9 months ago

On Mon, Jan 22, 2018 at 03:12:46PM +0100, Jiri Denemark wrote:
> On Mon, Jan 22, 2018 at 14:01:26 +0000, Daniel P. Berrange wrote:
> > On Mon, Jan 22, 2018 at 02:54:42PM +0100, Jiri Denemark wrote:
> > > It breaks the build and it is not really useful for anything.
> > 
> > Why does that break the build ?   "{ 0 }" is a valid initializer for
> > any struct according to the C standards.
> 
> Yeah, it seems -Wmissing-braces falsely reports missing braces in there.
> It worked just fine on my host, by our Jenkins builders all failed on
> it. Anyway, I didn't bother looking at details as it's easier to drop
> the initializer. And doing so makes usage of struct utsname in libvirt
> consistent.

Looks like it generates the bogus warning when the first field of the
struct is itself another struct.

eg

  struct Base {
     int a;
  }

  struct One {
     int b;
     struct base c;
  };

  struct Two {
     struct base c;
     int b;
  };


  struct One one = {0};
  struct Two two = {0};


The 'two' initializer generates a warning but the 'one' initializer
does not. So that explains why most of our {0} initalizers are working
ok at least.

Regards,
Daniel
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