Re: [PATCH] docs/style: allow C99 mixed declarations

[Stefan Hajnoczi]

On Mon, 5 Feb 2024 at 13:16, Samuel Tardieu <sam@rfc1149.net> wrote:
>
>
> Daniel P. Berrangé <berrange@redhat.com> writes:
>
> > $ gcc -Wall -Wuninitialized -o jump jump.c
>
> Note that many GCC warnings don't trigger if you don't enable
> optimizations. In the case you exhibit, adding -O is enough to get
> a sensible warning:
>
> $ gcc -Wall -O -o jump jump.c
> jump.c: In function ‘main’:
> jump.c:11:3: warning: ‘foo’ may be used uninitialized
> [-Wmaybe-uninitialized]
>    11 |   free(foo);
>       |   ^~~~~~~~~
> jump.c:8:9: note: ‘foo’ was declared here
>     8 |   char *foo = malloc(30);
>       |         ^~~

llvm also prints a warning:

  jump.c:5:7: warning: variable 'foo' is used uninitialized whenever
'if' condition is true [-Wsometimes-uninitialized]

I confirmed that QEMU's current compiler flags enable these warnings
so both gcc and llvm detect the issue that Daniel pointed out in QEMU
code.

Daniel: Does this address your concern about compiler warnings?


Stefan