Re: [PATCH 1/2] Add QEMU_WARN_UNUSED_RESULT attribute

[Philippe Mathieu-Daudé]

On 10/11/23 10:16, Manos Pitsidianakis wrote:
> This commit adds QEMU_WARN_UNUSED_RESULT, a macro for the gcc function
> attribute `warn_unused_result`. The utility of this attribute is to
> ensure functions that return values that need to be inspected are not
> ignored by the caller.
>
> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
>   include/qemu/compiler.h | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)

> +/*
> + * From GCC documentation:
> + *
> + *   The warn_unused_result attribute causes a warning to be emitted if a
> + *   caller of the function with this attribute does not use its return value.
> + *   This is useful for functions where not checking the result is either a
> + *   security problem or always a bug, such as realloc.
> + */
> +#if __has_attribute(warn_unused_result)
> +# define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
> +#else
> +# define QEMU_WARN_UNUSED_RESULT
> +#endif

FWIW I sometimes use:

+#if __has_attribute(nonnull)
+# define QEMU_NONNULL(indexes...) __attribute__((nonnull((indexes))))
+#else
+# define QEMU_NONNULL(indexes...)
+#endif

when doing tree-wide refactors, then remove the attribute because
prototypes become really ugly.