Re: [Qemu-devel] [PATCH, build fix] osdep: Work around MinGW assert

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 23/10/18 9:02, Richard Henderson wrote:
> In several places we use assert(FEATURE), and assume that if FEATURE
> is disabled, all following code is removed as unreachable.  Which allows
> us to compile-out functions that are only present with FEATURE, and
> have a link-time failure if the functions remain used.
> 
> MinGW does not mark its internal function _assert() as noreturn, so the
> compiler cannot see when code is unreachable, which leads to link errors
> for this host that are not present elsewhere.
> 
> The current build-time failure concerns 62823083b8a2, but I remember
> having seen this same error before.  Fix it once and for all for MinGW.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   include/qemu/osdep.h | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 4f8559e550..0c1e335a43 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -122,6 +122,18 @@ extern int daemon(int, int);
>   #include "glib-compat.h"
>   #include "qemu/typedefs.h"
>   
> +/*
> + * For mingw, as of v6.0.0, the function implementing the assert macro is
> + * not marked a noreturn, so the compiler cannot delete code following an
> + * assert(false) as unused.  We rely on this within the code base to delete
> + * code that is unreachable when features are disabled.
> + * All supported versions of Glib's g_assert() satisfy this requirement.
> + */
> +#ifdef __MINGW32__
> +#undef assert
> +#define assert(x)  g_assert(x)
> +#endif
> +
>   /*
>    * According to waitpid man page:
>    * WCOREDUMP
>