Re: [Qemu-block] [Qemu-devel] [PULL 00/32] Block layer patches

[Eric Blake]

On 07/11/2016 10:14 AM, Peter Maydell wrote:

> 
> Format string warning on OSX, I'm afraid:
> 
> /Users/pm215/src/qemu-for-merges/qemu-io-cmds.c:393:69: warning:
> format specifies type 'size_t' (aka 'unsigned long') but the argument
> has type 'unsigned long long' [-Wformat]
>             printf("Argument '%s' exceeds maximum size %zu\n", arg, SIZE_MAX);
>                                                        ~~~          ^~~~~~~~
>                                                        %llu
> /usr/include/stdint.h:153:20: note: expanded from macro 'SIZE_MAX'
> #define SIZE_MAX          UINT64_MAX
>                           ^~~~~~~~~~
> /usr/include/stdint.h:87:27: note: expanded from macro 'UINT64_MAX'
> #define UINT64_MAX        18446744073709551615ULL
>                           ^~~~~~~~~~~~~~~~~~~~~~~
> 
> This is a bug in the OSX system headers, but we need to work around
> it. This came up last year for some other format strings in the
> some source file, so the same fix should be ok here:
> https://patchwork.ozlabs.org/patch/542327/

Back then, our "fix" was a hack to add an explicit (uint64_t) cast at
the point of the printf, but that doesn't scale.  Wouldn't a better fix
be to osdep.h to add something along the lines of:

#if witness_for_buggy_header
#undef SIZE_MAX
#define SIZE_MAX working expression
#endif

so that it is fixed in one place for all uses?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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