[PATCH][PR gdb/24351] Fix wrong format specification in display_selector()

[Simon Marchi]

On 2019-03-28 11:46, Jon Turney wrote:
> On 17/03/2019 18:44, Simon Marchi wrote:
>> On 2019-03-17 05:48, Владимир Мартьянов wrote:
>>> There are a wrong format strings in function display_selector() in
>>> file windows-nat.c. This leads to build error using Cygwin on 
>>> Windows.
>>> LDT_ENTRY.HighWord is a DWORD, which is unsigned long int, so the
>>> format specification should be for long int, not simply int.
>>> 
>>> gdb/ChangeLog:
>>> 2019-03-17  Vladimir Martyanov  <vilgeforce@gmail.com>
>>> 
>>> Â Â Â  PR gdb/24351
>>> Â Â Â  * windows-nat.c (display_selector): Format specifications fixed
>>> 
>>> Patch and changelog files are attached
>> 
>> Thanks, this LGTM.  I altavista'ed and it looks like this is the right 
>> thing to do to print DWORDs.  It also builds fine with 
>> i686-w64-mingw32-gcc and x86_64-w64-mingw32-gcc on Linux.
> 
> Thanks for looking at this.  But did you test this with
> x86_64-pc-cygwin?  It fails to build for me:
> 
>> ../../gdb/windows-nat.c: In function ‘int display_selector(HANDLE, 
>> DWORD)’:
>> ../../gdb/windows-nat.c:1099:65: error: format ‘%lx’ expects argument 
>> of type ‘long unsigned int’, but argument 2 has type ‘unsigned int’ 
>> [-Werror=format=]
>>     printf_filtered ("Unknown type 0x%lx",info.HighWord.Bits.Type);
>>                                           ~~~~~~~~~~~~~~~~~~~~~~~^
>> ../../gdb/windows-nat.c:1106:74: error: format ‘%ld’ expects argument 
>> of type ‘long int’, but argument 2 has type ‘unsigned int’ 
>> [-Werror=format=]
>>        printf_filtered ("Priviledge level = %ld. ", 
>> info.HighWord.Bits.Dpl);
> 
> I believe this is because, unfortunately, DWORD is not long on 64-bit
> Cygwin, because that is LP64 (See [1]).
> 
> I think the only portable way to write this (short of introducing
> inttypes.h PRI_-style macros) is to explicitly cast DWORD type values
> to unsigned long or unsigned int, and use the appropriate format (e.g.
> see [2] for a similar patch I wrote for xserver)
> 
> Patch attached.
> 
> [1] https://cygwin.com/faq.html#faq.programming.64bitporting
> [2]
> https://cgit.freedesktop.org/xorg/xserver/commit/?id=aa83c61f510121da20b56e8f7de700193f7d16b5

Thanks for the patch, I pushed it.

Simon