Re: MS-Windows warnings (was build failure) for Emacs master

[Paul Eggert]

On 04/12/2016 01:54 PM, Angelo Graziosi wrote:

> current build logs have a lot of "garbage" like this:
>
> [...]
> C:/msys64/tmp/mingw-w64-emacs-git/src/emacs/lib-src/ntlib.c:110:15: 
> warning: format '%d' expects argument of type 'int', but argument 2 
> has type 'DWORD {aka long unsigned int}' [-Wformat=]
>
>        printf ("Checking parent status failed: %d\n", GetLastError ()); 

For portable code, that would be a valid warning. If GetLastError 
returns unsigned long, the format should use %lu, not %d

As I understand it, though, MS-Windows defines GetLastError to return 
unsigned int on 64-bit machines, and unsigned long on 32-bit machines 
(!). This idiosyncrasy could be handled in the MS-Windows port by 
something like this:

|#ifdef __MINGW64__ # define pDWORD "" #else # define pDWORD "l" #endif 
and then the above code could be: printf ("Checking parent status 
failed: %"pDWORD"u\n", GetLastError ()); |

Perhaps %u happens to work on both 32- and 64-bit MS-Windows, and if so 
then plain %u should suffice in practice.

> checking whether C compiler handles -Wbuiltin-macro-redefined... yes
> [...]
>
> Why enabling this by default? All this should be OFF by default and 
> only the maintainers which need it should enable it 

Warnings are enabled by default in master if you have a .git 
subdirectory (and thus are more likely to be a maintainer-type). See the 
thread containing this email:

http://lists.gnu.org/archive/html/emacs-devel/2016-04/msg00174.html

and the followup change here:

http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=5baecbc0ebc11178edd73431b644a5de0a31be25

It would be easy enough to disable -Wformat warnings when compiling 
anything under MS-Windows), if MS-Windows developers would prefer that. 
I'd rather leave these warnings enabled on non-MS-Windows platforms, 
though, as they're useful for catching portability glitches.