Defining _GNU_SOURCE hides the declaration of aligned_alloc

Yaakov Selkowitz
Wed Feb 3 03:15:00 GMT 2016

On 2016-02-02 16:27, Ken Brown wrote:
> The issue in the Subject line came up in connection with an emacs bug
> report.
> Here's a test case:
> $ gcc test.c -Wimplicit-function-declaration
> test.c: In function ‘main’:
> test.c:7:3: warning: implicit declaration of function ‘aligned_alloc’
> The cause is that the declaration of aligned_alloc in stdlib.h is
> guarded by #if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L; but
> defining _GNU_SOURCE causes __ISO_C_VISIBLE to be defined as 1999.
> Here's an excerpt from /usr/include/sys/cdefs.h showing how this happens:
> According to the discussion of the emacs bug I mentioned, Linux and
> FreeBSD don't have this issue.  Should Cygwin's headers be changed to
> conform to those other platforms?

Yes, it should.  I have added this to my queue of such fixes, which I 
hope to post soon.


Problem reports:
Unsubscribe info:

More information about the Cygwin mailing list