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On Feb 17 18:24, Jon TURNEY wrote: > > Consider the following: > > $ cat test.c > #include <string.h> > #include <stdlib.h> > > int main() > { > long long i = random(); > return ffsll(i); > } > > ffsll() is a GNU extension and should be prototyped when _GNU_SOURCE is > defined. > > random() is in SUSv2 and requires _XOPEN_SOURCE=500 > > $ gcc test.c -Wall -ansi -D_XOPEN_SOURCE=700 > test.c: In function âmainâ: > test.c:8:2: warning: implicit declaration of function âffsllâ > > This is correct > > $ gcc test.c -Wall -ansi -D_XOPEN_SOURCE=700 -D_GNU_SOURCE > test.c: In function âmainâ: > test.c:8:2: warning: implicit declaration of function âffsllâ > > This looks like a problem with newlib's sys/cdefs.h. _XOPEN_SOURCE causes > _POSIX_C_SOURCE to be defined, which prevents _GNU_SOURCE from being > considered. > > $ gcc test.c -Wall -ansi -D_GNU_SOURCE > test.c: In function âmainâ: > test.c:7:2: warning: implicit declaration of function ârandomâ > > _GNU_SOURCE is supposed to imply some value of _XOPEN_SOURCE, but only > actually turns on __XSI_VISIBLE. > > The patch I wrote for cygwin's stdlib.h [1] explicitly checks _XOPEN_SOURCE. > Should this be a check for XSI_VISIBLE? or should cdefs.h also define > _XOPEN_SOURCE (and all the other feature test macros that _GNU_SOURCE is > defined to be equivalent to)? The check should be one for XSI_VISIBLE. I'm not sure about cdefs.h, though. Maybe you want to ask the question on the newlib ML? I'll look into it tomorrow. Thanks, Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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