From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
Message-Id: <199807031713.TAA13344@sister.ludd.luth.se>
Subject: Re: Cross-compiling djlsr
To: djgpp-workers AT delorie DOT com (DJGPP-WORKERS)
Date: Fri, 3 Jul 1998 19:13:03 +0200 (MET DST)
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I looked at why Linux #defines _POSIX_C_SOURCE for you. On my system
(Debian 1.3.somthing, libc5-based) it's because of the "-D__linux__"
option that is passed as default to gcc as can be seen from "gcc -v
c.c":
 /usr/lib/gcc-lib/i486-linux/2.7.2.1/cpp -lang-c -v -undef
-D__GNUC__=2 -D__GNUC_MINOR__=7 -D__ELF__ -Dunix -Di386 -Dlinux
-D__ELF__ -D__unix__ -D__i386__ -D__linux__ -D__unix -D__i386
-D__linux -Asystem(unix) -Asystem(posix) -Acpu(i386) -Amachine(i386)
-D__i486__ c.c /tmp/cca06972.i
[...]


where c.c is as follows:
----- c.c starts. -----
#ifdef _POSIX_C_SOURCE
char pos1[] = "_POSIX_C_SOURCE defined";
#else
char pos1[] = "_POSIX_C_SOURCE not defined";
#endif

#include <stdio.h>
#ifdef _POSIX_C_SOURCE
char pos2[] = "_POSIX_C_SOURCE defined";
#else
char pos2[] = "_POSIX_C_SOURCE not defined";
#endif
----- c.c ends. -----

Examining c.s from "gcc -S c.c" yields:
pos1:
        .string "_POSIX_C_SOURCE not defined"
[...]
pos2:
        .string "_POSIX_C_SOURCE defined"


Trying with "gcc -U__linux__ -S c.c" yields:
pos1:
        .string "_POSIX_C_SOURCE not defined"
[...]
pos2:
        .string "_POSIX_C_SOURCE not defined"


So this is a work-around. Does anybody know if the flags above (like
the culprit "-D__linux__") really should really be defined if you
cross-compile?


Pettersson, Symphony No. 2,

							MartinS