Date: Mon, 27 May 2013 16:21:52 +0200 From: Thomas Mueller <tmueller@sysgo.com> To: David Wolfskill <david@catwhisker.org> Cc: freebsd-ports@freebsd.org Subject: Re: Proper way to access executable's "environment"? Message-ID: <20130527162152.5c400069@tmu.ulm.sysgo.com> In-Reply-To: <20130526180629.GB1334@albert.catwhisker.org> References: <20130526172015.GA1334@albert.catwhisker.org> <51A24C77.6000108@gmx.net> <20130526180629.GB1334@albert.catwhisker.org>
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On Sun, 26 May 2013 11:06:29 -0700, David Wolfskill wrote: > On Sun, May 26, 2013 at 07:55:03PM +0200, Stefan Ehmann wrote: > > ... > > > So I have a couple of questions related to the above: > > > * Is the patch correct?... > > > > Should be fine. See environ(7) or > > http://pubs.opengroup.org/onlinepubs/9699919799/functions/environ.html: > > > > "In addition, the following variable, which must be declared by the user > > if it is to be used directly: extern char **environ; " > > Cool; thanks. > > (Aside: I'd be happy to hear of plausible reasons the earlier approach > does not appear to fail in i386. I'm suspecting some sort of > compatibilty shim -- which was jettisoned for amd64, probably quite > intentionally.) On AMD64 sizeof(void *)!=sizeof(int), thus warnings such as twm.c:250: warning: assignment makes pointer from integer without a cast should trigger alarms. ======= GDB session Program received signal SIGSEGV, Segmentation fault. 0x0000000801b60697 in strlen () from /lib/libc.so.7 (gdb) bt #0 0x0000000801b60697 in strlen () from /lib/libc.so.7 #1 0x000000000040b397 in main (argc=<value optimized out>, argv=<value optimized out>, environ=<value optimized out>) at twm.c:254 (gdb) frame 1 #1 0x000000000040b397 in main (argc=<value optimized out>, argv=<value optimized out>, environ=<value optimized out>) at twm.c:254 254 HomeLen = strlen(Home); (gdb) l 249 250 Home = getenv("HOME"); 251 if (Home == NULL) 252 Home = "./"; 253 254 HomeLen = strlen(Home); (gdb) p Home $1 = 0xffffffffffffdf3a <Error reading address 0xffffffffffffdf3a: Bad address> ========= Similarly, twm.c:306: warning: incompatible implicit declaration of built-in function 'calloc' including <stdlib.h> provides a proper declaration for calloc(). -- Thomas Mueller
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