Mail Archives: cygwin/2004/04/29/06:04:24
bertrand marquis wrote:
> Hi again,
>
> i just find the solution to my problem
> in fact it seems that adding:
>
> extern int optind;
> extern char *optarg;
>
> solve the problem. The compiler then auto-import these variables and it
> is working after. This problem doesn't seem to exist under linux but it
> could be a difference in versions between my linux and my cygwin.
>
> bertrand marquis a écrit:
>
>> Hi,
>>
>> I need to compile a program using libiberty.a and the function
>> getopt_long. When compiling with the flag -liberty my program crash
>> because it don't take the right arguments from the command line. But
>> without libiberty this part work before.
>>
>> i made a small program showing that problem, if anyone has an idea ?
>> i'm using the latest cygwin from the installer ,gcc-3.3.1 and ld
>> 2.15.90 20040312
>>
>> thanks
>>
>> You can find next my source code for the test program and the result i
>> have with it.
>>
>>
>> My test program:
>>
>> /*begin of argu.c*/
>> #include <unistd.h>
>> #include <getopt.h>
>> #include <ctype.h>
>> #include <stdio.h>
>>
>> int main(int argc, char **argv) {
>>
>> struct option long_opts[] = {
>> {"v", 1, 0, 'v'},
>> {"no-v", 0, 0, 'V'},
>> {"k", 1, 0, 'k'},
>> {"no-k", 0, 0, 'K'},
>> {"l", 1, 0, 'l'},
>> {"no-l", 0, 0, 'L'},
>> {0, 0, 0, 0}
>> };
>> int c;
>> while ((c = getopt_long(argc, argv, "v:Vk:Kl:L:",
>> long_opts, NULL)) != EOF) {
>>
>> switch(c) {
>> case 'v':
>> printf("v %s\n",optarg);
>> break;
>> case 'V':
>> printf("V\n");
>> break;
>> case 'k':
>> printf("k %s\n",optarg);
>> break;
>> case 'K':
>> printf("K\n");
>> break;
>> case 'l':
>> printf("l %s\n",optarg);
>> break;
>> case 'L':
>> printf("L\n");
>> break;
>> case '?':
>> printf("other:%c\n",c);
>> }
>> }
>> printf("argc=%d , optind=%d ,
>> file=%s\n",argc,optind,argc>optind?*(argv+optind):"none");
>> return 0;
>> }
>> /*end of argu.c*/
>>
>> when you compile it with : gcc argu.c -o argu.exe it works:
>> $ ./argu.exe -v abc -K test
>> v abc
>> K
>> argc=5 , optind=4 , file=test
>>
>> but when you compile it with gcc argu.c -o argu.exe -liberty it gives:
>> $ ./argu.exe -v abc -K test
>> v (null)
>> K
>> argc=5 , optind=1 , file=-v
When you link with libiberty you are linking to an implementation of getopt*
that does not correspond to the headers you have included.
There is no symbol called _optarg (or _optind, etc.) in libcygwin.a. The Cygwin
headers declare the opt* variables __declspec(dllimport). So when you include
the Cygwin headers, when you refer to optarg the symbol that gets generated is
__imp__optarg, which /is/ exported from libcygwin.a. The version of getopt* in
libiberty refers to symbols named _opt* and not __imp__opt*. So when you link
against libiberty, your program and getopt() are referring to different opt*
variables.
When you re-declare the opt* variables, you effectively undo the
__declspec(dllimport) so your program again refers to _opt* instead of
__imp__opt*. MSVC issues a warning in this case; gcc, it seems, does not.
A better way to solve this, I think, would be to link against libcygwin.a before
libiberty.a.
~$ gcc argu.c -o argu.exe -lcygwin -liberty
~$ ./argu.exe -v abc -K test
v abc
K
argc=5 , optind=4 , file=test
FWIW, this has come up before:
http://sources.redhat.com/ml/cygwin/2004-02/msg00063.html
HTH, Cheers
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