Re: libiberty and getopt

[David Fritz]

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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