bug in cygwin's gcc/g++ getopt_long(): erroneous "ambiguous option"

["Dan Tsafrir" <dan dot tsafrir at gmail dot com>]

Hi,

When given certain long options, Cygwin's getopt_long() function
erroneously fails on "ambiguous option". The short program below
illustrates the problem: getopt_long() wrongfully reports the "--xy"
option as ambiguous.

Strangely, if flipping the order of the 2nd and 3rd entries in the
options-array (by compiling the program with -DNO_BUG) the bug goes
away, clearly demonstrating inconsistent Cygwin/getopt_long behavior.

The bug is triggered when compiling the program with Cygwin's default
gcc/g++ (3.4.4) or with gcc-4/g++-4 (4.3.2). The bug does not occur
when compiling the program with gcc/g++ (ver 3 or 4) on other OSes
(e.g., Linux).

A fix would be appreciated.
Best,
    --Dan

// start program:

#include <stdio.h>
#include <getopt.h>

const struct option lopts[] = {
#ifdef NO_BUG
    {"xy1" , required_argument, NULL, 'a' },
    {"xy"  , required_argument, NULL, 'b' },
    {"xy2" , required_argument, NULL, 'c' },
    {NULL  , 0                , NULL,  0  },
#else /* swapping order of 2nd and 3rd entries generates the bug */
    {"xy1" , required_argument, NULL, 'a' },
    {"xy2" , required_argument, NULL, 'c' },
    {"xy"  , required_argument, NULL, 'b' },
    {NULL  , 0                , NULL,  0  },
#endif
};

int main()
{
    const char* argv[] = {"./a", "--xy=1", NULL};
    int argc = 2;
    int index, c;

    // if NO_BUG defined, will print: "got opt=b" [OK]
    // otherwise: "a: ambiguous option -- xy" [BUG]
    if( (c = getopt_long(argc, (char**)argv, "A:B:C", lopts, &index)) != EOF )
        printf("got opt=%c\n", c);

    return 0;
}

// end program

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