Re: There are still bugs in dirname(3) (glibc 2.2.3.pre1)

[Andreas Jaeger]

Uli, here's a patch for the test suite.  I don't have time to fix
dirname directly myself.

Thanks,
Andreas

2001-04-02  Andreas Jaeger  <address@hidden>

        * misc/tst-dirname.c (main): Add more tests, derived from a bug
        report by Michael Kerrisk <address@hidden>.

"Michael Kerrisk" <address@hidden> writes:

> Gidday,
> 
> A while back I submitted a patch for dirname(3) for glibc 2.2.1, which was 
> not correctly handling the case of trailing slashes in pathnames.  The 
> version is glibc 2.2.3pre1 is improved, but still broken.  SUSv2 says 
> 
>         "Trailing '/' character**s** in the path are not counted as 
>         part of the path"  
> 
> Note the plural!  (As usual for Unix pathnames, repeated slashes are 
> equivalent to a single slash).  Thus the 2.2.3pre1 version of dirname(3), 
> given the following paths:
> 
>        returns      Should return
> a//       a                .
> a////     a//              .
> ////a     ///              /
> //a//     //a              /
> 
> I resubmit my thoroughly tested (and now modified, since I discovered my 
> initial patch also broke on the last two cases) version below - with 
> perrmission to copyright to FSF and use and include in glibc under the 
> terms of GPL.
> 
> Cheers
> 
> Michael
> 
> 
> 
> char *
> dirname(char *path)
> {
>   static const char dot[] = ".";
>   char *last_slash;
> 
>   if (path == NULL || *path == '\0') {
>     /* NULL path or empty string: return "." */
>     path = (char *) dot;
>   } else {
>     last_slash = path + strlen(path) - 1;
> 
>     /* Ignore multiple slashes at end of path, step back until we find
>        a non-slash, or we reach start of string */
> 
>     while (*last_slash == '/' && last_slash > path)
>       --last_slash;
> 
>     if (*last_slash == '/')     /* We got to BOS and found no non-slash */
>       /* Pathname consisted only of slashes, return "/" */
> 
>       path[1] = '\0';
>     else {
>       /* Walk backwards to find slash */
>       while (*last_slash != '/' && last_slash > path)
>         last_slash --;
>       if (*last_slash == '/')           /* We found a slash */
>         if (last_slash == path)         /* But it was the first char */
>           path[1] = '\0';               /* So return "/" */
>         else {                          /* Slash is not first char, so... 
> */
> 
>           /* may have multiple slashes at end of directory spec,
>              so walk back till we reach a non-slash */
> 
>           while (*(last_slash-1) == '/' && last_slash > path)
>             last_slash --;
>           if (*last_slash  == '/')      /* We hit BOS */
>             *(last_slash+1) = '\0';     /* So make next char terminator */
>           else
>             *last_slash = '\0';         /* dirname ends here */
>         }
>       else
>         path = (char *) dot;            /* No slash found, return "." */
>     }
>   }
> 
>   return path;
> }
> 
> 
> 
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-- 
 Andreas Jaeger
  SuSE Labs address@hidden
   private address@hidden
    http://www.suse.de/~aj