[Bug-gnulib] vasnprintf.c: patch for inadequate snprintf on HPUX 10.20

[Jim Meyering]

Hi Bruno,

This started because people reported that `who' of coreutils-5.0.91
would fail with an apparent out of memory error on HPUX systems.
It came down to the fact that asprintf would sometimes return -1
(with errno == EINVAL) under some circumstances.
That in turn was because vasnprintf didn't handle the case in which
snprintf doesn't honor %n, and in addition returns -1 when formatting
the supplied arguments would require more than the specified size.

Here's the proposed patch:

2003-10-19  Jim Meyering  <address@hidden>

        * vasnprintf.c (vasnprintf): Work around losing snprintf on
        e.g. HPUX 10.20.


Index: vasnprintf.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/vasnprintf.c,v
retrieving revision 1.7
diff -u -p -u -p -r1.7 vasnprintf.c
--- vasnprintf.c        13 Sep 2003 22:14:47 -0000      1.7
+++ vasnprintf.c        19 Oct 2003 19:04:35 -0000
@@ -707,6 +707,22 @@ vasnprintf (char *resultbuf, size_t *len
                            p[1] = '\0';
                            continue;
                          }
+                       else if (retcount < 0)
+                         {
+                           /* The system's snprintf is sorely deficient:
+                              it doesn't recognize the `%n' directive, and it
+                              returns -1 (rather than the length that would
+                              have been required) when the buffer is too small.
+                              This is the case at with least HPUX 10.20.
+                              Double the memory allocation.  */
+                           size_t n = allocated;
+                           if (n < 2 * allocated)
+                             {
+                               n = 2 * allocated;
+                               ENSURE_ALLOCATION (n);
+                               continue;
+                             }
+                         }
                        count = retcount;
                      }
 #endif