Fix obstack_printf() (slightly broken in r27474).

[libfirm] / ir / obstack / obstack_printf.c

diff --git a/ir/obstack/obstack_printf.c b/ir/obstack/obstack_printf.c
index 1b432e2..ab494bb 100644 (file)
--- a/ir/obstack/obstack_printf.c
+++ b/ir/obstack/obstack_printf.c
@@ -9,42 +9,40 @@
 
 int obstack_printf(struct obstack *obst, const char *fmt, ...)
 {
-       char  buf[128];
-       char *buffer = buf;
+       char    buf[128];
+       char   *buffer = buf;
+       size_t  size   = lengthof(buf);
        va_list ap;
-       int len;
+       int     len;
 
-       va_start(ap, fmt);
-       len = vsnprintf(buffer, sizeof(buffer), fmt, ap);
-       va_end(ap);
-       if (len < 0 || len >= (int) sizeof(buffer)) {
-               size_t size   = len >= 0 ? (size_t) len : sizeof(buffer) * 2;
-               char  *buffer = malloc(size);
-               do {
-                       if (buffer == NULL)
-                               return -1;
-
-                       va_start(ap, fmt);
-                       len = vsnprintf(buffer, size, fmt, ap);
-                       va_end(ap);
+       for (;;) {
+               va_start(ap, fmt);
+               len = vsnprintf(buffer, sizeof(buffer), fmt, ap);
+               va_end(ap);
 
-                       /* snprintf should return -1 only in the error case, but older
-                        * glibcs and probably other systems are buggy in this respect and
-                        * return -1 if the buffer was too small. We only abort for LARGE
-                        * unrealistic buffer sizes here */
-                       if (len < 0) {
-                               if (size > 65536)
-                                       return -1;
-                               size *= 2;
-                               buffer = realloc(buffer, size);
-                       } else if (len >= (int) size) {
-                               /* this should not happen if snprintf works correctly */
-                               abort();
-                       }
-               } while (len < 0);
-               free(buffer);
+               /* snprintf should return -1 only in the error case, but older glibcs
+                * and probably other systems are buggy in this respect and return -1 if
+                * the buffer was too small. We only abort for LARGE unrealistic buffer
+                * sizes here */
+               if (len < 0) {
+                       if (buffer != buf)
+                               free(buffer);
+                       if (size > 65536)
+                               return -1;
+                       size *= 2;
+               } else if ((size_t)len >= size) {
+                       /* If we come here more than once, vsnprintf() returned garbage */
+                       assert(buffer == buf);
+                       size = (size_t)len + 1;
+               } else {
+                       break;
+               }
+               buffer = malloc(buffer, size);
        }
+
        obstack_grow(obst, buffer, len);
+       if (buffer != buf)
+               free(buffer);
 
        return len;
 }