Make rpmExpand() smarter wrt memory allocations

- precalculate unexpanded size and allocate enough for that plus MACROBUFSIZ
  for expansion
- typical allocation is way smaller than what gets allocated "just in case",
  calculate expanded size and realloc to actual size to avoid wasting
  memory

1 files changed, 12 insertions, 1 deletions

diff --git a/rpmio/macro.c b/rpmio/macro.c
index 198056f3b..ad1f94a44 100644
--- a/rpmio/macro.c
+++ b/rpmio/macro.c
@@ -1583,15 +1583,26 @@ rpmExpand(const char *arg, ...)
 	goto exit;
     }
 
-    buf = xmalloc(blen);
+    /* precalculate unexpanded size on top of MACROBUFSIZ */
+    va_start(ap, arg);
+    for (s = arg; s != NULL; s = va_arg(ap, const char *))
+	blen += strlen(s);
+    va_end(ap);
+
+    buf = xmalloc(blen + 1);
     buf[0] = '\0';
 
     va_start(ap, arg);
     for (pe = buf, s = arg; s != NULL; s = va_arg(ap, const char *))
 	pe = stpcpy(pe, s);
     va_end(ap);
+
     (void) expandMacros(NULL, NULL, buf, blen);
 
+    /* expanded output is usually much less than alloced buffer, downsize */
+    blen = strlen(buf);
+    buf = xrealloc(buf, blen + 1);
+
 exit:
     return buf;
 }