(snprintf): memcpy LEN bytes, not SIZE - 1, when

LEN is smaller than SIZE.  Suggested by Bruno Haible.
Also, help the compiler to keep LEN in a register.

2 files changed, 11 insertions, 3 deletions

diff --git a/lib/ChangeLog b/lib/ChangeLog
index 7f0ed7435..802bde813 100644
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,9 @@
+2006-08-11  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* snprintf.c (snprintf): memcpy LEN bytes, not SIZE - 1, when
+	LEN is smaller than SIZE.  Suggested by Bruno Haible.
+	Also, help the compiler to keep LEN in a register.
+
 2006-08-10  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Import the following changes from libc:
diff --git a/lib/snprintf.c b/lib/snprintf.c
index c281f7c58..ef00f55b4 100644
--- a/lib/snprintf.c
+++ b/lib/snprintf.c
@@ -45,11 +45,12 @@ snprintf (char *str, size_t size, const char *format, ...)
 {
   char *output;
   size_t len;
+  size_t lenbuf = size;
   va_list args;
 
   va_start (args, format);
-  len = size;
   output = vasnprintf (str, &len, format, args);
+  len = lenbuf;
   va_end (args);
 
   if (!output)
@@ -59,8 +60,9 @@ snprintf (char *str, size_t size, const char *format, ...)
     {
       if (size)
 	{
-	  memcpy (str, output, size - 1);
-	  str[size - 1] = '\0';
+	  size_t pruned_len = (len < size ? len : size - 1);
+	  memcpy (str, output, pruned_len);
+	  str[pruned_len] = '\0';
 	}
 
       free (output);