Re: strerror_r-posix on MSVC

[Bruno Haible]

> 2011-09-22  Bruno Haible  <address@hidden>
> 
>       strerror_r-posix: Avoid a link error on MSVC.
>       * m4/strerror_r.m4 (gl_PREREQ_STRERROR_R): Check for snprintf.
>       * lib/strerror_r.c (snprintf): Define to _snprintf if it doesn't exist.

Oops, that fixed the link error, but at the cost of a test suite failure:

  test-strerror_r.c:119: assertion failed
  FAIL: test-strerror_r.exe

The Microsoft _snprintf() function not only has a different return value
convention than ISO C snprintf(), it also does not NUL-terminate the result!

Workaround:


2011-09-25  Bruno Haible  <address@hidden>

        strerror_r-posix: Fix for MSVC 9.
        * lib/strerror_r.c (local_snprintf): New function.
        (snprintf): Define to local_snprintf, not to _snprintf.

--- lib/strerror_r.c.orig       Sun Sep 25 14:50:08 2011
+++ lib/strerror_r.c    Sun Sep 25 14:49:15 2011
@@ -87,9 +87,24 @@
 #endif
 
 /* On MSVC, there is no snprintf() function, just a _snprintf().
-   It is of lower quality, but sufficient for the simple use here.  */
+   It is of lower quality, but sufficient for the simple use here.
+   We only have to make sure to NUL terminate the result (_snprintf
+   does not NUL terminate, like strncpy).  */
 #if !HAVE_SNPRINTF
-# define snprintf _snprintf
+static int
+local_snprintf (char *buf, size_t buflen, const char *format, ...)
+{
+  va_list args;
+  int result;
+  
+  va_start (args, format);
+  result = _vsnprintf (buf, buflen, format, args);
+  va_end (args);
+  if (buflen > 0 && (result < 0 || result >= buflen))
+    buf[buflen - 1] = '\0';
+  return result;
+}
+# define snprintf local_snprintf
 #endif
 
 /* Copy as much of MSG into BUF as possible, without corrupting errno.

-- 
In memoriam Safia Ahmed-jan <http://en.wikipedia.org/wiki/Safia_Ahmed-jan>