vasprintf: rewrite. va_copy() was missing.

compat/vasprintf.c

@@ -25,13 +25,34 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <assert.h>
 
 int vasprintf (char **strp, const char *fmt, va_list ap)
 {
-    ssize_t len = vsnprintf (NULL, 0, fmt, ap) + 1;
-    char *res = malloc (len);
-    if (res == NULL)
-        return -1;
-    *strp = res;
-    return vsnprintf (res, len, fmt, ap);
+    va_list args;
+    int len;
+
+    va_copy (args, ap);
+    len = vsnprintf (NULL, 0, fmt, args);
+    va_end (args);
+
+    char *str = malloc (len + 1);
+    if (str != NULL)
+    {
+        int len2;
+
+        va_copy (args, ap);
+        len2 = vsprintf (str, fmt, args);
+        assert (len2 == len);
+        va_end (args);
+    }
+    else
+    {
+        len = -1;
+#ifndef NDEBUG
+        str = (void *)(intptr_t)0x41414141; /* poison */
+#endif
+    }
+    *strp = str;
+    return len;
 }