vasprintf_compat.h: spin-off this compat header ; use math_compat.h as template

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

vasprintf_compat.h

@@ -0,0 +1,45 @@
+#ifndef __vasprintf_compat_h
+#define __vasprintf_compat_h
+
+#if !defined(HAVE_VSNPRINTF) && defined(_MSC_VER)
+# define vsnprintf _vsnprintf
+#elif !defined(HAVE_VSNPRINTF) /* !HAVE_VSNPRINTF */
+# error Need vsnprintf!
+#endif /* !HAVE_VSNPRINTF && defined(WIN32) */
+
+#if !defined(HAVE_VASPRINTF)
+/* CAW: compliant version of vasprintf */
+static int vasprintf(char **buf, const char *fmt, va_list ap)
+{
+#ifndef WIN32
+	static char _T_emptybuffer = '\0';
+#endif /* !defined(WIN32) */
+	int chars;
+	char *b;
+
+	if(!buf) { return -1; }
+
+#ifdef WIN32
+	chars = _vscprintf(fmt, ap)+1;
+#else /* !defined(WIN32) */
+	/* CAW: RAWR! We have to hope to god here that vsnprintf doesn't overwrite
+	   our buffer like on some 64bit sun systems.... but hey, its time to move on */
+	chars = vsnprintf(&_T_emptybuffer, 0, fmt, ap)+1;
+	if(chars < 0) { chars *= -1; } /* CAW: old glibc versions have this problem */
+#endif /* defined(WIN32) */
+
+	b = (char*)malloc(sizeof(char)*chars);
+	if(!b) { return -1; }
+
+	if((chars = vsprintf(b, fmt, ap)) < 0)
+	{
+		free(b);
+	} else {
+		*buf = b;
+	}
+
+	return chars;
+}
+#endif /* !HAVE_VASPRINTF */
+
+#endif /* __vasprintf_compat_h */