vulkan: Add vk_asprintf and vk_vasprintf helpers

Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10318>

src/util/u_printf.cpp

@@ -22,6 +22,23 @@
 // Extract from Serge's printf clover code by airlied.
 
 #include "u_printf.h"
+#include <assert.h>
+#include <stdarg.h>
+#include "util/macros.h"
+
+/* Some versions of MinGW are missing _vscprintf's declaration, although they
+ * still provide the symbol in the import library. */
+#ifdef __MINGW32__
+_CRTIMP int _vscprintf(const char *format, va_list argptr);
+#endif
+
+#ifndef va_copy
+#ifdef __va_copy
+#define va_copy(dest, src) __va_copy((dest), (src))
+#else
+#define va_copy(dest, src) (dest) = (src)
+#endif
+#endif
 
 size_t util_printf_next_spec_pos(const std::string &s, size_t pos)
 {
@@ -51,3 +68,29 @@ size_t util_printf_next_spec_pos(const char *str, size_t pos)
 {
    return util_printf_next_spec_pos(std::string(str), pos);
 }
+
+size_t
+u_printf_length(const char *fmt, va_list untouched_args)
+{
+   int size;
+   char junk;
+
+   /* Make a copy of the va_list so the original caller can still use it */
+   va_list args;
+   va_copy(args, untouched_args);
+
+#ifdef _WIN32
+   /* We need to use _vcsprintf to calculate the size as vsnprintf returns -1
+    * if the number of characters to write is greater than count.
+    */
+   size = _vscprintf(fmt, args);
+   (void)junk;
+#else
+   size = vsnprintf(&junk, 1, fmt, args);
+#endif
+   assert(size >= 0);
+
+   va_end(args);
+
+   return size;
+}