Rework duk_push_vsprintf() loop to reduce code size

src/duk_api.c

@@ -2579,7 +2579,7 @@ const char *duk_push_vsprintf(duk_context *ctx, const char *fmt, va_list ap) {
 	duk_uint8_t stack_buf[DUK_PUSH_SPRINTF_INITIAL_SIZE];
 	size_t sz = DUK_PUSH_SPRINTF_INITIAL_SIZE;
 	int pushed_buf = 0;
-	void *buf = (void *) stack_buf;
+	void *buf;
 	int len;
 	const char *res;
 
@@ -2599,10 +2599,6 @@ const char *duk_push_vsprintf(duk_context *ctx, const char *fmt, va_list ap) {
 		sz = DUK_PUSH_SPRINTF_INITIAL_SIZE;
 	}
 	DUK_ASSERT(sz > 0);
-	if (sz > sizeof(stack_buf)) {
-		pushed_buf = 1;
-		buf = duk_push_dynamic_buffer(ctx, sz);
-	}
 
 	/* Try to make do with a stack buffer to avoid allocating a temporary buffer.
 	 * This works 99% of the time which is quite nice.
@@ -2610,6 +2606,16 @@ const char *duk_push_vsprintf(duk_context *ctx, const char *fmt, va_list ap) {
 	for (;;) {
 		va_list ap_copy;  /* copied so that 'ap' can be reused */
 
+		if (sz <= sizeof(stack_buf)) {
+			buf = stack_buf;
+		} else if (!pushed_buf) {
+			pushed_buf = 1;
+			buf = duk_push_dynamic_buffer(ctx, sz);
+		} else {
+			buf = duk_resize_buffer(ctx, -1, sz);
+		}
+		DUK_ASSERT(buf != NULL);
+
 		DUK_VA_COPY(ap_copy, ap);
 		len = duk__try_push_vsprintf(ctx, buf, sz, fmt, ap_copy);
 		va_end(ap_copy);
@@ -2622,14 +2628,6 @@ const char *duk_push_vsprintf(duk_context *ctx, const char *fmt, va_list ap) {
 		if (sz >= DUK_PUSH_SPRINTF_SANITY_LIMIT) {
 			DUK_ERROR(thr, DUK_ERR_API_ERROR, "cannot sprintf, required buffer insanely long");
 		}
-
-		if (!pushed_buf) {
-			pushed_buf = 1;
-			buf = duk_push_dynamic_buffer(ctx, sz);
-		} else {
-			buf = duk_resize_buffer(ctx, -1, sz);
-		}
-		DUK_ASSERT(buf != NULL);
 	}
 
 	/* Cannot use duk_to_string() on the buffer because it is usually