From 64c5ad58d276d8a0463aa9ad2b34f75b7d1f4108 Mon Sep 17 00:00:00 2001
From: Jan Maria Matejka <mq@ucw.cz>
Date: Wed, 22 Aug 2018 14:58:53 +0200
Subject: [PATCH] Lib: recursive printf

Use like this:

void func(const char *msg, va_list args) {
  ...
  bvsnprintf(buf, len, "file %s, line %d: %V (foo %d, bar %d)", file, line, msg, &args, foo, bar);
  ...
}
---
 lib/printf.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/printf.c b/lib/printf.c
index 533a1300..cafeeb93 100644
--- a/lib/printf.c
+++ b/lib/printf.c
@@ -270,6 +270,17 @@ int bvsnprintf(char *buf, int size, const char *fmt, va_list args)
 				*str++ = ' ';
 			continue;
 
+		case 'V': {
+			const char *vfmt = va_arg(args, const char *);
+			va_list *vargs = va_arg(args, va_list *);
+			int res = bvsnprintf(str, size, vfmt, *vargs);
+			if (res < 0)
+				return -1;
+			str += res;
+			size -= res;
+			continue;
+			}
+
 		case 'p':
 			if (field_width == -1) {
 				field_width = 2*sizeof(void *);