lib: record output positions in printfrr

This replaces `%n` with a safe, out-of-band option that simply records
the start and end offset of the output produced for each `%...`
specifier.

The old `%n` code is removed.

Signed-off-by: David Lamparter <equinox@diac24.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/printfrr.h b/lib/printfrr.h
index 549334ba5b..49243248d6 100644
--- a/lib/printfrr.h
+++ b/lib/printfrr.h
@@ -28,10 +28,17 @@
 extern "C" {
 #endif
 
+struct fmt_outpos {
+	unsigned int off_start, off_end;
+};
+
 struct fbuf {
 	char *buf;
 	char *pos;
 	size_t len;
+
+	struct fmt_outpos *outpos;
+	size_t outpos_n, outpos_i;
 };
 
 #define at(a, b) PRINTFRR(a, b)