PR #20330 opened by Marton Balint (cus)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20330
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20330.patch
And a minor factorization.
>From f8e83bce6269c95fbad90f34434ceb641bf753d5 Mon Sep 17 00:00:00 2001
From: Marton Balint <c...@passwd.hu>
Date: Sun, 24 Aug 2025 21:42:54 +0200
Subject: [PATCH 1/2] avutil/bprint: make av_bprintf use av_vbprintf
No reason to duplicate the code.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavutil/bprint.c | 33 +++++++++------------------------
1 file changed, 9 insertions(+), 24 deletions(-)
diff --git a/libavutil/bprint.c b/libavutil/bprint.c
index 4e9571715c..932c03ce50 100644
--- a/libavutil/bprint.c
+++ b/libavutil/bprint.c
@@ -96,35 +96,12 @@ void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer,
unsigned size)
*buf->str = 0;
}
-void av_bprintf(AVBPrint *buf, const char *fmt, ...)
-{
- unsigned room;
- char *dst;
- va_list vl;
- int extra_len;
-
- while (1) {
- room = av_bprint_room(buf);
- dst = room ? buf->str + buf->len : NULL;
- va_start(vl, fmt);
- extra_len = vsnprintf(dst, room, fmt, vl);
- va_end(vl);
- if (extra_len <= 0)
- return;
- if (extra_len < room)
- break;
- if (av_bprint_alloc(buf, extra_len))
- break;
- }
- av_bprint_grow(buf, extra_len);
-}
-
void av_vbprintf(AVBPrint *buf, const char *fmt, va_list vl_arg)
{
unsigned room;
char *dst;
- int extra_len;
va_list vl;
+ int extra_len;
while (1) {
room = av_bprint_room(buf);
@@ -142,6 +119,14 @@ void av_vbprintf(AVBPrint *buf, const char *fmt, va_list
vl_arg)
av_bprint_grow(buf, extra_len);
}
+void av_bprintf(AVBPrint *buf, const char *fmt, ...)
+{
+ va_list vl;
+ va_start(vl, fmt);
+ av_vbprintf(buf, fmt, vl);
+ va_end(vl);
+}
+
void av_bprint_chars(AVBPrint *buf, char c, unsigned n)
{
unsigned room, real_n;
--
2.49.1
>From 4532caf820dcb2bc2cbac3d4e782ad27cf9fd76b Mon Sep 17 00:00:00 2001
From: Marton Balint <c...@passwd.hu>
Date: Sun, 24 Aug 2025 21:35:41 +0200
Subject: [PATCH 2/2] avutil/bprint: fix av_bprint_strftime with %p format
string reporting truncated output
strftime returns 0 in case of an empty output (e.g. %p format string with some
locales), there is no way to distinguish this from a buffer-too-small error
condition. So we must use some heuristics to handle this case, and not consume
INT_MAX RAM and falsely report a truncated output.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavutil/bprint.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/libavutil/bprint.c b/libavutil/bprint.c
index 932c03ce50..fa244b2e04 100644
--- a/libavutil/bprint.c
+++ b/libavutil/bprint.c
@@ -167,6 +167,7 @@ void av_bprint_strftime(AVBPrint *buf, const char *fmt,
const struct tm *tm)
{
unsigned room;
size_t l;
+ size_t fmt_len = 0;
if (!*fmt)
return;
@@ -174,9 +175,16 @@ void av_bprint_strftime(AVBPrint *buf, const char *fmt,
const struct tm *tm)
room = av_bprint_room(buf);
if (room && (l = strftime(buf->str + buf->len, room, fmt, tm)))
break;
+
+ if (!fmt_len)
+ fmt_len = strlen(fmt);
+ /* A 256x space requirement for output is unlikely, so it is likely
empty */
+ if (room >> 8 > fmt_len)
+ break;
+
/* strftime does not tell us how much room it would need: let us
retry with twice as much until the buffer is large enough */
- room = !room ? strlen(fmt) + 1 :
+ room = !room ? fmt_len + 1 :
room <= INT_MAX / 2 ? room * 2 : INT_MAX;
if (av_bprint_alloc(buf, room)) {
/* impossible to grow, try to manage something useful anyway */
--
2.49.1
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