[FFmpeg-devel] [PATCH 04/21] avformat: Redo cleanup of demuxer upon read_header() failure

[Andreas Rheinhardt]

If reading the header fails, the demuxer's read_close() function (if
existing) is not called automatically; instead several demuxers call it
via "goto fail" in read_header().

This commit intends to change this by adding a flag to AVInputFormat
that can be used to set on a per-AVInputFormat basis whether read_close()
should be called generically after an error during read_header().

The flag controlling this behaviour has been added because it might be
unsafe to call read_close() generally (e.g. this might lead to
read_close() being called twice and this might e.g. lead to double-frees
if av_free() instead of av_freep() is used; or a size field has not
been reset after freeing the elements (see the mov demuxer for an
example of this)). Yet the intention is to check and fix all demuxers
and make the flag redundant in the medium run.

The flag has been added to a new internal field of AVInputFormat,
flags_internal. When it has become redundant, it can be removed again
at the next major version bump.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavformat/avformat.h |  7 +++++++
 libavformat/utils.c    | 11 +++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 9b9b634ec3..50b90788b1 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -780,6 +780,13 @@ typedef struct AVInputFormat {
      * @see avdevice_capabilities_free() for more details.
      */
     int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
+
+#define FF_INPUTFORMAT_HEADER_CLEANUP 0x0001 /**< read_close() should be called
+                                                  on read_header() failure */
+    /**
+     * Can use flags: FF_INPUTFORMAT_HEADER_CLEANUP
+     */
+    int flags_internal;
 } AVInputFormat;
 /**
  * @}
diff --git a/libavformat/utils.c b/libavformat/utils.c
index a58e47fabc..87807a7841 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -400,8 +400,12 @@ int av_demuxer_open(AVFormatContext *ic) {
 
     if (ic->iformat->read_header) {
         err = ic->iformat->read_header(ic);
-        if (err < 0)
+        if (err < 0) {
+            if (ic->iformat->read_close &&
+                ic->iformat->flags_internal & FF_INPUTFORMAT_HEADER_CLEANUP)
+                ic->iformat->read_close(ic);
             return err;
+        }
     }
 
     if (ic->pb && !ic->internal->data_offset)
@@ -628,8 +632,11 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
 
     if (!(s->flags&AVFMT_FLAG_PRIV_OPT) && s->iformat->read_header)
-        if ((ret = s->iformat->read_header(s)) < 0)
+        if ((ret = s->iformat->read_header(s)) < 0) {
+            if (s->iformat->flags_internal & FF_INPUTFORMAT_HEADER_CLEANUP)
+                goto close;
             goto fail;
+        }
 
     if (!s->metadata) {
         s->metadata = s->internal->id3v2_meta;
-- 
2.20.1