Re: [libav-devel] [PATCH] avpacket: Initialize the allocated padding area in side data

[Luca Barbato]

On 01/02/2018 14:02, Martin Storsjö wrote:

This makes sure that consumers of the side data actually can
rely on the padding as intended, without having the callers of
av_packet_new_side_data to explicitly zero initialize it.
---
  libavcodec/avpacket.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 93e9eb6ae7..c705df3d59 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -271,6 +271,7 @@ uint8_t *av_packet_new_side_data(AVPacket *pkt, enum 
AVPacketSideDataType type,
  data = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
  if (!data)
  return NULL;
+memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
  ret = av_packet_add_side_data(pkt, type, data, size);

  if (ret < 0) {



Fine for me.
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Re: [libav-devel] [PATCH] avpacket: Initialize the allocated padding area in side data

[Martin Storsjö]

On Thu, 1 Feb 2018, wm4 wrote:


On Thu,  1 Feb 2018 15:02:37 +0200
Martin Storsjö  wrote:


This makes sure that consumers of the side data actually can
rely on the padding as intended, without having the callers of
av_packet_new_side_data to explicitly zero initialize it.
---
 libavcodec/avpacket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 93e9eb6ae7..c705df3d59 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -271,6 +271,7 @@ uint8_t *av_packet_new_side_data(AVPacket *pkt, enum 
AVPacketSideDataType type,
 data = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
 if (!data)
 return NULL;
+memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);

 ret = av_packet_add_side_data(pkt, type, data, size);
 if (ret < 0) {


+1, though I also have trouble believing that just clearing the entire
thing (including side data contents) would cause any kind of performance
trouble. (I.e. using av_mallocz.)


Yes, that'd probably also be just as nice. The upside with this approach 
is that tools more easily can point out if you as a caller forgot to 
initialize the data you actually asked to have allocated for you, but I 
don't have a very strong opinion either way.


// Martin
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Re: [libav-devel] [PATCH] avpacket: Initialize the allocated padding area in side data

[wm4]

On Thu,  1 Feb 2018 15:02:37 +0200
Martin Storsjö  wrote:

> This makes sure that consumers of the side data actually can
> rely on the padding as intended, without having the callers of
> av_packet_new_side_data to explicitly zero initialize it.
> ---
>  libavcodec/avpacket.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
> index 93e9eb6ae7..c705df3d59 100644
> --- a/libavcodec/avpacket.c
> +++ b/libavcodec/avpacket.c
> @@ -271,6 +271,7 @@ uint8_t *av_packet_new_side_data(AVPacket *pkt, enum 
> AVPacketSideDataType type,
>  data = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
>  if (!data)
>  return NULL;
> +memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
>  
>  ret = av_packet_add_side_data(pkt, type, data, size);
>  if (ret < 0) {

+1, though I also have trouble believing that just clearing the entire
thing (including side data contents) would cause any kind of performance
trouble. (I.e. using av_mallocz.)

(Disregard my other empty reply I possibly sent, not sure.)
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[libav-devel] [PATCH] avpacket: Initialize the allocated padding area in side data

[Martin Storsjö]

This makes sure that consumers of the side data actually can
rely on the padding as intended, without having the callers of
av_packet_new_side_data to explicitly zero initialize it.
---
 libavcodec/avpacket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 93e9eb6ae7..c705df3d59 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -271,6 +271,7 @@ uint8_t *av_packet_new_side_data(AVPacket *pkt, enum 
AVPacketSideDataType type,
 data = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
 if (!data)
 return NULL;
+memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
 ret = av_packet_add_side_data(pkt, type, data, size);
 if (ret < 0) {
-- 
2.14.3 (Apple Git-98)

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