The AVBPrint API guarantees that the string buffer is always
zero-terminated; in order to honour this guarantee, there
obviously must be a string buffer at all and it must have
a size >= 1. Therefore av_bprint_init_for_buffer() treats
passing a NULL buffer or size == 0 as invalid data that
leads to undefined behaviour, namely NPD in case NULL is provided
or a write to a buffer of size 0 in case size == 0.
But it would be easy to support this, namely by using the internal
buffer with AV_BPRINT_SIZE_COUNT_ONLY in case size == 0.
There is a reason to allow this: Several functions like
av_channel_(description|name) are actually wrappers
around corresponding AVBPrint functions. They accept user
provided buffers and are supposed to return the required
size of the buffer, which would allow the user to call
it once to get the required buffer size and call it once
more after having allocated the buffer.
If av_bprint_init_for_buffer() treats size == 0 as invalid,
all these users would need to check for this themselves
and basically add the same codeblock that this patch
adds to av_bprint_init_for_buffer().
This change is in line with e.g. snprintf() which also allows
the pointer to be NULL in case size is zero.
This fixes Coverity issues #1503074, #1503076 and #1503082;
all of these issues are about providing NULL to the channel-layout
functions that are wrappers around AVBPrint versions.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
MSVC does not allow passing file pointers between libs
This API can thus not work with MSVC and as it was very recently added
and its it was in no release its removial should not cause any problems
A better API will be implemented, but its not finished yet, this revert is
to avoid potentially blocking the release
Found-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
Reveiwed-by: Nicolas George <nicolas.george@normalesup.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
The escape API will be useful to perform escaping programmatically, which
is required when crafting argument strings, and will be used for context
printing as well.
This is based on the ffescape tool code, with a few extensions and fixes.
