On 04/05/2021 15:57, Gedare Bloom wrote:
On Tue, May 4, 2021 at 6:55 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de> wrote:
On 04/05/2021 14:52, Joel Sherrill wrote:
On Tue, May 4, 2021, 7:12 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de
<mailto:sebastian.hu...@embedded-brains.de>> wrote:
On 04/05/2021 14:07, Joel Sherrill wrote:
> This is undefined behaviour and I would rather they all return NULL.
As far as I understood the POSIX text, it is implementation-defined
behaviour and POSIX gives two valid implementation options. The patch
removed some code (less code is always good) and now we are in line
with
Linux and FreeBSD.
We should be more focused on correctness. We don't agree with not
checking null pointers as arguments either.
If the application uses the memory returned, there is no guarantee on
the size and this leads quite naturally to a buffer overflow.
I don't care that much if we return a unique pointer or NULL, but it
should be consistent across the directives.
I agree that we should aim to make the implementation-defined behavior
consistent. I can see some advantages to returning a pointer,
including:
* code is simpler
* can ensure that free() is paired properly
* NULL is only returned if memory is exhausted
It is then incumbent on programmers to be sure to pass size > 0 to
malloc. I checked and from what I can tell in bsps/ we mostly have
that occurring in the device drivers there.
The only disadvantage I see is that programmers who relied on the
previous behavior to catch malloc(0) as NULL return would have a
problem. Whether they should have been doing that in the first place
is suspect, and non-portable.
From an error propagation point of view, Joel has a valid point.
However, if we care about this, then we should also sanitize return by
reference values under error conditions:
https://lists.rtems.org/pipermail/devel/2021-March/065840.html
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