Hi,
On 08.02.2016 00:07, Matt Turner wrote:
On Sun, Feb 7, 2016 at 1:37 PM, Juha-Pekka Heikkilä
<juhapekka.heikk...@gmail.com> wrote:
I know there are lot of places where there is malloc unchecked still
-- and then there is ralloc which is a story of its own. Reason why I
think checking these would be remotely useful in windows only (or
other way around, not under linux kernel) is on Windows one can get
the null pointer from malloc. On Androids I think memory over
committing has always been enabled and on Linux I suspect I belong to
the minority who like to set ulimits for memory.
I agree checking these mostly is quite useless but there are those
corners where it may suddenly become valuable. When process is running
and everything has settled it will be weird if hit any of these checks
but any code which is run when process is starting I notice is the
place where things will fail if they fail. This is of course just my
opinion about the value of these checks but I really dislike
possibility of segfault when it is coming from a library.
I didn't quickly notice where _mesa_error() get more heap. Stack it of
course needs but when I did stress test these _mesa_error() did still
work. Cannot promise my test was 100% correct though, I think it was
over year ago when I was playing with it.
There's no guarantee that fprintf() doesn't call malloc. In fact, glibc's does.
If one is just concerned about not calling something that may use
malloc, the functions listed by "man 7 signal" as async-signal-safe are
safe in that respect (one cannot use malloc within signal handler context).
Adding these checks is really useless.
If one runs out of memory when overcommit is enabled, in theory about
anything the program does, can cause it to use more memory. Not just
allocations. E.g. running code for handling an error, may cause kernel
to need to allocate space to page that code into RAM. This can happen
even if the isn't run for the first time, if kernel had dropped that
page from RAM.
- Eero
(Modern desktop systems don't work well without overcommit. Having
system with programs that have large number of threads or otherwise
hardly used memory mapping, like is case e.g. on fork, could be in
trouble, unless they have overtly large amounts of RAM.)
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