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Re: [PATCH, libgfortran] Add overflow check to xmalloc


On 16 June 2014 08:20:09 Janne Blomqvist <blomqvist.janne@gmail.com> wrote:

On Sun, Jun 15, 2014 at 8:23 AM, Bernhard Reutner-Fischer
<rep.dot.nop@gmail.com> wrote:
>
>> >> On Tue, May 20, 2014 at 12:42 AM, Janne Blomqvist
>> >> <blomqvist.janne@gmail.com> wrote:
>> >>> On Thu, May 15, 2014 at 1:00 AM, Janne Blomqvist
>> >>> <blomqvist.janne@gmail.com> wrote:
>> >>>> Hi,
>> >>>>
>> >>>> a common malloc() pattern is "malloc(num_foo * sizeof(foo_t)", that
>> >>>> is, create space for an array of type foo_t with num_foo elements.
>> >>>> There is a slight danger here in that the multiplication can overflow
>> >>>> and wrap around, and then the caller thinks it has a larger array
>> >>>> than
>> >>>> what malloc has actually created. The attached patch changes the
>> >>>> libgfortran xmalloc() function to have an API similar to calloc()
>> >>>> with
>> >>>> two arguments, and the implementation checks for wraparound.
>> >>>
>> >>> Hello,
>> >>>
>> >>> attached is an updated patch which instead introduces a new function,
>> >>> xmallocarray, with the overflow check, and leaves the existing xmalloc
>> >>> as is. Thus avoiding the extra checking in the common case where one
>> >>> of the arguments to xmallocarray would be 1.
>> >>>
>> >>> Tested on x86_64-unknown-linux-gnu, Ok for trunk?
>> >>>
>
>
> I would prefer if xcmalloc would not be named xmallocarray.

Hmm, never heard of that one before, but I have no particular

Great, I fat-fingered it, meant xcalloc.

preference wrt the naming of the function. Ok with that rename?



--
Janne Blomqvist



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