Re: [PATCH] readelf: use fseeko for elf files >= 2 GiB on x86_64-mingw32

[Jan Beulich <jbeulich@suse.com>]

On 16.11.2022 11:09, Mike Frysinger wrote:
> On 15 Nov 2022 08:12, Alan Modra via Binutils wrote:
>> On Mon, Nov 14, 2022 at 09:52:30AM -0600, Brett Werling via Binutils wrote:
>>> On Mon, Nov 14, 2022 at 9:30 AM Jan Beulich <jbeulich@suse.com> wrote:
>>>> On 14.11.2022 16:03, Brett Werling via Binutils wrote:
>>>>> Switch all fseek calls to fseeko and cast the given offset as an off_t
>>>>> accordingly. When building readelf for x86_64-mingw32, a long will only
>>>>> be 32 bits wide. If the elf file in question is >= 2 GiB, that is
>>>>> greater than the max long value, and therefore fseek will fail
>>>>> indicating that the offset is negative.
>>>>>
>>>>> To work around this and support up to 4 GiB, we switch to using fseeko
>>>>> and cast the unsigned long offsets as off_t values because the size of
>>>>> off_t is 64 bits on x86_64-mingw32.
>>>>
>>>> Is fseeko() uniformly available on all platforms binutils can be built
>>>> for? I'm afraid the answer is no, so at least you'd need to introduce
>>>> some configure logic for this plus some abstraction.
>>>
>>> I think you are correct, this will need some conditional logic to be "safe"
>>> to
>>> include, and even then the casting to off_t would become a little more
>>> complicated. I will look deeper into what can be done here.
>>
>> See bfd/bfdio.c and bfd/configure.ac
> 
> should we look at bfd using gnulib ?  growing our own portability layer sounds
> like a lot of dupicative effort ...

Right now binutils can be built and run on pretty old distros. Unless a pretty
old gnulib would be taken as the baseline, this property would be lost with
the introduction of such a dependency.

Jan