Re: mmap quiet failure - all reads are 0x00
Re: mmap quiet failure - all reads are 0x00
- Subject: Re: mmap quiet failure - all reads are 0x00
- From: Michael David Crawford <email@hidden>
- Date: Fri, 05 Feb 2016 18:32:54 -0800
Perhaps it is a bug unrelated to mmap, that screws up some of your
state, then later it causes the mmap to fail.
Or perhaps the mmap succeeds, but the bytes your are reading are
coming from some other place.
There are many debugging techniques, such as using assertions, guard
malloc etc. But don't just focus narrowly on the mmap itself.
Michael David Crawford, Baritone
email@hidden
One Must Not Trifle With Wizards For It Makes Us Soggy And Hard To Light.
On Fri, Feb 5, 2016 at 4:36 PM, Jens Alfke <email@hidden> wrote:
>
>> On Feb 5, 2016, at 10:09 AM, Trygve Inda <email@hidden> wrote:
>>
>> It seems like no matter what is in the mmap file, when I read from it I get
>> 0x00 for every byte and no error or exception is generated. I can't
>> reproduce it as it is very random. Quitting and relaunching solves it.
>
> That sounds strange to me. I’m not an expert at mmap, but my understanding is that if a page fault can’t be satisfied the memory access will fail with a signal. You might ask on the darwin-userlevel list since this is really a Unix-level question.
>
> —Jens
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