Vulnerabilities Induced by Migrating to 64-Bit Platforms [pdf]

Re:Vulnerabilities Induced by Migrating to 64-Bit Platforms ... by jibsen on Sunday September 18, 2016 @02:01PM (#12526313)

It's worth noting that ssize_t is a POSIX type, and is only guaranteed to have the range [-1, SSIZE_MAX] (basically a size type with one error value) [1]. If you need negative sizes, then ptrdiff_t is perhaps better.

[1]: http://pubs.opengroup.org/onlinepubs/009696699/basedefs/sys/...

[ Parent | on HN ]

Re:Vulnerabilities Induced by Migrating to 64-Bit Platforms ... by vardump on Sunday September 18, 2016 @03:14PM (#12526687)

Thanks for the correction!

> only guaranteed to have the range [-1, SSIZE_MAX]

Oh, that's a weird type. I wonder if any compiler implementation encodes it with -1 bias, so that all bits 0 means "-1".

It could cause a disaster if/when ssize_t is encoded as anything else but standard twos complement signed number...

[ Parent | on HN ]

Re:Vulnerabilities Induced by Migrating to 64-Bit Platforms ... by colejohnson66 on Sunday September 18, 2016 @03:26PM (#12526745)

I'd assume it's just an unsigned number with 0xFF... representing -1. So counting would go (assuming 8 bits)

    0xFC SSIZE_MAX - 2
    0xFD SSIZE_MAX - 1
    0xFE SIZE_MAX
    0xFF -1

That makes more sense to me than a bias that the compiler would have to know about.

[ Parent | on HN ]