Re: [PATCH] sha512-buffer: port back to 32-bit-only hosts

[Paul Eggert]

On 2024-05-18 20:42, Collin Funk wrote:
> Out of personal interest, do you happen to know what platforms Emacs
> builds on that lack 64-bit types?

Emacs is a bit of a special case as it builds on verrry ooold platforms, 
including platforms no longer supported by their suppliers, and we're 
reasonably reluctant to require uint64_t except in platform-specific 
code where we know it's available. For example, there have been fairly 
recent (circa 2023) additions to Emacs working around the lack of 
uint64_t on older Android in certain compilation environments. For an 
example of these old environment's hassles (having to do with c89 vs c99 
compatibility, ouch), see 
<https://cs.android.com/android/_/android/platform/bionic/+/6d6731adc0cd0fb249a2b73a575e5ab2204643cc> 
which indicates this was an issue through at least Android Jelly Bean 
(2012), and I think the problem was even worse in earlier Android versions.

For what it's worth, in theory one must be careful with all the uint*_t 
types, as the standards say that integer overflow can have undefined 
behavior with any of them (because in theory they could all fit in 
'int'). One can use stdckdint.h macros to work around this theoretical 
issue, but of course that's annoying. I often find it easier just to use 
'unsigned int' or something wider.