Re: byteswap.h behavior

[Collin Funk]

On 5/12/24 12:38 PM, Paul Eggert wrote:
>> Also if we can agree upon making sure these are defined as functions,
>> what is the proper way to test it in a configure script? My instinct
>> tells me that assigning a function pointer to bswap_16, etc. would
>> fail if they are macros
> 
> I don't see the need to check that they are functions. POSIX does not require 
> endian.h symbols like be16toh to be defined as functions, and the glibc 
> manual doesn't mention endian.h, so it sounds like Gnulib-using code 
> shouldn't assume that these symbols are functions.

Yeah, I read the POSIX draft and it says that they may be macros. I
doubt the byteswap.h and endian.h functions are used with non-constant
expression arguments that often.

I worry though that in some cases programs will be accustomed to
glibc's behavior. Since all of the functions are just macros to static
inline functions in <bits/byteswap.h> arguments will only be evaluated
once. It seems like it could be the cause of some unexpected bugs...

Collin