Re: From wchar_t to char32_t

[Paul Eggert]

On 2023-07-11 01:24, Bruno Haible wrote:
> Based on the comments in gnulib/lib/mbrtoc16.c, I think it should better
> clear the first 24, not 12, bytes of the struct. Otherwise it can be in
> a state where mbsinit() returns true but the mbrto* functions have
> undefined behaviour.

For mbcel all all that matters is mbrtoc32. Could you give an example of 
the undefined behavior there? I looked at the citrus implementations in 
current FreeBSD, OpenBSD and macOS and thought that 12 bytes is enough 
for mbrtoc32 on all their porting targets. NetBSD is a bit different and 
needs just a pointer width.

I didn't look at other functions like mbrlen and mbsinit, but would be 
mildly surprised if these functions differed, as mbrtoc32 is the 
fundamental function.

Assuming the optimization is valid, I suppose we could put it in Gnulib. 
Though it doesn't help much on GNU/Linux and so is lower priority.