Re: supporting strings > 2 GB

[Paul Eggert]

On 10/13/19 12:50 PM, Bruno Haible wrote:
> The C or POSIX standards deal only with layer 1). However, layer 2) is
> essential for programs, to make the use of the new APIs easy.

Right, and I see the need for two layers. I'm still not seeing, though, the 
exact division between the two layers in this instance.

With large file support, POSIX took an old function lseek that used 'long', and 
said that lseek should use the new type 'off_t' instead. Old implementations 
could simply add 'typedef long off_t;' and conform. There is no OFF_MAX or 
PRIdOFF because off_t is not part of ISO C. Programs define _FILE_OFFSET_BITS to 
choose which off_t they get.

A difference here is that we'd be proposing a change to ISO C (it could be done 
only in POSIX, but it's really a change to the C standard). In ISO C there's a 
tradition that types like 'ptrdiff_t' all have macros like PTRDIFF_MAX, PRIdPTR, 
etc., and so presumably this tradition should apply to printf_len_t.

If we take this approach, there should be no need for %ln vs %n or %**d vs %*d; 
programs that define _PRINTF_LARGE will get a wide printf_len_t and things will 
"just work" if programs consistently use printf_len_t instead of int (and use 
the related macros too).