Re: PATH_MAX constant expression

[Bruno Haible]

Hi Jim,

> Bruno's comment (in the text you elided) suggests intent to have
> pathmax.h leave PATH_MAX undefined on the Hurd:
> 
>   >> I find it reasonable to use "#ifdef PATH_MAX" in front of every use of
>   >> PATH_MAX, like POSIX requires.
> 
> With such a change, each of the above uses would evoke a syntax error.

A package like coreutils can also do
  #ifndef PATH_MAX
  # define PATH_MAX 8192
  #endif
in its system.h.

Looking at both uses of PATH_MAX in coreutils (src/pwd.c:88 and
src/remove.c:186) the value of PATH_MAX is capped by 8192 or 16384 anyway.
So, on systems like GNU/Hurd, where filenames can have arbitrary size, you
are calling pathconf for no real purpose.

To me, this confirms that a generic pathmax.h (like the one in gnulib)
should only define PATH_MAX when it makes sense - like POSIX says -,
and that the handling of the GNU/Hurd case should be done on a case-by-case
basis:
  - Either a package-wide handling, or a per-file handling.
  - Either a fallback value of 8192, or a fallback value of
    pathconf ("/", _PC_PATH_MAX), or just a #ifdef test.

Bruno