[libcxx-commits] [PATCH] D92110: [SystemZ][ZOS] Provide PATH_MAX macro for libcxx

Wed Dec 9 07:08:29 PST 2020

zibi added a comment.

On z/OS we have multiple file systems with different limits which does not allow to have just one constant for PATH_MAX. Same is true for other related limits like NAME_MAX. See the following references which justify the z/OS choice.

POSIX.1 document <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html>:
The values in the following list may be constants within an implementation or may vary from one pathname to another. For example, file systems or directories may have different characteristics.

A definition of one of the symbolic constants in the following list shall be omitted from the <limits.h> header on specific implementations where the corresponding value is equal to or greater than the stated minimum, but where the value can vary depending on the file to which it is applied. The actual value supported for a specific pathname shall be provided by the pathconf() function.

GNU document <https://www.gnu.org/software/libc/manual/html_node/Limits-for-Files.html#Limits-for-Files>
If the system allows different file systems or files to have different limits, then the macro is undefined; use pathconf or fpathconf to find out the limit that applies to a particular file. See Pathconf.

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https://reviews.llvm.org/D92110