Typo in <sys/select.h>?

Lavrentiev, Anton (NIH/NLM/NCBI) [C] lavr@ncbi.nlm.nih.gov
Tue Jul 5 14:13:52 GMT 2022


There's some inconsistency between <sys/select.h> and <sys/param.h>:

sys/select.h has this:
 * Select uses bit masks of file descriptors in longs.
 * These macros manipulate such bit fields (the filesystem macros use chars).
 * FD_SETSIZE may be defined by the user, but the default here
 * should be >= NOFILE (param.h).
#ifndef FD_SETSIZE
#define FD_SETSIZE      64

Now, this is the relevant part of sys/param.h looks like this:
/* Max number of open files.  The Posix version is OPEN_MAX.  */
/* Number of fds is virtually unlimited in cygwin, but we must provide
   some reasonable value for Posix conformance */
#define NOFILE          8192

So it's either "<= NOFILE" that was actually meant to be there in the comment (or,
an equivalent "should NOT be > NOFILE"), or FD_SETSIZE should have been defined as 8192,
if the comment is actually correct.  Or maybe I'm missing something here :-)

I understand that if I redefined FD_SETSIZE in my code before including <sys/select.h>,
it'd work with whatever large (or small) fd_set I need, but that's not what I'm after.

Anton Lavrentiev
Contractor NIH/NLM/NCBI

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