John E. Malmberg wrote: > > [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/getrlimit.html > According to that link, a system is not required to fail a request for a > file descriptor to be created higher than RLIMIT_NOFILE.
Not true. [1] refers to [2], and [2] as well as [3] say that getrlimit(RLIMIT_NOFILE) is "one greater than the maximum value that the system may assign to a newly-created descriptor." The other sentence is just an explanation of the effect of this definition. But I admit that you may have been confused because the comments in gnulib were misleading. > Attached is a patch for the test to pass on OpenVMS. Not usable: Comments are wrong, and I prefer a 'case' statement over a #ifdef that renders the test a dummy. Here's what I'm pushing. [1] http://pubs.opengroup.org/onlinepubs/7908799/xsh/getdtablesize.html [2] http://pubs.opengroup.org/onlinepubs/7908799/xsh/getrlimit.html [3] http://pubs.opengroup.org/onlinepubs/009695399/functions/getrlimit.html 2017-07-15 Bruno Haible <br...@clisp.org> getdtablesize: Add minimal support for OpenVMS. Reported by John E. Malmberg <wb8...@qsl.net>. * modules/getdtablesize (Description): Fix. * lib/getdtablesize.c: Fix comment. * m4/getdtablesize.m4 (gl_FUNC_GETDTABLESIZE): Don't replace the getdtablesize() function, even though the test fails. * doc/glibc-functions/getdtablesize.texi: Reference SUSv2. Describe limitation on OpenVMS. diff --git a/doc/glibc-functions/getdtablesize.texi b/doc/glibc-functions/getdtablesize.texi index 921c985..b7a16d1 100644 --- a/doc/glibc-functions/getdtablesize.texi +++ b/doc/glibc-functions/getdtablesize.texi @@ -2,6 +2,8 @@ @subsection @code{getdtablesize} @findex getdtablesize +SUSv2 specification: @url{http://pubs.opengroup.org/onlinepubs/7908799/xsh/getdtablesize.html} + Gnulib module: getdtablesize Portability problems fixed by Gnulib: @@ -22,4 +24,8 @@ Android LP32, Cygwin 1.7.25. Portability problems not fixed by Gnulib: @itemize +@item +On OpenVMS, this function returns the maximum number of open file descriptors +in a process. The possible values of file descriptors are not constrained by +this function. @end itemize diff --git a/lib/getdtablesize.c b/lib/getdtablesize.c index c356cf4..a092863 100644 --- a/lib/getdtablesize.c +++ b/lib/getdtablesize.c @@ -1,4 +1,4 @@ -/* getdtablesize() function for platforms that don't have it. +/* getdtablesize() function: Return maximum possible file descriptor value + 1. Copyright (C) 2008-2017 Free Software Foundation, Inc. Written by Bruno Haible <br...@clisp.org>, 2008. diff --git a/m4/getdtablesize.m4 b/m4/getdtablesize.m4 index 1af2a24..f1e4f5f 100644 --- a/m4/getdtablesize.m4 +++ b/m4/getdtablesize.m4 @@ -1,4 +1,4 @@ -# getdtablesize.m4 serial 6 +# getdtablesize.m4 serial 7 dnl Copyright (C) 2008-2017 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, @@ -12,29 +12,43 @@ AC_DEFUN([gl_FUNC_GETDTABLESIZE], AC_CHECK_DECLS_ONCE([getdtablesize]) if test $ac_cv_func_getdtablesize = yes && test $ac_cv_have_decl_getdtablesize = yes; then - # Cygwin 1.7.25 automatically increases the RLIMIT_NOFILE soft limit - # up to an unchangeable hard limit; all other platforms correctly - # require setrlimit before getdtablesize() can report a larger value. AC_CACHE_CHECK([whether getdtablesize works], [gl_cv_func_getdtablesize_works], - [AC_RUN_IFELSE([ - AC_LANG_PROGRAM([[#include <unistd.h>]], - [int size = getdtablesize(); - if (dup2 (0, getdtablesize()) != -1) - return 1; - if (size != getdtablesize()) - return 2; - ])], - [gl_cv_func_getdtablesize_works=yes], - [gl_cv_func_getdtablesize_works=no], - [case "$host_os" in - cygwin*) # on cygwin 1.5.25, getdtablesize() automatically grows - gl_cv_func_getdtablesize_works="guessing no" ;; - *) gl_cv_func_getdtablesize_works="guessing yes" ;; - esac]) + [dnl There are two concepts: the "maximum possible file descriptor value + 1" + dnl and the "maximum number of open file descriptors in a process". + dnl Per SUSv2 and POSIX, getdtablesize() should return the first one. + dnl On most platforms, the first and the second concept are the same. + dnl On OpenVMS, however, they are different and getdtablesize() returns + dnl the second one; thus the test below fails. But we don't care + dnl because there's no good way to write a replacement getdtablesize(). + case "$host_os" in + vms*) gl_cv_func_getdtablesize_works="no (limitation)" ;; + *) + dnl Cygwin 1.7.25 automatically increases the RLIMIT_NOFILE soft + dnl limit up to an unchangeable hard limit; all other platforms + dnl correctly require setrlimit before getdtablesize() can report + dnl a larger value. + AC_RUN_IFELSE([ + AC_LANG_PROGRAM([[#include <unistd.h>]], + [int size = getdtablesize(); + if (dup2 (0, getdtablesize()) != -1) + return 1; + if (size != getdtablesize()) + return 2; + ])], + [gl_cv_func_getdtablesize_works=yes], + [gl_cv_func_getdtablesize_works=no], + [case "$host_os" in + cygwin*) # on cygwin 1.5.25, getdtablesize() automatically grows + gl_cv_func_getdtablesize_works="guessing no" ;; + *) gl_cv_func_getdtablesize_works="guessing yes" ;; + esac + ]) + ;; + esac ]) case "$gl_cv_func_getdtablesize_works" in - *yes) ;; + *yes | "no (limitation)") ;; *) REPLACE_GETDTABLESIZE=1 ;; esac else diff --git a/modules/getdtablesize b/modules/getdtablesize index e458f3a..f33fcb5 100644 --- a/modules/getdtablesize +++ b/modules/getdtablesize @@ -1,5 +1,5 @@ Description: -getdtablesize() function: return maximum number of file descriptors. +getdtablesize() function: return tight upper bound for file descriptor values. Files: lib/getdtablesize.c
