From f80cc28124928d6f7ae0c535f8f40598e20cefb2 Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Wed, 24 Aug 2005 15:25:29 +0000 Subject: (stdopen): Revert to iterating over descriptors, but rather than using fstat, use fcntl with its F_GETFD flag, which is more efficient. Unlike the 2-syscall dup-close approach, this one doesn't apply any unnecessary pressure on the file descriptor pool -- thus there is one fewer way to fail. --- lib/stdopen.c | 52 ++++++++++++++++++++++------------------------------ 1 file changed, 22 insertions(+), 30 deletions(-) (limited to 'lib/stdopen.c') diff --git a/lib/stdopen.c b/lib/stdopen.c index 00914307d..c9d674fb6 100644 --- a/lib/stdopen.c +++ b/lib/stdopen.c @@ -30,18 +30,6 @@ #include #include -#ifndef STDIN_FILENO -# define STDIN_FILENO 0 -#endif - -#ifndef STDOUT_FILENO -# define STDOUT_FILENO 1 -#endif - -#ifndef STDERR_FILENO -# define STDERR_FILENO 2 -#endif - /* Try to ensure that each of the standard file numbers (0, 1, 2) is in use. Without this, each application would have to guard every call to open, dup, fopen, etc. with tests to ensure they @@ -51,25 +39,29 @@ bool stdopen (void) { - int fd = dup (STDIN_FILENO); - - if (0 <= fd) - close (fd); - else if (errno == EBADF) - fd = open ("/dev/null", O_WRONLY); - else - return false; + int fd; + bool ok = true; - if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) + for (fd = 0; fd <= 2; fd++) { - fd = open ("/dev/null", O_RDONLY); - if (fd == STDOUT_FILENO) - fd = dup (fd); - if (fd < 0) - return false; - - if (STDERR_FILENO < fd) - close (fd); + if (fcntl (fd, F_GETFD) < 0) + { + if (errno != EBADF) + ok = false; + else + { + static const int contrary_mode[] + = { O_WRONLY, O_RDONLY, O_RDONLY }; + int new_fd = open ("/dev/null", contrary_mode[fd]); + if (new_fd != fd) + { + if (0 <= new_fd) + close (new_fd); + ok = false; + } + } + } } - return true; + + return ok; } -- cgit v1.2.3-54-g00ecf