Hi Christian, On 5/4/2026 11:39 AM, Christian Franke via Cygwin wrote:
Could be reproduced with 3.6.9 and current HEAD.Testcase: $ uname -r # or 3.6.9-1.x86_64 3.7.0-0.483.ga1f347c0d5b8.x86_64 $ cat openmany.c #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <sys/stat.h> int main() { for (int i = 0; i < 10000; i++) { char name[32]; snprintf(name, sizeof(name), "file-%04d.tmp", i); errno = 0; int fd = open(name, O_WRONLY | O_CREAT | O_EXCL, 0666); if (fd >= 0) continue; printf("open(%s, ...)=%d (errno=%d)\n", name, fd, errno); struct stat st; printf("stat(%s, ...)=%d\n", name, stat(name, &st)); break; } return 0; } $ gcc -o openmany openmany.c $ ls file-*.tmp ls: cannot access 'file-*.tmp': No such file or directory $ ulimit -n 3200 $ ./openmany open(file-3197.tmp, ...)=-1 (errno=24) stat(file-3197.tmp, ...)=0 $ ls file-*.tmp file-0000.tmp file-0001.tmp ... file-3195.tmp file-3196.tmp file-3197.tmp $ grep -w 24 /usr/include/sys/errno.h #define EMFILE 24 /* File descriptor value too large */ Looks like the fd is allocated too late.
Thanks for the report and especially for the STC. It is during fdtable extension that the limit is checked; by then NtCreateFile() has already been called successfully. We need to consider a fix that avoids needlessly creating a file that can't be operated on anyway.
..mark -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
