Issue #21128 has been reported by collinfunk (Collin Funk). ---------------------------------------- Bug #21128: dir.c defines O_CLOEXEC before it is defined by the system. https://bugs.ruby-lang.org/issues/21128 * Author: collinfunk (Collin Funk) * Status: Open * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- Building from master commit hash bfcf36fe2243d34a01b5707754be9164849150c9 on GNU/Linux, I see: ``` compiling dir.c In file included from /usr/include/bits/fcntl.h:61, from /usr/include/fcntl.h:35, from dir.c:39: /usr/include/bits/fcntl-linux.h:144:10: warning: "O_CLOEXEC" redefined 144 | # define O_CLOEXEC __O_CLOEXEC /* Set close_on_exec. */ | ^~~~~~~~~ dir.c:26:11: note: this is the location of the previous definition 26 | # define O_CLOEXEC 0 | ^~~~~~~~~ ``` This is because the file includes unistd.h before falling back to 0 for O_CLOEXEC. But glibc requires inclusion of fcntl.h for O_CLOEXEC. Since that file is included after, it is redefined. The C standard leaves the behavior of redefining a variable undefined and it is a simple fix, so I will create a pull request. -- https://bugs.ruby-lang.org/