It's always easy with hindsight to tell how to prevent something. In this case, a comment might have helped why the #ifdef was needed, eg void CloseAllFromTh

It's always easy with hindsight to tell how to prevent something. In this case, a comment might have helped why the #ifdef was needed, eg void CloseAllFromTheHardWay(int firstfd) //Code here must be async-signal-safe! Locks may be in indeterminate state { struct rlimit lim; getrlimit(RLIMIT_NOFILE,&lim); for (int fd=(lim.rlim_cur == RLIM_INFINITY ? 1024 : lim.rlim_cur);fd>=firstfd;--fd) close(fd); } Although to be honest, getrlimit isn't actually on the list here: https://man7.org/linux/man-pages/man7/signal-safety.7.html https://man7.org/linux/man-pages/man7/signal-safety.7.html But I hope that removing the comment or modifying code with a comment about async-signal-safe might have been noticed in review. The code you quoted only has the mention SAFE_IN_SIGHAND to suggest that this code might need to be async-signal-safe