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1.. title:: clang-tidy - bugprone-signal-handler2 3bugprone-signal-handler4=======================5 6Finds specific constructs in signal handler functions that can cause undefined7behavior. The rules for what is allowed differ between C++ language versions.8 9Checked signal handler rules for C:10 11- Calls to non-asynchronous-safe functions are not allowed.12 13Checked signal handler rules for up to and including C++14:14 15- Calls to non-asynchronous-safe functions are not allowed.16- C++-specific code constructs are not allowed in signal handlers.17 In other words, only the common subset of C and C++ is allowed to be used.18- Calls to functions with non-C linkage are not allowed (including the signal19 handler itself).20 21The check is disabled on C++17 and later.22 23Asynchronous-safety is determined by comparing the function's name against a24set of known functions. In addition, the function must come from a system25header include and in a global namespace. The (possible) arguments passed to26the function are not checked. Any function that cannot be determined to be27asynchronous-safe is assumed to be non-asynchronous-safe by the check,28including user functions for which only the declaration is visible.29Calls to user-defined functions with visible definitions are checked30recursively.31 32This check implements the CERT C Coding Standard rule33`SIG30-C. Call only asynchronous-safe functions within signal handlers34<https://www.securecoding.cert.org/confluence/display/c/SIG30-C.+Call+only+asynchronous-safe+functions+within+signal+handlers>`_35and the rule36`MSC54-CPP. A signal handler must be a plain old function37<https://wiki.sei.cmu.edu/confluence/display/cplusplus/MSC54-CPP.+A+signal+handler+must+be+a+plain+old+function>`_.38It has the alias names ``cert-sig30-c`` and ``cert-msc54-cpp``.39 40Options41-------42 43.. option:: AsyncSafeFunctionSet44 45 Selects which set of functions is considered as asynchronous-safe46 (and therefore allowed in signal handlers). It can be set to the following values:47 48 - `minimal`49 Selects a minimal set that is defined in the CERT SIG30-C rule.50 and includes functions ``abort()``, ``_Exit()``, ``quick_exit()`` and51 ``signal()``.52 - `POSIX`53 Selects a larger set of functions that is listed in POSIX.1-2017 (see `this54 link55 <https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03>`_56 for more information). The following functions are included:57 ``_Exit``, ``_exit``, ``abort``, ``accept``, ``access``, ``aio_error``,58 ``aio_return``, ``aio_suspend``, ``alarm``, ``bind``, ``cfgetispeed``,59 ``cfgetospeed``, ``cfsetispeed``, ``cfsetospeed``, ``chdir``, ``chmod``,60 ``chown``, ``clock_gettime``, ``close``, ``connect``, ``creat``, ``dup``,61 ``dup2``, ``execl``, ``execle``, ``execv``, ``execve``, ``faccessat``,62 ``fchdir``, ``fchmod``, ``fchmodat``, ``fchown``, ``fchownat``, ``fcntl``,63 ``fdatasync``, ``fexecve``, ``ffs``, ``fork``, ``fstat``, ``fstatat``,64 ``fsync``, ``ftruncate``, ``futimens``, ``getegid``, ``geteuid``,65 ``getgid``, ``getgroups``, ``getpeername``, ``getpgrp``, ``getpid``,66 ``getppid``, ``getsockname``, ``getsockopt``, ``getuid``, ``htonl``,67 ``htons``, ``kill``, ``link``, ``linkat``, ``listen``, ``longjmp``,68 ``lseek``, ``lstat``, ``memccpy``, ``memchr``, ``memcmp``, ``memcpy``,69 ``memmove``, ``memset``, ``mkdir``, ``mkdirat``, ``mkfifo``, ``mkfifoat``,70 ``mknod``, ``mknodat``, ``ntohl``, ``ntohs``, ``open``, ``openat``,71 ``pause``, ``pipe``, ``poll``, ``posix_trace_event``, ``pselect``,72 ``pthread_kill``, ``pthread_self``, ``pthread_sigmask``, ``quick_exit``,73 ``raise``, ``read``, ``readlink``, ``readlinkat``, ``recv``, ``recvfrom``,74 ``recvmsg``, ``rename``, ``renameat``, ``rmdir``, ``select``, ``sem_post``,75 ``send``, ``sendmsg``, ``sendto``, ``setgid``, ``setpgid``, ``setsid``,76 ``setsockopt``, ``setuid``, ``shutdown``, ``sigaction``, ``sigaddset``,77 ``sigdelset``, ``sigemptyset``, ``sigfillset``, ``sigismember``,78 ``siglongjmp``, ``signal``, ``sigpause``, ``sigpending``, ``sigprocmask``,79 ``sigqueue``, ``sigset``, ``sigsuspend``, ``sleep``, ``sockatmark``,80 ``socket``, ``socketpair``, ``stat``, ``stpcpy``, ``stpncpy``,81 ``strcat``, ``strchr``, ``strcmp``, ``strcpy``, ``strcspn``, ``strlen``,82 ``strncat``, ``strncmp``, ``strncpy``, ``strnlen``, ``strpbrk``,83 ``strrchr``, ``strspn``, ``strstr``, ``strtok_r``, ``symlink``,84 ``symlinkat``, ``tcdrain``, ``tcflow``, ``tcflush``, ``tcgetattr``,85 ``tcgetpgrp``, ``tcsendbreak``, ``tcsetattr``, ``tcsetpgrp``,86 ``time``, ``timer_getoverrun``, ``timer_gettime``, ``timer_settime``,87 ``times``, ``umask``, ``uname``, ``unlink``, ``unlinkat``, ``utime``,88 ``utimensat``, ``utimes``, ``wait``, ``waitpid``, ``wcpcpy``,89 ``wcpncpy``, ``wcscat``, ``wcschr``, ``wcscmp``, ``wcscpy``, ``wcscspn``,90 ``wcslen``, ``wcsncat``, ``wcsncmp``, ``wcsncpy``, ``wcsnlen``, ``wcspbrk``,91 ``wcsrchr``, ``wcsspn``, ``wcsstr``, ``wcstok``, ``wmemchr``, ``wmemcmp``,92 ``wmemcpy``, ``wmemmove``, ``wmemset``, ``write``93 94 The function ``quick_exit`` is not included in the POSIX list but it95 is included here in the set of safe functions.96 97 The default value is `POSIX`.98