# Extra Clang Tools 18.1.8 documentation

## clang-tidy - bugprone-unused-return-value

# bugprone-unused-return-value

Warns on unused function return values. The checked functions can be configured.

## Options

CheckedFunctions

  Semicolon-separated list of functions to check. The function is checked if the name and scope matches, with any arguments. By default the following functions are checked: `std::async, std::launder, std::remove, std::remove_if, std::unique, std::unique_ptr::release, std::basic_string::empty, std::vector::empty, std::back_inserter, std::distance, std::find, std::find_if, std::inserter, std::lower_bound, std::make_pair, std::map::count, std::map::find, std::map::lower_bound, std::multimap::equal_range, std::multimap::upper_bound, std::set::count, std::set::find, std::setfill, std::setprecision, std::setw, std::upper_bound, std::vector::at, bsearch, ferror, feof, isalnum, isalpha, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, iswalnum, iswprint, iswspace, isxdigit, memchr, memcmp, strcmp, strcoll, strncmp, strpbrk, strrchr, strspn, strstr, wcscmp, access, bind, connect, difftime, dlsym, fnmatch, getaddrinfo, getopt, htonl, htons, iconv_open, inet_addr, isascii, isatty, mmap, newlocale, openat, pathconf, pthread_equal, pthread_getspecific, pthread_mutex_trylock, readdir, readlink, recvmsg, regexec, scandir, semget, setjmp, shm_open, shmget, sigismember, strcasecmp, strsignal, ttyname`

  - `std::async()`. Not using the return value makes the call synchronous.

  - `std::launder()`. Not using the return value usually means that the function interface was misunderstood by the programmer. Only the returned pointer is “laundered”, not the argument.

  - `std::remove()`, `std::remove_if()` and `std::unique()`. The returned iterator indicates the boundary between elements to keep and elements to be removed. Not using the return value means that the information about which elements to remove is lost.

  - `std::unique_ptr::release()`. Not using the return value can lead to resource leaks if the same pointer isn’t stored anywhere else. Often, ignoring the `release()` return value indicates that the programmer confused the function with `reset()`.

  - `std::basic_string::empty()` and `std::vector::empty()`. Not using the return value often indicates that the programmer confused the function with `clear()`.

CheckedReturnTypes

  Semicolon-separated list of function return types to check. By default the following function return types are checked: ::std::error_code, ::std::error_condition, ::std::errc, ::std::expected, ::boost::system::error_code

AllowCastToVoid

  Controls whether casting return values to `void` is permitted. Default: false.

cert-err33-c is an alias of this check that checks a fixed and large set of standard library functions.