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1.. title:: clang-tidy - cert-err33-c2 3cert-err33-c4============5 6Warns on unused function return values. Many of the standard library functions7return a value that indicates if the call was successful. Ignoring the returned8value can cause unexpected behavior if an error has occurred. The following9functions are checked:10 11* aligned_alloc()12* asctime_s()13* at_quick_exit()14* atexit()15* bsearch()16* bsearch_s()17* btowc()18* c16rtomb()19* c32rtomb()20* calloc()21* clock()22* cnd_broadcast()23* cnd_init()24* cnd_signal()25* cnd_timedwait()26* cnd_wait()27* ctime_s()28* fclose()29* fflush()30* fgetc()31* fgetpos()32* fgets()33* fgetwc()34* fopen()35* fopen_s()36* fprintf()37* fprintf_s()38* fputc()39* fputs()40* fputwc()41* fputws()42* fread()43* freopen()44* freopen_s()45* fscanf()46* fscanf_s()47* fseek()48* fsetpos()49* ftell()50* fwprintf()51* fwprintf_s()52* fwrite()53* fwscanf()54* fwscanf_s()55* getc()56* getchar()57* getenv()58* getenv_s()59* gets_s()60* getwc()61* getwchar()62* gmtime()63* gmtime_s()64* localtime()65* localtime_s()66* malloc()67* mbrtoc16()68* mbrtoc32()69* mbsrtowcs()70* mbsrtowcs_s()71* mbstowcs()72* mbstowcs_s()73* memchr()74* mktime()75* mtx_init()76* mtx_lock()77* mtx_timedlock()78* mtx_trylock()79* mtx_unlock()80* printf_s()81* putc()82* putwc()83* raise()84* realloc()85* remove()86* rename()87* setlocale()88* setvbuf()89* scanf()90* scanf_s()91* signal()92* snprintf()93* snprintf_s()94* sprintf()95* sprintf_s()96* sscanf()97* sscanf_s()98* strchr()99* strerror_s()100* strftime()101* strpbrk()102* strrchr()103* strstr()104* strtod()105* strtof()106* strtoimax()107* strtok()108* strtok_s()109* strtol()110* strtold()111* strtoll()112* strtoumax()113* strtoul()114* strtoull()115* strxfrm()116* swprintf()117* swprintf_s()118* swscanf()119* swscanf_s()120* thrd_create()121* thrd_detach()122* thrd_join()123* thrd_sleep()124* time()125* timespec_get()126* tmpfile()127* tmpfile_s()128* tmpnam()129* tmpnam_s()130* tss_create()131* tss_get()132* tss_set()133* ungetc()134* ungetwc()135* vfprintf()136* vfprintf_s()137* vfscanf()138* vfscanf_s()139* vfwprintf()140* vfwprintf_s()141* vfwscanf()142* vfwscanf_s()143* vprintf_s()144* vscanf()145* vscanf_s()146* vsnprintf()147* vsnprintf_s()148* vsprintf()149* vsprintf_s()150* vsscanf()151* vsscanf_s()152* vswprintf()153* vswprintf_s()154* vswscanf()155* vswscanf_s()156* vwprintf_s()157* vwscanf()158* vwscanf_s()159* wcrtomb()160* wcschr()161* wcsftime()162* wcspbrk()163* wcsrchr()164* wcsrtombs()165* wcsrtombs_s()166* wcsstr()167* wcstod()168* wcstof()169* wcstoimax()170* wcstok()171* wcstok_s()172* wcstol()173* wcstold()174* wcstoll()175* wcstombs()176* wcstombs_s()177* wcstoumax()178* wcstoul()179* wcstoull()180* wcsxfrm()181* wctob()182* wctrans()183* wctype()184* wmemchr()185* wprintf_s()186* wscanf()187* wscanf_s()188 189This check is an alias of check :doc:`bugprone-unused-return-value190<../bugprone/unused-return-value>` with a fixed set of functions.191 192Suppressing issues by casting to ``void`` is enabled by default and can be193disabled by setting `AllowCastToVoid` option to `false`.194 195The check corresponds to a part of CERT C Coding Standard rule `ERR33-C.196Detect and handle standard library errors197<https://wiki.sei.cmu.edu/confluence/display/c/ERR33-C.+Detect+and+handle+standard+library+errors>`_.198The list of checked functions is taken from the rule, with following exception:199 200* The check can not differentiate if a function is called with ``NULL``201 argument. Therefore the following functions are not checked:202 ``mblen``, ``mbrlen``, ``mbrtowc``, ``mbtowc``, ``wctomb``, ``wctomb_s``203