"Implicit function error" build failure(s) — clang 5.0

PackageVersionSupposed error messageFull log Bug report
budgie-desktop 10.3.1-5src/applets/budgie-menu/budgiemenuapplet@sha/BudgieMenu.c:844:2: error: implicit declaration of function 'category_button_register_type' is invalid in C99 [-Werror,-Wimplicit-function-declaration] Log
freetype 2.8-0.2ttdebug.c:1935:16: error: implicitly declaring library function 'snprintf' with type 'int (char *, unsigned long, const char *, ...)' [-Werror,-Wimplicit-function-declaration] Log
pixman 0.34.0-1../../test/utils-prng.c:207:27: error: use of unknown builtin '__builtin_shuffle' [-Wimplicit-function-declaration] Log
smpq 1.6-1append.c:64:15: error: implicit declaration of function 'strcasecmp' [-Werror,-Wimplicit-function-declaration] Log

4 errors