cc -pthread -Wall -Wextra -Werror=implicit-function-declaration math/truncl.c -o math/truncl -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv math/truncl.c:10: warning: ignoring ‘#pragma STDC FENV_ACCESS’ [-Wunknown-pragmas] 10 | #pragma STDC FENV_ACCESS ON math/truncl.c: In function ‘test’: math/truncl.c:37:30: error: implicit declaration of function ‘truncl’ [-Wimplicit-function-declaration] 37 | long double output = truncl(input1); | ^~~~~~ math/truncl.c:9:1: note: include ‘’ or provide a declaration of ‘truncl’ 8 | #include "../basic.h" +++ |+#include 9 | math/truncl.c:37:30: warning: incompatible implicit declaration of built-in function ‘truncl’ [-Wbuiltin-declaration-mismatch] 37 | long double output = truncl(input1); | ^~~~~~ math/truncl.c:37:30: note: include ‘’ or provide a declaration of ‘truncl’