abs
atof
atoi
calloc
__ctype_toupper_loc
__errno_location
exit
fclose
fflush
fopen
fprintf
fread
free
fseek
ftell
fwrite
__isoc23_sscanf
malloc
memcpy
memset
mkdir
printf
putchar
puts
realloc
remove
rename
snprintf
__stack_chk_fail
stderr
stdout
strcasecmp
strchr
strcmp
strdup
strlen
strncasecmp
strncmp
strncpy
strrchr
strstr
system
toupper
vfprintf // this
vsnprintf // also this