cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations stdio/vsprintf.c -o stdio/vsprintf -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
stdio/vsprintf.c:5:50: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Werror,-Wimplicit-int]
int (*foo)(char *restrict, const char *restrict, va_list) = vsprintf;
                                                 ^
                                                 int
stdio/vsprintf.c:5:7: error: incompatible function pointer types initializing 'int (*)(char *restrict, const char *restrict, int)' with an expression of type 'int (char *, const char *, struct __va_list_tag *)' [-Werror,-Wincompatible-function-pointer-types]
int (*foo)(char *restrict, const char *restrict, va_list) = vsprintf;
      ^                                                     ~~~~~~~~
2 errors generated.