> cat /tmp/1.c #include <stdbool.h> void foo() { bool y = true; void (*x)() = y; } > gcc -c -Wall -Wextra /tmp/1.c /tmp/1.c: In function ‘foo’: /tmp/1.c:4:16: error: incompatible types when initializing type ‘void (*)()’ using type ‘_Bool’ void (*x)() = y; ^ ... > clang -c -Wall -Wextra /tmp/1.c /tmp/1.c:4:9: warning: incompatible integer to pointer conversion initializing 'void (*)()' with an expression of type 'bool' [-Wint-conversion] void (*x)() = y; ^ ~