daniel@daniel:~/tmp$ cat wtf.c
#include <stdio.h>
typedef struct Test {
    int a;
    char *b;
} Test;
int main() {
    Test t = { .a = (1+2,3+4), .b = ("foo","bar")};
    printf("%d:%s\n", t.a, t.b);
}
daniel@daniel:~/tmp$ clang wtf.c -o wtf
wtf.c:9:23: warning: expression result unused [-Wunused-value]
    Test t = { .a = (1+2,3+4), .b = ("foo","bar")};
                     ~^~
wtf.c:9:38: warning: expression result unused [-Wunused-value]
    Test t = { .a = (1+2,3+4), .b = ("foo","bar")};
                                     ^~~~~
2 warnings generated.
daniel@daniel:~/tmp$ ./wtf
7:bar