empty_struct_test.sh

# Example & test for FTP-015

cat > empty_struct_test.c << EOF

#include <stdio.h>

// FIDL:
// struct Empty {};

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-length-array"
    typedef int FIDLEmptyStructInternal[0];
#pragma clang diagnostic pop

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wc++-compat"
#pragma clang diagnostic ignored "-Wextern-c-compat"
    typedef struct {
        FIDLEmptyStructInternal reserved;
    } Empty;
#pragma clang diagnostic pop

int main() {
    Empty e;
    printf("sizeof(Empty): %zu\n", sizeof(e));

    return 0;
}
EOF

clang empty_struct_test.c -Weverything -O0 -o empty_struct_test_c_O0 && ./empty_struct_test_c_O0
clang empty_struct_test.c -Weverything -O3 -o empty_struct_test_c_O3 && ./empty_struct_test_c_O3

cat > empty_struct_test.cc << EOF

#include <stdio.h>

// FIDL:
// struct Empty {};

extern "C" {  // test including header files intended for C translation units
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-length-array"
    typedef int FIDLEmptyStructInternal[0];
#pragma clang diagnostic pop

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wc++-compat"
#pragma clang diagnostic ignored "-Wextern-c-compat"
    typedef struct {
        FIDLEmptyStructInternal reserved;
    } CEmpty;
#pragma clang diagnostic pop
}

typedef struct {
private:
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-length-array"
#pragma clang diagnostic ignored "-Wunused-private-field"
    int reserved[0];
#pragma clang diagnostic pop

public:
    void Foo() {
        // Can attach methods to an empty struct too, just like a normal struct.
        printf("Foo called\n");
    }
} CPPEmpty;

int main() {
    CPPEmpty cpp_e;
    CEmpty c_e;
    printf("sizeof(CPPEmpty): %zu\n", sizeof(cpp_e));
    cpp_e.Foo();

    printf("sizeof(CEmpty): %zu\n", sizeof(c_e));

    return 0;
}
EOF

clang++ empty_struct_test.cc -Weverything -O0 -o empty_struct_test_cpp_O0 -std=gnu++17 && ./empty_struct_test_cpp_O0
clang++ empty_struct_test.cc -Weverything -O3 -o empty_struct_test_cpp_O3 -std=gnu++17 && ./empty_struct_test_cpp_O3