How do I dump an arbitrary struct in C?

Question

I don't know which direction to go,perhaps something like reflection will help?

Answer 1

If you're using Clang 8 or newer, you can now use the built-in compiler function __builtin_dump_struct to dump a struct. It uses the information that's naturally available at compile time to generate code that pretty-prints a struct.

Example code demonstrating the function:

dumpstruct.c:

#include <stdio.h>

struct nested {
    int aa;
};

struct dumpme {
    int a;
    int b;
    struct nested n;
};

int main(void) {
    struct nested n;
    n.aa = 12;
    struct dumpme d;
    d.a = 1;
    d.b = 2;
    d.n = n;
    __builtin_dump_struct(&d, &printf);
    return 0;
}

Example compile-and-run:

$ clang dumpstruct.c -o dumpstruct
$ ./dumpstruct 
struct dumpme {
int a : 1
int b : 2
struct nested n : struct nested {
    int aa : 12
    }
}

If you're not using Clang >= 8 but you are using GCC, it's pretty easy to switch. Just install the clang-8 or clang-9 package and replace invocations of gcc with clang.