If I were the author, I would skip the part about using the compiler explorer and reading the assembly. When I write C code, I need to satisfy the rules of the C language. Unless I’m debugging the compiler or dealing with performance issues, my experience is that reading the generated assembler and understanding it is usually a slow way of debugging. The author eventually did compile with -fsanitize=undefined but I would honestly do that first. It prints a nice error message about the exact issue as the author has shown.
Yikes. I think this article undersells the point somewhat. This line of code undermines the type system by spraying -1's into an array of structs, so the only surprise to me is that it took this long to break.
> Option 1) seemed like the easiest one, but it also felt a bit like kicking the can down the road – plus, it introduced the question of which standard to use.
Arguably, that's the sanest one: you can't expect the old C code to follow the rules of the new versions of the language. In a better world, each source file would start with something like
#pragma lang_ver stdc89
On the topic of the article, yeah, sticking anything other than 0 or 1 into C99 bool type is UB. Use ints.
> Ah-ha! The generated instructions were ever so slightly different. This would be great news, if it wasn't for me forgetting about one little detail: I have zero knowledge of x86 assembly.
Lol'd at this. I've been there: "ah hah! I found you. hrm, now what does this mean..."
TFA makes me thankful my work doesn't involve C / C++. Learning it earlier in life was enough.