Which stage of the compiler detects the following errornous program?

Question

I'm having some trouble in understanding the differences between different errors in the complier phases, for instance this program:

int main()
{
      int x = 5;
      int x = 6;
}

My guess is that this would fail in the semantic analysis phase, but I'm not that certain (is it possible that it would fail in the lexical analysis phase as a duplicate token for (int x) would be generated?)

Appreciate your help.

Answer 1

You're right, this program is both lexically and syntactically correct but not semanticaly, assuming that the language you describe here is standard C or C++.

C/C++ does not allow redefinition of variables - that's semantics. If your language allowed variable redefinitions, it would be a semantically correct program.