Turbo C++ and GCC (using codeblocks on windows) evaluate the same ternary expression differently

Question

I have this expression

(*p % 3 != 0) ? *p = (*p) + 1 : *p = (*p) + 2;

In Turbo C++ it evaluates to 14 if *p is 11 and to 35 if *p is 33

In GCC (Windows) it evaluates to 12 and 35 respectively which is what is expected

It works fine when parenthesized to the following format:

(*p % 3 != 0) ? (*p = (*p) + 1) : (*p = (*p) + 2); 

Is there any explanation for this difference? I'm guessing it comes down to differences in the precedence order used by the compilers but cannot pinpoint the root cause

Answer 1

The ternary conditional operator is different in C and in C++. The expression a ? b : c = d is parsed...

• as (a ? b : c) = d in C, and

• as a ? b : (c = d) in C++.