On gcc, the following code gives (and should give, in my opinion) -128 -128. But in VC++, it gives something else: -128 65408. Is this a bug in Visual C++? #include signed short sin_array[2]; int in_array[2]; int main(int argc, char** argv) { int p = 0; /* this signed short cast seems to cast to unsigned short */ sin_array[p++] = (signed short)in_array[p] = -128; printf("%d %d",sin_array[0],in_array[0]); return 0; }

Really. I can''t even get it to compile on VC 6. It gives a C2106 on the assignment.

Well this code would not compile for me. I got the error "error C2106: ''='' : left operand must be l-value." After i took that cast though it compiled and the output was -128 -128. Im on Visual C++ 6.0 Enterprise, i dont know which service pack, probably 5.

-SirKnight

It'll work if you do this:
sin_array[p++] = (signed short)(in_array[p] = -128);

Which makes sense ... IIRC, casts have a higher precedence than assigment operators.

~~~~~~~~~~
Martee

Edited by - Martee on July 10, 2001 10:11:20 PM

Thank you all, especially Martee, who demystified the problem. I was using VC++ version 6 SP3. I guess the moral here is use parentheses when operator precedence is not obvious.

This article:
http://support.microsoft.com/support/kb/articles/Q243/4/51.ASP

..lists all of the noncompliance issues in VC++ 6.0. If you ever have a problem that is not one of these issues, the fault is with you or your library, not the compiler. You should view this page before posting something titled "bug in C++".

sin_array[p++] = (signed short)in_array[p] = -128;

This is undefined. Therefore the results are undefined and unpredictable.