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I have noticed that I get error messages or I don't sometimes depending on optimization level. For example, I had a statement that tried to store a value into code space and at opt level zero, I got an error saying that it couldn't convert the lvalue. I understood this. However, at opt level 8, I got no error and in fact the 'optimizer' simply left out the offending line. Why should it do this? If it is an error, it should report it and not throw the code away.
If the line of code did nothing, the compiler, any optimizing compiler will remove it. I leave opimization on the highest level at all times.
If a line of code does nothing then certainly it would be optimized out. However, my big concern is that it was supposed to do something but there was an error in the line. I feel that the compiler should have reported the error and not simply removed the line without saying anything. I could have spent a looooong time debugging, wondering why that particular function didn't work properly.
Can you show us the error?
"If a line of code does nothing then certainly it would be optimized out. However, my big concern is that it was supposed to do something..." The compilation process is not a simple once-through operation, taking source in and spitting object out. The compiler goes through a number of phases; presumably the phase at which the optimisation decided to delete your line came before the stage which would've detected the error?! eg, i = f(x) could be perfectly syntactically correct; the fact that i happens to be in CODE space and, therefore, unwritable might not be detectable til really quite late in the code-generation process.
The statement in question that started me down this path is: *((Byte *)line.pointer)=active_thread; Hopefully, I didn't type in any new syntax errors. Anyway, the pointer element is declared as void code *pointer; so yeah it tries to store the value of active_thread into a code location. However, my question still stands. Why should the compiler simply throw it out without flagging me? Even if the process is involved, errors should be detected and reported. Seems like a bug in the compiler to me.
Your syntax is fine, so the compiler's syntax checking must give no errors. The error lies only in the fact that you have tried to write to a non-writable memory area; therefore, if the optimiser has removed that attempted write, there is nothing wrong with your code!