c2102 & requires L-value after usage with casting operator

[FriedrichIWM]

Hi guys,

can anybody tell me why



shmlayer_dataptr_t *ProcessImagePtr;
ProcessImagePtr = &(shmlayer_dataptr_t)ProcessImage;


is crashing in qt4.7.4 (qmake) with C2102 (but is it working with visual studio compiler for example) while



shmlayer_dataptr_t temp;
shmlayer_dataptr_t *ProcessImagePtr;
temp = (shmlayer_dataptr_t)ProcessImage;
ProcessImagePtr = &temp;


is working???

Thanks a lot!



shmlayer_dataptr_t *ProcessImagePtr;
ProcessImagePtr = &((shmlayer_dataptr_t&)ProcessImage);

is working with qt but not with visual studio c compiler

[d_stranz]

So what makes this a Qt question? Even if it was a Qt question (and not one of basic C++ syntax and usage), you haven't shown us enough code to answer the question. (Like what is "ProcessImage" for example?)

[amleto]

Firstly, if you get a compiler error, it IS NOT a crash.

Secondly, do you know the difference between lvalue and rvalue? Your working example should show you...

The compiler error states it needs an lvalue. casting like that gives an rvalue.


You should be casting pointers anyway, not instances.