Compiler/MSP430F5659: Private Member Reference of a class has a null address

Sheldon Blackshire

Part Number: MSP430F5659

Tool/software: TI C/C++ Compiler

I have a class with a private members that is a reference to an integer. When I attempt to initialize this reference in the class constructor, I discovered the address of the member is 0x000000. Has anyone seen this kind of thing before? The compiler quietly allows this and (TI v17.9.0.STS) gives no warnings or errors. Below is a screen shot that depicts a simple example that generates this problem. Note: Adding or removing the const qualifier to either the input variable or class member does not change the outcome.

over 7 years ago

0 George Mock over 7 years ago

TI__Guru**** 251180 points

This might be a problem with the debugger display. When you run through the code, with no stops, does it work as expected?

Thanks and regards,

-George

0 Sheldon Blackshire over 7 years ago in reply to George Mock

Intellectual 985 points

Dear George,

The program doesn't function properly even when I let it run.

Thanks,

0 Sheldon Blackshire over 7 years ago in reply to Sheldon Blackshire

Intellectual 985 points

Dear George,

I have been experimenting with different scenarios, and was able to make a program where the reference appears to work, but the debugger data for the reference is null. This is a different problem than the program I posed originally, but I hope the information is still useful.

0 Sheldon Blackshire over 7 years ago in reply to Sheldon Blackshire

Intellectual 985 points

Dear George,

Were you able to look into this?

Thanks,

0 George Mock over 7 years ago in reply to Sheldon Blackshire

TI__Guru**** 251180 points

Going back to the code in your first post ... This is not legal C++. I'm sorry I didn't notice sooner.

Here is the class ref. To make things more clear, I changed some names.

Line 6 is a constructor for ref. It creates a reference to arg. When this constructor completes execution, arg goes out of scope. Now you have a reference to something which does not exist. This is not legal C++.

There are various ways to fix this. Since I suspect what you show is a cutdown of your actual code, I'm not sure it makes sense to discuss how to fix this exact code. The key point is this: When a reference is created, the referent (the variable or object being referred to) must remain in scope everywhere the reference is in scope.

Thanks and regards,

-George

0 Sheldon Blackshire over 7 years ago in reply to George Mock

Intellectual 985 points

Wow, I can't believe I didn't see this either. For my example I need to pass a reference/pointer to the constructor not a value. The unfortunate thing is that the compiler and the cppcheck extension for eclipse also didn't complain.

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Compiler/MSP430F5659: Private Member Reference of a class has a null address