Increment int in structure

**fulumbler** · 03-06-2017

Hey all!
I am quite a beginner and have a very beginner-ish question.

I have a structure containing an int value.
I also have a pointer to an instance of that structure and want to increase the int value.

My code:

Code:

pointer->value = pointer->value + 1;

or

Code:

pointer->value++;

crashes the second time I execute it.
Always.

I am using the same code in another function, with the same pointer, there it works.
The pointer value is not null, I know that for sure.
The int value is 1 at the time of the crash.

Is there a general reason why such a simple command could crash?
If not I'll keep digging, but that thing has kept me occupied for two days now and I'm feeling slightly ridiculous.

Thanks for any help and have a nice day!

**algorism** · 03-06-2017

There is something else going on. You need to post your code.

**fulumbler** · 03-08-2017

Originally Posted by algorism

There is something else going on. You need to post your code.

You were absolutely right, thank you algorism!
I'm afraid it might have something to do with the RAM limit and memory not being freed fast enough.

I might post a related question if I can't resolve the issue myself, I should do it then in a new thread I guess, since the title doesn't really fit anymore.

Thank you for your answer!

**algorism** · 03-08-2017

Memory corruption is an insidious error. The effects can show up far away from the cause. Just because the pointer is not NULL doesn't mean it's valid. It's probably being overwritten at some point (with a non-null value).

**Terrance** · 03-09-2017

Originally Posted by fulumbler

You were absolutely right, thank you algorism!
I'm afraid it might have something to do with the RAM limit and memory not being freed fast enough.

I might post a related question if I can't resolve the issue myself, I should do it then in a new thread I guess, since the title doesn't really fit anymore.

Thank you for your answer!

This from the book "The C Programming Language" by Kernighan and Ritchie. Page 120 - "A structure declaration that is not followed by a list of variables allocates no storage." Maybe this has something to do with the problem? You aren't allocating memory correctly, therefore the pointer is pointing to nothing, and this causes your program to crash.

**GReaper** · 03-09-2017

Originally Posted by Terrance

This from the book "The C Programming Language" by Kernighan and Ritchie. Page 120 - "A structure declaration that is not followed by a list of variables allocates no storage."

I think you have completely misunderstood that statement. It doesn't say that a struct variable, if not explicitly defined, doesn't have space allocated for it. It says that if you don't follow a structure declaration/definition with a list of variables, it doesn't allocate any space and acts as a template for future use( the way most of us use it ).

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