Allocate / free memory with Visual Studio C++

Question

Allocate / free memory with Visual Studio C++

Ollivier TARAMASCO 0

I have a very simple program

int main(void)

{ double* myVect = new double[10000000];

wait(2); // wait for 2 seconds

delete[] myVect;

wait(2);

return 0;

}

I execute this program in Debug mode, put a breakpoint on "return 0" and look at the diagnostic tools (sorry I've a French version of Visual Studio 2022).

OutilsDignostic

Why the memory isn't released?

Viorel 125.7K Reputation points

2025-06-29T10:07:06.38+00:00

Maybe this picture (and 147 Mo) does not correspond to the shown code.
RLWA32 51,456 Reputation points

2025-06-29T10:36:23.3966667+00:00

@Viorel, Notwithstanding the memory amounts shown initially the diagnostics displayed to me looked very similar to the Questioner's image. I suspect its not indicative of a memory problem but relates to timing and presentation for the diagnostic session graph.
Darran Rowe 2,531 Reputation points

2025-06-30T00:30:14.6533333+00:00

10,000,000 doubles should only be around 87MiB, not 147. There is also the problem that not knowing the project type doesn't help, since Visual Studio can report interesting things in the memory that it shows.

To give one example, this is the memory shown for an almost blank WinUI 3 application compared to what is reported in Task Manager.

What is reported in Visual Studio seems to be a mix of the working set and dedicated GPU memory this means that the memory shown can be misleading.

But explicitly using the Sleep function, I don't really see any issue.

2 answers

Your answer

Viorel 125.7K Reputation points

2025-06-29T10:07:06.38+00:00

Maybe this picture (and 147 Mo) does not correspond to the shown code.
RLWA32 51,456 Reputation points

2025-06-29T10:36:23.3966667+00:00

@Viorel, Notwithstanding the memory amounts shown initially the diagnostics displayed to me looked very similar to the Questioner's image. I suspect its not indicative of a memory problem but relates to timing and presentation for the diagnostic session graph.
Darran Rowe 2,531 Reputation points

2025-06-30T00:30:14.6533333+00:00

10,000,000 doubles should only be around 87MiB, not 147. There is also the problem that not knowing the project type doesn't help, since Visual Studio can report interesting things in the memory that it shows.

To give one example, this is the memory shown for an almost blank WinUI 3 application compared to what is reported in Task Manager.

What is reported in Visual Studio seems to be a mix of the working set and dedicated GPU memory this means that the memory shown can be misleading.

But explicitly using the Sleep function, I don't really see any issue.

Answer 1

RLWA32 51,456

I increased the interval between allocation, free and termination to make memory changes more visible in the diagnostic session. I also took snapshots before allocation, before free and after free. This is what was displayed.

Memory

So the memory is being freed when delete is called but the display you are looking at doesn't clearly reflect the activity due to the short lag between free and program termination.

Answer 2

Bruce (SqlWork.com) 82,061 Volunteer Moderator

when you ask for an allocation that is larger than the heap has free memory, it requests more process memory form the O/S, thus going the process memory size. when you release memory to the heap (delete), the deleted memory is marked as free, but not returned to the O/S, so the process memory size does not change. You do have lots of free heap memory.

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Allocate / free memory with Visual Studio C++

2 answers

Your answer