Please help with a heapalloc problem

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C

memory

My program is written in regular C in Visual Studio 2017 and runs on Windows 10.

It reads binary files into memory and extracts out information. If I process a large number (over 100) of really large files (50-75MB) I get a HeapAlloc error. I'm doing a HeapAlloc, processing the file, and then doing HeapFree. For some reason the heap keeps increasing in size until it hits the limit for 32bit applications.

I was under the impression that if I did a HeapFree, the next HeapAlloc would reuse the memory already used by the heap. It appears that isn't the case.

What should I be doing differently?

What I have tried:

// do this once at the start
hHeap = GetProcessHeap();

// the following once per file

hFile = CreateFile(lpszLibraryName,GENERIC_READ, FILE_SHARE_READ, NULL,						 
                    OPEN_EXISTING, 0, NULL);

dwFileSize = GetFileSize(hFile, &dwSizeHigh);

lpHeapData = HeapAlloc(hHeap, HEAP_ZERO_MEMORY, dwFileSize + 1);

ReadFile(hFile, lpHeapData, dwFileSize, &dwBytesRead, NULL);

... process the file data ...

HeapFree(hHeap, 0, lpHeapData);

CloseHandle(hFile);