MSBuild OOM crash fix #892
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This should help avoid OOMs thrown when operating on repos with very large git database files. More importantly, this fixes a leak where `SafeMemoryMappedViewHandle.ReleasePointer` was not getting called in `GitPackIndexMappedReader`. Without calling this, the native memory just leaks until the msbuild.exe process crashes.
AArnott
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Feb 14, 2023
We had been mapping only parts of the index into memory, and shifting the mapped window with each call to `GetSpan`. The problem was the caller would use `GetSpan` more than once, and hold each result such that it had a pointer/span into both windows when only one existed at any given point. This fixes a regression made in #892 (395dfa7). In that change, I tried to reduce the mapped file from the whole file to just a window. That was as part of fixing an `OutOfMemoryException`, but ultimately I believe that was due to a memory leak, which that PR also fixed. So in this change I keep the memory leak fix (by releasing the acquired pointer) but revert the smaller, moving window code change.
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Fixes a couple possible reasons for running out of memory during a build.