microsoft / microsoft/STL

<streambuf>: basic_streambuf doesn't support 64-bit properly

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bug vNext
Dominant language
C++
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Description

std::basic_streambuf doesn't support 64-bit properly, because it holds the counters in 32-bit ints:

https://github.com/microsoft/STL/blob/b61483432979aafb6b89b245fb8e82eee7aee32f/stl/inc/streambuf#L392-L395

Then e.g. in std::basic_streambuf::setg(...) you have:

https://github.com/microsoft/STL/blob/b61483432979aafb6b89b245fb8e82eee7aee32f/stl/inc/streambuf#L210

and forcing a cast to int prevents from using with a memory range bigger than ~2GB (even on Win64 builds).

Also tracked by DevCom-102668, DevCom-290124, DevCom-320893, DevCom-859581, and Microsoft-internal VSO-485517 / AB#485517.

vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.

Contributor guide

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with stl/inc/streambuf at the linked counter definitions and basic_streambuf::setg(...), then read #169 for the vNext and binary-compatibility constraints. The issue is ready only when the vNext branch is available; done means 64-bit memory ranges are supported without the current 32-bit limitations and the relevant compatibility requirements are met.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
devtools
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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