[all-commits] [llvm/llvm-project] e6f5e4: [Windows][Support] Add helper to expand short 8.3 ...

[Ben Dunbobbin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e6f5e4910df519a3f14e0db86d24abe8fd25082b
      https://github.com/llvm/llvm-project/commit/e6f5e4910df519a3f14e0db86d24abe8fd25082b
  Author: Ben Dunbobbin <Ben.Dunbobbin at sony.com>
  Date:   2026-02-10 (Tue, 10 Feb 2026)

  Changed paths:
    M llvm/include/llvm/Support/Windows/WindowsSupport.h
    M llvm/lib/Support/Windows/Path.inc
    M llvm/unittests/Support/Path.cpp

  Log Message:
  -----------
  [Windows][Support] Add helper to expand short 8.3 form paths (#178480)

Windows supports short 8.3 form filenames (for example,
`compile_commands.json` -> `COMPIL~1.JSO`) for legacy reasons. See:
https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#short-vs-long-names

Such paths are not unusual because, on Windows, the system temporary
directory is commonly derived from the `TMP`/`TEMP` environment
variables. For historical compatibility reasons, these variables are
often set to short 8.3 form paths on systems where user names exceed
eight characters.

Introduce `windows::makeLongFormPath()` to convert paths to their long
form by expanding any 8.3 components via `GetLongPathNameW`.

As part of this change:
- Extended-length path prefix handling is centralized by adding
`stripExtendedPrefix()` and reusing it in `realPathFromHandle()`.
- `widenPath()` is cleaned up to use shared prefix constants.

This was split out from #178303 at the request of the codeowner so that
the Windows support parts can be reviewed separately.



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