Running lit tests on Windows can fail because its use of
`os.path.realpath` expands substitute drives, which are used to keep
paths short and avoid hitting MAX_PATH limitations.
Changes lit logic to:
Use `os.path.abspath` on Windows, where `MAX_PATH` is a concern that we
can work around using substitute drives, which `os.path.realpath` would
resolve.
Use `os.path.realpath` on Unix, where the current directory always has
symlinks resolved, so it is impossible to preserve symlinks in the
presence of relative paths, and so we must make sure that all code paths
use real paths.
Also updates clang's `FileManager::getCanonicalName` and `ExtractAPI`
code to avoid resolving substitute drives (i.e. resolving to a path
under a different root).
How tested: built with `-DLLVM_ENABLE_PROJECTS=clang` and built `check-all` on both Windows
Differential Revision: https://reviews.llvm.org/D154130
Reviewed By: @benlangmuir
Patch by Tristan Labelle <tristan@thebrowser.company>!
This reverts commit c1cf459cbd79cc7d6ca834390649fb9185a4b237.
Reverting to permit time to explore the underlying issue. This change
regressed the clang-PPC64-AIX and m68k-linux-cross builders.
Differential Revision: https://reviews.llvm.org/D153138
Reviewed By: compnerd
lit.py uses os.path.realpath on file paths. Somewhere between Python 3.7
and 3.9, os.path.realpath was updated to resolve substitute drives on
Windows (subst S: C:\Long\Path\To\My\Code). This is a problem because it
prevents using substitute drives to work around MAX_PATH path length
limitations on Windows.
We run into this while building & testing, the Swift compiler on
Windows, which uses a substitute drive in CI to shorten the workspace
directory. cmake builds without resolving the substitute drive and can
apply its logic to avoid output files exceeding MAX_PATH. However, when
running tests, lit.py's use of os.path.realpath will resolve the
substitute drive (with newer Python versions), resulting in some paths
being longer than MAX_PATH, which cause all kinds of failures (for
example rd in tests fails, or link.exe fails, etc).
How tested: Ran check-all, and lit tests, saw no failures
```
> ninja -C build check-all
Testing Time: 262.63s
Skipped : 24
Unsupported : 2074
Passed : 51812
Expectedly Failed: 167
> python utils\lit\lit.py --path ..\build\bin utils\lit\tests
Testing Time: 12.17s
Unsupported: 6
Passed : 47
```
Patch by Tristan Labelle!
Differential Revision: https://reviews.llvm.org/D152709
Reviewed By: rnk, compnerd
