[Support][Windows] Use the original path if GetFinalPathNameByHandleW() failed

[slydiman]

The commit f11b056 (#76304) breaks clang and other tools if they are used from a RAMDrive. GetFinalPathNameByHandleW() may return 0 and GetLastError 0x28. This patch fixes that issue. Note real_path() uses openFileForRead() but it reports the error only if failed to open a file. Getting RealPath is optional functionality.

BTW, sys::fs::real_path() resolves not only symlinks, but also network drives and virtual drives created by the subst tool. It may break an automation. It is better to detect symlinks and resolve only symlinks.

[llvmbot]

@llvm/pr-subscribers-llvm-support

@llvm/pr-subscribers-platform-windows

Author: Dmitry Vasilyev (slydiman)

Changes

The commit f11b056 (#76304) breaks clang and other tools if they are used from a RAMDrive. GetFinalPathNameByHandleW() may return 0 and GetLastError 0x28. This patch fixes that issue. Note real_path() uses openFileForRead() but it reports the error only if failed to open a file. Getting RealPath is optional functionality.

BTW, sys::fs::real_path() resolves not only symlinks, but also network drives and virtual drives created by the subst tool. It may break an automation. It is better to detect symlinks and resolve only symlinks.

---

Full diff: https://github.com/llvm/llvm-project/pull/87749.diff

1 Files Affected:

• (modified) llvm/lib/Support/Windows/Path.inc (+3-1)

diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 854d531ab371fc..4f0336a85daaa5 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -157,7 +157,9 @@ std::string getMainExecutable(const char *argv0, void *MainExecAddr) {
 
   SmallString<256> RealPath;
   sys::fs::real_path(PathNameUTF8, RealPath);
-  return std::string(RealPath);
+  if (RealPath.size())
+    return std::string(RealPath);
+  return std::string(PathNameUTF8.data());
 }
 
 UniqueID file_status::getUniqueID() const {

[mstorsjo]

This change looks reasonable to me, but I want to loop in @aganea before landing it.

[aganea]

LGTM, thanks for the fix!

If you want to avoid resolution with network drives or virtuals substs, you can also use clang … -no-canonical-paths I think, that should avoid calling this function.