[llvm] [Support] Better error msg when cache dir can't be created. (PR #69575)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-support

Author: Tobias Hieta (tru)

<details>
<summary>Changes</summary>

On windows if you passed /lldltocache:D:\tmp to lld and you didn't have D: mounted it fail to create the cache dir D:\tmp, but the error message is pretty hard to understand:

```
c:\code\llvm\llvm-project\out\debug>bin\lld-link.exe /lldltocache:D:\tmp
hello.obj
LLVM ERROR: no such file or directory

PLEASE submit a bug report to
https://github.com/llvm/llvm-project/issues/ and include the crash
backtrace.
Exception Code: 0xC000001D
```

Which lead one of our users to report this as a crash. I have just added a bit better message so it now says:

```
c:\code\llvm\llvm-project\out\debug>bin\lld-link.exe /lldltocache:D:\tmp
hello.obj
LLVM ERROR: Can't create cache directory: D:\tmp

PLEASE submit a bug report to
https://github.com/llvm/llvm-project/issues/ and include the crash
backtrace.
```

I am not sure this is a fatal error because it's not something that really should be reported as a bug to LLVM. But at least this gives a bit more visibility on what to change.

---
Full diff: https://github.com/llvm/llvm-project/pull/69575.diff


1 Files Affected:

- (modified) llvm/lib/Support/Caching.cpp (+1-1) 


``````````diff
diff --git a/llvm/lib/Support/Caching.cpp b/llvm/lib/Support/Caching.cpp
index f20f08a865c76ff..722746e7b440390 100644
--- a/llvm/lib/Support/Caching.cpp
+++ b/llvm/lib/Support/Caching.cpp
@@ -145,7 +145,7 @@ Expected<FileCache> llvm::localCache(const Twine &CacheNameRef,
       // ensures the filesystem isn't mutated until the cache is.
       if (std::error_code EC = sys::fs::create_directories(
               CacheDirectoryPath, /*IgnoreExisting=*/true))
-        return errorCodeToError(EC);
+        return createStringError(EC, Twine("Can't create cache directory: ") + CacheDirectoryPath);
 
       // Write to a temporary to avoid race condition
       SmallString<64> TempFilenameModel;

``````````

</details>


https://github.com/llvm/llvm-project/pull/69575