[lld] [lld] check cache in loadDylib before real_path (PR #143595)

[Ellis Hoag via llvm-commits]

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@@ -225,21 +225,42 @@ std::optional<StringRef> macho::resolveDylibPath(StringRef dylibPath) {
 // especially if it's a commonly re-exported core library.
 static DenseMap<CachedHashStringRef, DylibFile *> loadedDylibs;
 
+static StringRef realPathIfDifferent(StringRef path) {
+  SmallString<128> realPathBuf;
+  std::error_code err = fs::real_path(path, realPathBuf);
+  if (err)
+    return StringRef();
+
+  StringRef realPath(realPathBuf);
+  if (realPath.ends_with(path))
+    return StringRef();
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ellishg wrote:

Is this suppose to detect symlinks? I don't think covers all cases. Imagine that in `/a/b/` you have a symlink `dir` to `/c/d/dir`. In the paths `dir` and `/c/d/dir`, the suffixes are the same, but they are different paths.

https://github.com/llvm/llvm-project/pull/143595