[clang] [llvm] [modules] Accept equivalent module caches from different symlink (PR #90925)

[Ellis Hoag via cfe-commits]

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@@ -839,17 +839,15 @@ static bool checkHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                      DiagnosticsEngine *Diags,
                                      const LangOptions &LangOpts,
                                      const PreprocessorOptions &PPOpts) {
-  if (LangOpts.Modules) {
-    if (SpecificModuleCachePath != ExistingModuleCachePath &&
-        !PPOpts.AllowPCHWithDifferentModulesCachePath) {
-      if (Diags)
-        Diags->Report(diag::err_pch_modulecache_mismatch)
-          << SpecificModuleCachePath << ExistingModuleCachePath;
-      return true;
-    }
-  }
-
-  return false;
+  if (!LangOpts.Modules || PPOpts.AllowPCHWithDifferentModulesCachePath ||
+      SpecificModuleCachePath == ExistingModuleCachePath ||
+      llvm::sys::fs::equivalent(SpecificModuleCachePath,
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ellishg wrote:

Thanks for the advice. I realized that this does not handle the case where both paths are equal, but do not exist. In that case, no error will be thrown. Is that acceptable? I guess this was the case before this pr.

https://github.com/llvm/llvm-project/pull/90925