[clang] [clang][HeaderSearch] Treat permission-denied include paths as non-fatal (PR #177582)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Devajith (devajithvs)

<details>
<summary>Changes</summary>

If part of the -I search path cannot be accessed (permissions), clang will throw an error, even if the header can be found in subsequent search path elements. This is counter productive as the compilation will seem to have failed due to that error, even though everyone is happy.

Based on the original patch by Axel Naumann

---
Full diff: https://github.com/llvm/llvm-project/pull/177582.diff


2 Files Affected:

- (modified) clang/lib/Lex/HeaderSearch.cpp (+2-1) 
- (added) clang/test/Preprocessor/non-accessible-include.c (+10) 


``````````diff
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 5f52d62bd36ed..689066cacc2e9 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -455,7 +455,8 @@ OptionalFileEntryRef HeaderSearch::getFileAndSuggestModule(
     std::error_code EC = llvm::errorToErrorCode(File.takeError());
     if (EC != llvm::errc::no_such_file_or_directory &&
         EC != llvm::errc::invalid_argument &&
-        EC != llvm::errc::is_a_directory && EC != llvm::errc::not_a_directory) {
+        EC != llvm::errc::is_a_directory && EC != llvm::errc::not_a_directory &&
+        EC != llvm::errc::permission_denied) {
       Diags.Report(IncludeLoc, diag::err_cannot_open_file)
           << FileName << EC.message();
     }
diff --git a/clang/test/Preprocessor/non-accessible-include.c b/clang/test/Preprocessor/non-accessible-include.c
new file mode 100644
index 0000000000000..173e6e5745037
--- /dev/null
+++ b/clang/test/Preprocessor/non-accessible-include.c
@@ -0,0 +1,10 @@
+// Needs chmod
+// UNSUPPORTED: system-windows
+//
+// RUN: chmod -R 755 %t
+// RUN: rm -rf %t && mkdir -p %t/noaccess %t/haveaccess
+// RUN: echo "int test();" > %t/haveaccess/test.h
+// RUN: chmod 000 %t/noaccess
+// RUN: %clang_cc1 -fsyntax-only -I %t/noaccess -I %t/haveaccess -verify %s
+
+#include "test.h" // expected-no-diagnostics

``````````

</details>


https://github.com/llvm/llvm-project/pull/177582