Identify if a file is a system header by its path

Author: Jinjie-Huang

clang/lib/Lex/HeaderSearch.cpp

@@ -887,9 +887,11 @@ void HeaderSearch::DiagnoseHeaderShadowing(
     ArrayRef<std::pair<OptionalFileEntryRef, DirectoryEntryRef>> Includers,
     bool isAngled, int IncluderLoopIndex, ConstSearchDirIterator MainLoopIt) {
 
-  if (Diags.isIgnored(diag::warn_header_shadowing, IncludeLoc) || isAngled ||
-      DiagnosedShadowing)
+  if (Diags.isIgnored(diag::warn_header_shadowing, IncludeLoc) ||
+      DiagnosedShadowing || (getFileInfo(*FE).DirInfo != SrcMgr::C_User)) {
+    DiagnosedShadowing = true;
     return;
+  }
 
   DiagnosedShadowing = true;
 

clang/test/Preprocessor/header-shadowing.c

@@ -3,24 +3,24 @@
 
 /// Check that:
 /// - Quoted includes ("...") trigger the diagnostic.
-/// - Angled includes (<...>) are ignored.
+/// - System headers are ignored.
 /// - #include_next does not cause a duplicate warning.
 // RUN: %clang_cc1 -Wshadow-header -Eonly %t/main.c -I %t/include1 -I %t/include2 \
 // RUN: -isystem %t/system1 -isystem %t/system2 2>&1 | FileCheck %s --check-prefix=SHADOWING
 
-// SHADOWING: {{.*}} warning: multiple candidates for header 'header.h' found; directory '{{.*}}include1' chosen, ignoring '{{.*}}include2' and others [-Wshadow-header]
+// SHADOWING: {{.*}} warning: multiple candidates for header 'header.h' found; directory '{{.*}}/include1' chosen, ignoring '{{.*}}/include2' and others [-Wshadow-header]
 // SHADOWING: warning: include1/header.h included!
-// SHADOWING-NOT: {{.*}} warning: multiple candidates for header 'header.h' found; directory '{{.*}}include2' chosen, ignoring '{{.*}}include1' and others [-Wshadow-header]
+// SHADOWING-NOT: {{.*}} warning: multiple candidates for header 'header.h' found; directory '{{.*}}/include2' chosen, ignoring '{{.*}}/include1' and others [-Wshadow-header]
 // SHADOWING: warning: include2/header.h included!
-// SHADOWING-NOT: {{.*}} warning: multiple candidates for header 'stdio.h' found; directory '{{.*}}system1' chosen, ignoring '{{.*}}system2' and others [-Wshadow-header]
+// SHADOWING-NOT: {{.*}} warning: multiple candidates for header 'stdio.h' found; directory '{{.*}}/system1' chosen, ignoring '{{.*}}/system2' and others [-Wshadow-header]
 // SHADOWING: warning: system1/stdio.h included!
 
 /// Check that the diagnostic is only performed once in MSVC compatibility mode.
-// RUN: %clang_cc1 -fms-compatibility -Wshadow-header -Eonly %t/t.c -I %t -I %t/foo -I %t/foo/bar 2>&1 | FileCheck %s --check-prefix=SHADOWING-MS
+// RUN: %clang_cc1 -fms-compatibility -Wshadow-header -Eonly %t/t.c 2>&1 | FileCheck %s --check-prefix=SHADOWING-MS
 
-// SHADOWING-MS: {{.*}} warning: multiple candidates for header 't3.h' found; directory '{{.*}}foo' chosen, ignoring '{{.*}}' and others [-Wshadow-header]
+// SHADOWING-MS: {{.*}} warning: multiple candidates for header 't3.h' found; directory '{{.*}}/foo' chosen, ignoring '{{.*}}' and others [-Wshadow-header]
+// SHADOWING-MS-NOT: {{.*}} warning: multiple candidates for header 't3.h' found; directory '{{.*}}' chosen, ignoring '{{.*}}/foo' and others [-Wshadow-header]
 // SHADOWING-MS: warning: Found foo/t3.h.
-// SHADOWING-MS-NOT: {{.*}} warning: multiple candidates for header 't3.h' found; directory '{{.*}}foo' chosen, ignoring '{{.*}}' and others [-Wshadow-header]
 
 //--- main.c
 #include "header.h"