[Frontend] Fix an issue where a quoted search path is incorrectly

removed as a duplicate header search path

The commit r126167 started passing the First index into RemoveDuplicates, but
forgot to update 0 to First in the loop that looks for the duplicate. This
resulted in a bug where an -iquoted search path was incorrectly removed if you
passed in the same path into -iquote and more than one time into -isystem.

rdar://23991350

Differential Revision: https://reviews.llvm.org/D27298


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288491 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Frontend/InitHeaderSearch.cpp

@@ -526,7 +526,7 @@ static unsigned RemoveDuplicates(std::vector<DirectoryLookup> &SearchList,
     if (CurEntry.getDirCharacteristic() != SrcMgr::C_User) {
       // Find the dir that this is the same of.
       unsigned FirstDir;
-      for (FirstDir = 0; ; ++FirstDir) {
+      for (FirstDir = First;; ++FirstDir) {
         assert(FirstDir != i && "Didn't find dupe?");
 
         const DirectoryLookup &SearchEntry = SearchList[FirstDir];

test/Frontend/include-duplicate-removal.c

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -v -I%S/Inputs -iquote %S/Inputs/SystemHeaderPrefix -isystem %S/Inputs/SystemHeaderPrefix -isystem %S/Inputs/SystemHeaderPrefix %s 2>&1 | FileCheck %s
+
+#include <test.h>
+
+// CHECK: ignoring duplicate directory
+// CHECK-SAME: Inputs/SystemHeaderPrefix"{{$}}
+
+// CHECK:      #include "..."
+// CHECK-NEXT: {{.*}}Inputs/SystemHeaderPrefix{{$}}
+// CHECK-NEXT: #include <...>
+// CHECK-NEXT: {{.*}}Inputs{{$}}
+// CHECK-NEXT: {{.*}}Inputs/SystemHeaderPrefix{{$}}