From 8fc7a907b93a8e9eef96e872f8f926db3ebfe9b6 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Mon, 4 May 2020 21:15:29 -0400
Subject: [PATCH] Let normalize() for posix style convert backslash to slash
 unconditionally.

Currently, normalize() for posix replaces backslashes to slashes, except
that two backslashes in sequence are kept as-is.

clang calls normalize() to convert \ to / is microsoft compat mode. This
generally works well, but a path like "c:\\foo\\bar.h" with two
backslashes doesn't work due to the exception in normalize().

These paths happen naturally on Windows hosts with e.g.
`#include __FILE__`, and them not working on other hosts makes it
more difficult to write tests for this case.

The special case has been around without justification since this code
was added in r203611 (since then moved around in r215241 r215243).  No
integration tests fail if I remove it.

Try removing the special case.

Differential Revision: https://reviews.llvm.org/D79265
---
 clang/test/Lexer/case-insensitive-include-ms.c |  6 ++++--
 llvm/lib/Support/Path.cpp                      | 12 +++---------
 llvm/unittests/Support/Path.cpp                |  2 +-
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/clang/test/Lexer/case-insensitive-include-ms.c b/clang/test/Lexer/case-insensitive-include-ms.c
index cf14d25..f7af1fe 100644
--- a/clang/test/Lexer/case-insensitive-include-ms.c
+++ b/clang/test/Lexer/case-insensitive-include-ms.c
@@ -6,15 +6,17 @@
 // RUN: %clang_cc1 -fsyntax-only -fms-compatibility %s -include %s -I %t/Output -verify
 // RUN: %clang_cc1 -fsyntax-only -fms-compatibility -fdiagnostics-parseable-fixits %s -include %s -I %t/Output 2>&1 | FileCheck %s
 
-// FIXME: Add a test with repeated backslashes once clang can handle that
-// in ms-compat mode on non-Windows hosts.
 #include "..\Output\.\case-insensitive-include.h"
 #include "..\Output\.\Case-Insensitive-Include.h" // expected-warning {{non-portable path}}
 // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:10-[[@LINE-1]]:50}:"\"..\\Output\\.\\case-insensitive-include.h\""
+#include "..\\Output\.\\Case-Insensitive-Include.h" // expected-warning {{non-portable path}}
+// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:10-[[@LINE-1]]:52}:"\"..\\\\Output\\.\\\\case-insensitive-include.h\""
 #include "..\output\.\case-insensitive-include.h" // expected-warning {{non-portable path}}
 // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:10-[[@LINE-1]]:50}:"\"..\\Output\\.\\case-insensitive-include.h\""
 
 #include "apath\..\.\case-insensitive-include.h"
 #include "apath\..\.\Case-Insensitive-Include.h" // expected-warning {{non-portable path}}
 // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:10-[[@LINE-1]]:49}:"\"apath\\..\\.\\case-insensitive-include.h\""
+#include "apath\\..\\.\\Case-Insensitive-Include.h" // expected-warning {{non-portable path}}
+// CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:10-[[@LINE-1]]:52}:"\"apath\\\\..\\\\.\\\\case-insensitive-include.h\""
 #include "APath\..\.\case-insensitive-include.h" // For the sake of efficiency, this case is not diagnosed. :-(
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 0a4d581..7756290 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -540,15 +540,9 @@ void native(SmallVectorImpl<char> &Path, Style style) {
       Path = PathHome;
     }
   } else {
-    for (auto PI = Path.begin(), PE = Path.end(); PI < PE; ++PI) {
-      if (*PI == '\\') {
-        auto PN = PI + 1;
-        if (PN < PE && *PN == '\\')
-          ++PI; // increment once, the for loop will move over the escaped slash
-        else
-          *PI = '/';
-      }
-    }
+    for (auto PI = Path.begin(), PE = Path.end(); PI < PE; ++PI)
+      if (*PI == '\\')
+        *PI = '/';
   }
 }
 
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index d80edbe..a577f1b 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -1182,7 +1182,7 @@ TEST(Support, NormalizePath) {
   Tests.emplace_back("a", "a", "a");
   Tests.emplace_back("a/b", "a\\b", "a/b");
   Tests.emplace_back("a\\b", "a\\b", "a/b");
-  Tests.emplace_back("a\\\\b", "a\\\\b", "a\\\\b");
+  Tests.emplace_back("a\\\\b", "a\\\\b", "a//b");
   Tests.emplace_back("\\a", "\\a", "/a");
   Tests.emplace_back("a\\", "a\\", "a/");
   Tests.emplace_back("a\\t", "a\\t", "a/t");
-- 
2.7.4