https://github.com/aeubanks created
https://github.com/llvm/llvm-project/pull/71097
Canonicalizing paths on Windows leads to unexpected things like changing
drive letters. As a short term fix, do not canonicalize system headers
on Windows by default.
Fixes #70011
>From 3d519b42c350417727570ad405201cff6f1fb186 Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeuba...@google.com>
Date: Thu, 2 Nov 2023 13:00:33 -0700
Subject: [PATCH] [clang] Do not pass -canonical-system-headers on Windows by
default
Canonicalizing paths on Windows leads to unexpected things like changing
drive letters. As a short term fix, do not canonicalize system headers
on Windows by default.
Fixes #70011
---
clang/lib/Driver/ToolChains/Clang.cpp | 13 ++++++++++++-
clang/test/Driver/canonical-system-headers-win.c | 9 +++++++++
clang/test/Driver/canonical-system-headers.c | 3 +++
3 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 clang/test/Driver/canonical-system-headers-win.c
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index 79f7fba22570746..b94728f79e0a175 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -1180,8 +1180,19 @@ void Clang::AddPreprocessingOptions(Compilation &C,
const JobAction &JA,
if (ArgM->getOption().matches(options::OPT_M) ||
ArgM->getOption().matches(options::OPT_MD))
CmdArgs.push_back("-sys-header-deps");
+
+ // #70011: Canonicalization on Windows does unexpected things like change
+ // drive letters.
+ // FIXME: find and use Windows API that canonicalizes paths except for
+ // drive letter.
+#if defined(_WIN32) || defined(_WIN64)
+ bool CanonicalSystemHeadersDefault = false;
+#else
+ bool CanonicalSystemHeadersDefault = true;
+#endif
if (Args.hasFlag(options::OPT_canonical_prefixes,
- options::OPT_no_canonical_prefixes, true))
+ options::OPT_no_canonical_prefixes,
+ CanonicalSystemHeadersDefault))
CmdArgs.push_back("-canonical-system-headers");
if ((isa<PrecompileJobAction>(JA) &&
!Args.hasArg(options::OPT_fno_module_file_deps)) ||
diff --git a/clang/test/Driver/canonical-system-headers-win.c
b/clang/test/Driver/canonical-system-headers-win.c
new file mode 100644
index 000000000000000..cc3ec57ff4de614
--- /dev/null
+++ b/clang/test/Driver/canonical-system-headers-win.c
@@ -0,0 +1,9 @@
+// REQUIRES: system-windows
+// The default on Windows is false due to #70011.
+
+// RUN: %clang -MD -no-canonical-prefixes -### %s 2>&1 | FileCheck %s
--check-prefix=CHECK-NO
+// RUN: %clang -MD -canonical-prefixes -### %s 2>&1 | FileCheck %s
--check-prefix=CHECK-YES
+// RUN: %clang -MD -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-NO
+
+// CHECK-YES: "-canonical-system-headers"
+// CHECK-NO-NOT: "-canonical-system-headers"
diff --git a/clang/test/Driver/canonical-system-headers.c
b/clang/test/Driver/canonical-system-headers.c
index a7ab57521fc2249..d37b5925c73035d 100644
--- a/clang/test/Driver/canonical-system-headers.c
+++ b/clang/test/Driver/canonical-system-headers.c
@@ -1,3 +1,6 @@
+// REQUIRES: !system-windows
+// The default on Windows is false due to #70011.
+
// RUN: %clang -MD -no-canonical-prefixes -### %s 2>&1 | FileCheck %s
--check-prefix=CHECK-NO
// RUN: %clang -MD -canonical-prefixes -### %s 2>&1 | FileCheck %s
--check-prefix=CHECK-YES
// RUN: %clang -MD -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-YES
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