[clang] [llvm] Make sanitizer special case list slash-agnostic (PR #149886)

[Devon Loehr via llvm-commits]

https://github.com/DKLoehr created https://github.com/llvm/llvm-project/pull/149886

This changes the glob matcher for the sanitizer special case format so that it treats `/` as matching both forward and back slashes.

When dealing with cross-compiles or build systems that don't normalize slashes, it's possible to run into file paths with inconsistent slashiness, e.g. `../..\v8/include\v8-internal.h` when [building chromium](https://g-issues.chromium.org/issues/425364464).

We can match this using the current syntax using this ugly kludge: `src:*{/,\\}v8{/,\\}*`. However, since the format is explicitly for listing file paths, it makes sense to treat `/` as denoting a path separator rather than a literal forward slash. This allows us to write the much more natural form `src:*/v8/*` and have it work on any platform.

This is technically a behavior change, but it seems very unlikely to come up in practice. It will only make a difference if a user has a system where both `a/b` and `a\b` exist, are different files, _and_ they only want to capture the first of them. Even in the worst case, they can still regain the previous behavior by escaping the slash character in their pattern: `src:a\/b`.

>From 40745a6b7caf7fae4a84b2e819ba4e45d6df0112 Mon Sep 17 00:00:00 2001
From: Devon Loehr <dloehr at google.com>
Date: Mon, 21 Jul 2025 19:07:23 +0000
Subject: [PATCH] Make special case matcher slash-agnostic

---
 clang/docs/SanitizerSpecialCaseList.rst  |  1 +
 clang/unittests/Basic/DiagnosticTest.cpp | 23 +++++++++++++++++++++++
 llvm/docs/ReleaseNotes.md                |  4 ++++
 llvm/include/llvm/Support/GlobPattern.h  |  1 +
 llvm/lib/Support/GlobPattern.cpp         |  4 ++++
 5 files changed, 33 insertions(+)

diff --git a/clang/docs/SanitizerSpecialCaseList.rst b/clang/docs/SanitizerSpecialCaseList.rst
index 194f2fc5a7825..3aea40ce0715d 100644
--- a/clang/docs/SanitizerSpecialCaseList.rst
+++ b/clang/docs/SanitizerSpecialCaseList.rst
@@ -174,6 +174,7 @@ tool-specific docs.
     # Lines starting with # are ignored.
     # Turn off checks for the source file
     # Entries without sections are placed into [*] and apply to all sanitizers
+    # "/" matches both windows and unix path separators ("/" and "\")
     src:path/to/source/file.c
     src:*/source/file.c
     # Turn off checks for this main file, including files included by it.
diff --git a/clang/unittests/Basic/DiagnosticTest.cpp b/clang/unittests/Basic/DiagnosticTest.cpp
index b0a034e9af1cd..3ab3cc918f5dc 100644
--- a/clang/unittests/Basic/DiagnosticTest.cpp
+++ b/clang/unittests/Basic/DiagnosticTest.cpp
@@ -360,4 +360,27 @@ TEST_F(SuppressionMappingTest, ParsingRespectsOtherWarningOpts) {
   clang::ProcessWarningOptions(Diags, Diags.getDiagnosticOptions(), *FS);
   EXPECT_THAT(diags(), IsEmpty());
 }
+
+TEST_F(SuppressionMappingTest, ForwardSlashMatchesBothDirections) {
+  llvm::StringLiteral SuppressionMappingFile = R"(
+  [unused]
+  src:*clang/*
+  src:*clang/lib/Sema/*=emit
+  src:*clang/lib\\Sema/foo*)";
+  Diags.getDiagnosticOptions().DiagnosticSuppressionMappingsFile = "foo.txt";
+  FS->addFile("foo.txt", /*ModificationTime=*/{},
+              llvm::MemoryBuffer::getMemBuffer(SuppressionMappingFile));
+  clang::ProcessWarningOptions(Diags, Diags.getDiagnosticOptions(), *FS);
+  EXPECT_THAT(diags(), IsEmpty());
+
+  EXPECT_TRUE(Diags.isSuppressedViaMapping(
+      diag::warn_unused_function, locForFile(R"(clang/lib/Basic/foo.h)")));
+  EXPECT_FALSE(Diags.isSuppressedViaMapping(
+      diag::warn_unused_function, locForFile(R"(clang/lib/Sema\bar.h)")));
+  EXPECT_TRUE(Diags.isSuppressedViaMapping(
+      diag::warn_unused_function, locForFile(R"(clang\lib\Sema/foo.h)")));
+  // The third pattern requires a literal backslash before Sema
+  EXPECT_FALSE(Diags.isSuppressedViaMapping(
+      diag::warn_unused_function, locForFile(R"(clang/lib/Sema/foo.h)")));
+}
 } // namespace
diff --git a/llvm/docs/ReleaseNotes.md b/llvm/docs/ReleaseNotes.md
index bb1f88e8480f1..8a883b7329343 100644
--- a/llvm/docs/ReleaseNotes.md
+++ b/llvm/docs/ReleaseNotes.md
@@ -338,6 +338,10 @@ Changes to BOLT
 Changes to Sanitizers
 ---------------------
 
+* The [sanitizer special case list format](https://clang.llvm.org/docs/SanitizerSpecialCaseList.html#format)
+  now treats forward slashes as either a forward or a backslash, to handle
+  paths with mixed unix and window styles.
+
 Other Changes
 -------------
 
diff --git a/llvm/include/llvm/Support/GlobPattern.h b/llvm/include/llvm/Support/GlobPattern.h
index 62ed4a0f23fd9..af92c63331282 100644
--- a/llvm/include/llvm/Support/GlobPattern.h
+++ b/llvm/include/llvm/Support/GlobPattern.h
@@ -35,6 +35,7 @@ namespace llvm {
 ///   expansions are not supported. If \p MaxSubPatterns is empty then
 ///   brace expansions are not supported and characters `{,}` are treated as
 ///   literals.
+/// * `/` matches both unix and windows path separators: `/` and `\`.
 /// * `\` escapes the next character so it is treated as a literal.
 ///
 /// Some known edge cases are:
diff --git a/llvm/lib/Support/GlobPattern.cpp b/llvm/lib/Support/GlobPattern.cpp
index 7004adf461a0c..26b3724863ee8 100644
--- a/llvm/lib/Support/GlobPattern.cpp
+++ b/llvm/lib/Support/GlobPattern.cpp
@@ -231,6 +231,10 @@ bool GlobPattern::SubGlobPattern::match(StringRef Str) const {
         ++S;
         continue;
       }
+    } else if (*P == '/' && (*S == '/' || *S == '\\')) {
+      ++P;
+      ++S;
+      continue;
     } else if (*P == *S || *P == '?') {
       ++P;
       ++S;