[clang] [llvm] [modules] Accept equivalent module caches from different symlink (PR #90925)

Ellis Hoag via llvm-commits llvm-commits at lists.llvm.org
Fri May 3 10:34:59 PDT 2024


https://github.com/ellishg updated https://github.com/llvm/llvm-project/pull/90925

>From 4760ebce0ff7725f4bb75f5107f551d867e4db6d Mon Sep 17 00:00:00 2001
From: Ellis Hoag <ellis.sparky.hoag at gmail.com>
Date: Thu, 2 May 2024 17:47:38 -0700
Subject: [PATCH 1/3] [modules] Accept equivalent module caches from different
 symlink

Use `fs::equivalent()`, which follows symlinks, to check if two module cache paths are equivalent. This prevents a PCH error when building from a different path that is a symlink of the original.

```
error: PCH was compiled with module cache path '/home/foo/blah/ModuleCache/2IBP1TNT8OR8D', but the path is currently '/data/users/foo/blah/ModuleCache/2IBP1TNT8OR8D'
1 error generated.
```
---
 clang/lib/Serialization/ASTReader.cpp | 20 +++++++++-----------
 clang/test/Modules/module-symlink.m   | 11 +++++++++++
 2 files changed, 20 insertions(+), 11 deletions(-)
 create mode 100644 clang/test/Modules/module-symlink.m

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 0ef57a3ea804ef..c20ead8b865692 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -839,17 +839,15 @@ static bool checkHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                      DiagnosticsEngine *Diags,
                                      const LangOptions &LangOpts,
                                      const PreprocessorOptions &PPOpts) {
-  if (LangOpts.Modules) {
-    if (SpecificModuleCachePath != ExistingModuleCachePath &&
-        !PPOpts.AllowPCHWithDifferentModulesCachePath) {
-      if (Diags)
-        Diags->Report(diag::err_pch_modulecache_mismatch)
-          << SpecificModuleCachePath << ExistingModuleCachePath;
-      return true;
-    }
-  }
-
-  return false;
+  if (!LangOpts.Modules || PPOpts.AllowPCHWithDifferentModulesCachePath ||
+      SpecificModuleCachePath == ExistingModuleCachePath ||
+      llvm::sys::fs::equivalent(SpecificModuleCachePath,
+                                ExistingModuleCachePath))
+    return false;
+  if (Diags)
+    Diags->Report(diag::err_pch_modulecache_mismatch)
+        << SpecificModuleCachePath << ExistingModuleCachePath;
+  return true;
 }
 
 bool PCHValidator::ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
diff --git a/clang/test/Modules/module-symlink.m b/clang/test/Modules/module-symlink.m
new file mode 100644
index 00000000000000..be447449a0e81e
--- /dev/null
+++ b/clang/test/Modules/module-symlink.m
@@ -0,0 +1,11 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules-cache-path=%t/modules -fmodules -fimplicit-module-maps -I %S/Inputs -emit-pch -o %t.pch %s -verify
+
+// RUN: ln -s %t/modules %t/modules.symlink
+// RUN: %clang_cc1 -fmodules-cache-path=%t/modules.symlink -fmodules -fimplicit-module-maps -I %S/Inputs -include-pch %t.pch %s -verify
+
+// expected-no-diagnostics
+
+ at import ignored_macros;
+
+struct Point p;

>From 490eefe98e3dd020ff3e51c7f817ec2b3d3a2663 Mon Sep 17 00:00:00 2001
From: Ellis Hoag <ellis.sparky.hoag at gmail.com>
Date: Fri, 3 May 2024 09:50:11 -0700
Subject: [PATCH 2/3] Require shell to fix windows test

---
 clang/test/Modules/module-symlink.m | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/clang/test/Modules/module-symlink.m b/clang/test/Modules/module-symlink.m
index be447449a0e81e..9a69186c5ea28f 100644
--- a/clang/test/Modules/module-symlink.m
+++ b/clang/test/Modules/module-symlink.m
@@ -1,3 +1,5 @@
+// REQUIRES: shell
+
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -fmodules-cache-path=%t/modules -fmodules -fimplicit-module-maps -I %S/Inputs -emit-pch -o %t.pch %s -verify
 

>From 6e58177107f854f42d3cdc70e796c425a1797798 Mon Sep 17 00:00:00 2001
From: Ellis Hoag <ellis.sparky.hoag at gmail.com>
Date: Fri, 3 May 2024 10:34:35 -0700
Subject: [PATCH 3/3] Use VFS to check if files are equal

---
 clang/lib/Serialization/ASTReader.cpp         | 25 +++++++++++--------
 clang/test/Modules/module-symlink.m           |  1 +
 llvm/include/llvm/Support/VirtualFileSystem.h |  4 +++
 llvm/lib/Support/VirtualFileSystem.cpp        | 10 ++++++++
 4 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index c20ead8b865692..d35c870926f96e 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -833,16 +833,18 @@ bool SimpleASTReaderListener::ReadPreprocessorOptions(
 /// against the header search options in an existing preprocessor.
 ///
 /// \param Diags If non-null, produce diagnostics for any mismatches incurred.
-static bool checkHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
+static bool checkHeaderSearchOptions(llvm::vfs::FileSystem &VFS,
                                      StringRef SpecificModuleCachePath,
                                      StringRef ExistingModuleCachePath,
                                      DiagnosticsEngine *Diags,
                                      const LangOptions &LangOpts,
                                      const PreprocessorOptions &PPOpts) {
   if (!LangOpts.Modules || PPOpts.AllowPCHWithDifferentModulesCachePath ||
-      SpecificModuleCachePath == ExistingModuleCachePath ||
-      llvm::sys::fs::equivalent(SpecificModuleCachePath,
-                                ExistingModuleCachePath))
+      SpecificModuleCachePath == ExistingModuleCachePath)
+    return false;
+  auto EqualOrErr =
+      VFS.equivalent(SpecificModuleCachePath, ExistingModuleCachePath);
+  if (EqualOrErr && *EqualOrErr)
     return false;
   if (Diags)
     Diags->Report(diag::err_pch_modulecache_mismatch)
@@ -853,10 +855,11 @@ static bool checkHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
 bool PCHValidator::ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                            StringRef SpecificModuleCachePath,
                                            bool Complain) {
-  return checkHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
-                                  PP.getHeaderSearchInfo().getModuleCachePath(),
-                                  Complain ? &Reader.Diags : nullptr,
-                                  PP.getLangOpts(), PP.getPreprocessorOpts());
+  return checkHeaderSearchOptions(
+      Reader.getFileManager().getVirtualFileSystem(), SpecificModuleCachePath,
+      PP.getHeaderSearchInfo().getModuleCachePath(),
+      Complain ? &Reader.Diags : nullptr, PP.getLangOpts(),
+      PP.getPreprocessorOpts());
 }
 
 void PCHValidator::ReadCounter(const ModuleFile &M, unsigned Value) {
@@ -5387,9 +5390,9 @@ namespace {
     bool ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                  StringRef SpecificModuleCachePath,
                                  bool Complain) override {
-      return checkHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
-                                      ExistingModuleCachePath, nullptr,
-                                      ExistingLangOpts, ExistingPPOpts);
+      return checkHeaderSearchOptions(
+          FileMgr.getVirtualFileSystem(), SpecificModuleCachePath,
+          ExistingModuleCachePath, nullptr, ExistingLangOpts, ExistingPPOpts);
     }
 
     bool ReadPreprocessorOptions(const PreprocessorOptions &PPOpts,
diff --git a/clang/test/Modules/module-symlink.m b/clang/test/Modules/module-symlink.m
index 9a69186c5ea28f..efdaf3db0dfef2 100644
--- a/clang/test/Modules/module-symlink.m
+++ b/clang/test/Modules/module-symlink.m
@@ -5,6 +5,7 @@
 
 // RUN: ln -s %t/modules %t/modules.symlink
 // RUN: %clang_cc1 -fmodules-cache-path=%t/modules.symlink -fmodules -fimplicit-module-maps -I %S/Inputs -include-pch %t.pch %s -verify
+// RUN: not %clang_cc1 -fmodules-cache-path=%t/modules.dne -fmodules -fimplicit-module-maps -I %S/Inputs -include-pch %t.pch %s -verify
 
 // expected-no-diagnostics
 
diff --git a/llvm/include/llvm/Support/VirtualFileSystem.h b/llvm/include/llvm/Support/VirtualFileSystem.h
index 0113d6b7da25d3..cea99e20eb29a5 100644
--- a/llvm/include/llvm/Support/VirtualFileSystem.h
+++ b/llvm/include/llvm/Support/VirtualFileSystem.h
@@ -320,6 +320,10 @@ class FileSystem : public llvm::ThreadSafeRefCountedBase<FileSystem>,
   ///          platform-specific error_code.
   virtual std::error_code makeAbsolute(SmallVectorImpl<char> &Path) const;
 
+  /// \returns true if \p A and \p B represent the same file, or an error or
+  /// false if they do not.
+  llvm::ErrorOr<bool> equivalent(const Twine &A, const Twine &B);
+
   enum class PrintType { Summary, Contents, RecursiveContents };
   void print(raw_ostream &OS, PrintType Type = PrintType::Contents,
              unsigned IndentLevel = 0) const {
diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index 921af30bfcde9f..f5074930718fe0 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -151,6 +151,16 @@ bool FileSystem::exists(const Twine &Path) {
   return Status && Status->exists();
 }
 
+llvm::ErrorOr<bool> FileSystem::equivalent(const Twine &A, const Twine &B) {
+  auto StatusA = status(A);
+  if (!StatusA)
+    return StatusA.getError();
+  auto StatusB = status(B);
+  if (!StatusB)
+    return StatusB.getError();
+  return StatusA->equivalent(*StatusB);
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void FileSystem::dump() const { print(dbgs(), PrintType::RecursiveContents); }
 #endif



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