[llvm] [CAS] Give Windows file mappings names to better ensure same mappings are used (PR #190692)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-support

Author: Hiroshi Yamauchi (hjyamauchi)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/190692.diff


4 Files Affected:

- (modified) llvm/include/llvm/Support/FileSystem.h (+3-2) 
- (modified) llvm/lib/CAS/MappedFileRegionArena.cpp (+10-1) 
- (modified) llvm/lib/Support/Unix/Path.inc (+4-3) 
- (modified) llvm/lib/Support/Windows/Path.inc (+11-4) 


``````````diff
diff --git a/llvm/include/llvm/Support/FileSystem.h b/llvm/include/llvm/Support/FileSystem.h
index 38b801dffeb29..320daf56fd1f6 100644
--- a/llvm/include/llvm/Support/FileSystem.h
+++ b/llvm/include/llvm/Support/FileSystem.h
@@ -1335,7 +1335,7 @@ class mapped_file_region {
   LLVM_ABI void willNeedImpl();
 
   LLVM_ABI std::error_code init(sys::fs::file_t FD, uint64_t Offset,
-                                mapmode Mode);
+                                mapmode Mode, const char* Name);
 
 public:
   mapped_file_region() = default;
@@ -1351,7 +1351,8 @@ class mapped_file_region {
 
   /// \param fd An open file descriptor to map. Does not take ownership of fd.
   LLVM_ABI mapped_file_region(sys::fs::file_t fd, mapmode mode, size_t length,
-                              uint64_t offset, std::error_code &ec);
+                              uint64_t offset, std::error_code &ec,
+                              const char* name = nullptr);
 
   ~mapped_file_region() { unmapImpl(); }
 
diff --git a/llvm/lib/CAS/MappedFileRegionArena.cpp b/llvm/lib/CAS/MappedFileRegionArena.cpp
index 2dae3f2d05116..5712edaa629b0 100644
--- a/llvm/lib/CAS/MappedFileRegionArena.cpp
+++ b/llvm/lib/CAS/MappedFileRegionArena.cpp
@@ -252,8 +252,17 @@ Expected<MappedFileRegionArena> MappedFileRegionArena::create(
   // Create the mapped region.
   {
     std::error_code EC;
+    const char *Name = nullptr;
+#ifdef _WIN32
+    // Give the file mapping a name to ensure the same mappings are
+    // shared across processes.
+    std::string MapName = Result.Path;
+    std::replace(MapName.begin(), MapName.end(), '\\', '/');
+    MapName = "Local\\" + MapName;
+    Name = MapName.c_str();
+#endif
     sys::fs::mapped_file_region Map(
-        File, sys::fs::mapped_file_region::readwrite, Capacity, 0, EC);
+        File, sys::fs::mapped_file_region::readwrite, Capacity, 0, EC, Name);
     if (EC)
       return createFileError(Result.Path, EC);
     Result.Region = std::move(Map);
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 057276f9b7eb2..aaa11a7b5e9f1 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -861,7 +861,7 @@ std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,
 }
 
 std::error_code mapped_file_region::init(int FD, uint64_t Offset,
-                                         mapmode Mode) {
+                                         mapmode Mode, const char* Name) {
   assert(Size != 0);
 
   int flags = (Mode == readwrite) ? MAP_SHARED : MAP_PRIVATE;
@@ -896,12 +896,13 @@ std::error_code mapped_file_region::init(int FD, uint64_t Offset,
 }
 
 mapped_file_region::mapped_file_region(int fd, mapmode mode, size_t length,
-                                       uint64_t offset, std::error_code &ec)
+                                       uint64_t offset, std::error_code &ec,
+                                       const char* name)
     : Size(length), Mode(mode) {
   sandbox::violationIfEnabled();
 
   (void)Mode;
-  ec = init(fd, offset, mode);
+  ec = init(fd, offset, mode, name);
   if (ec)
     copyFrom(mapped_file_region());
 }
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 48825a2de4993..5f54744fd2046 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -1030,7 +1030,8 @@ std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,
 }
 
 std::error_code mapped_file_region::init(sys::fs::file_t OrigFileHandle,
-                                         uint64_t Offset, mapmode Mode) {
+                                         uint64_t Offset, mapmode Mode,
+                                         const char* Name) {
   this->Mode = Mode;
   if (OrigFileHandle == INVALID_HANDLE_VALUE)
     return make_error_code(errc::bad_file_descriptor);
@@ -1048,8 +1049,14 @@ std::error_code mapped_file_region::init(sys::fs::file_t OrigFileHandle,
     break;
   }
 
+  SmallVector<wchar_t, 128> NameUTF16;
+  if (Name)
+    if (std::error_code EC = UTF8ToUTF16(Name, NameUTF16))
+      return EC;
+
   HANDLE FileMappingHandle = ::CreateFileMappingW(OrigFileHandle, 0, flprotect,
-                                                  Hi_32(Size), Lo_32(Size), 0);
+                                                  Hi_32(Size), Lo_32(Size),
+                                                  Name ? c_str(NameUTF16) : 0);
   if (FileMappingHandle == NULL) {
     std::error_code ec = mapWindowsError(GetLastError());
     return ec;
@@ -1106,11 +1113,11 @@ std::error_code mapped_file_region::init(sys::fs::file_t OrigFileHandle,
 
 mapped_file_region::mapped_file_region(sys::fs::file_t fd, mapmode mode,
                                        size_t length, uint64_t offset,
-                                       std::error_code &ec)
+                                       std::error_code &ec, const char* name)
     : Size(length) {
   sandbox::violationIfEnabled();
 
-  ec = init(fd, offset, mode);
+  ec = init(fd, offset, mode, name);
   if (ec)
     copyFrom(mapped_file_region());
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/190692