Improve unique_ptr-y ownership in ASTUnit::ComputePreamble

Rather than having a pair of pairs and a reference out parameter, build
a structure with everything together and named. A raw pointer and a
unique_ptr, rather than a raw pointer and a boolean, are used to
communicate ownership transfer.

It's possible one day we'll end up with a conditional pointer (probably
represented by a raw pointer and a boolean) abstraction to use in places
like this. Conditional ownership seems to be coming up more often than
I'd hoped...

llvm-svn: 216712

2 files changed, 31 insertions, 50 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 31266dca928..38d9aeaaf50 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -1179,17 +1179,16 @@ static std::string GetPreamblePCHPath() {
 /// \brief Compute the preamble for the main file, providing the source buffer
 /// that corresponds to the main file along with a pair (bytes, start-of-line)
 /// that describes the preamble.
-std::pair<llvm::MemoryBuffer *, std::pair<unsigned, bool> > 
-ASTUnit::ComputePreamble(CompilerInvocation &Invocation, 
-                         unsigned MaxLines, bool &CreatedBuffer) {
+ASTUnit::ComputedPreamble
+ASTUnit::ComputePreamble(CompilerInvocation &Invocation, unsigned MaxLines) {
   FrontendOptions &FrontendOpts = Invocation.getFrontendOpts();
   PreprocessorOptions &PreprocessorOpts = Invocation.getPreprocessorOpts();
-  CreatedBuffer = false;
   
   // Try to determine if the main file has been remapped, either from the 
   // command line (to another file) or directly through the compiler invocation
   // (to a memory buffer).
   llvm::MemoryBuffer *Buffer = nullptr;
+  std::unique_ptr<llvm::MemoryBuffer> BufferOwner;
   std::string MainFilePath(FrontendOpts.Inputs[0].getFile());
   llvm::sys::fs::UniqueID MainFileID;
   if (!llvm::sys::fs::getUniqueID(MainFilePath, MainFileID)) {
@@ -1200,15 +1199,9 @@ ASTUnit::ComputePreamble(CompilerInvocation &Invocation,
       if (!llvm::sys::fs::getUniqueID(MPath, MID)) {
         if (MainFileID == MID) {
           // We found a remapping. Try to load the resulting, remapped source.
-          if (CreatedBuffer) {
-            delete Buffer;
-            CreatedBuffer = false;
-          }
-
-          Buffer = getBufferForFile(RF.second).release();
-          if (!Buffer)
-            return std::make_pair(nullptr, std::make_pair(0, true));
-          CreatedBuffer = true;
+          BufferOwner = getBufferForFile(RF.second);
+          if (!BufferOwner)
+            return ComputedPreamble(nullptr, nullptr, 0, true);
         }
       }
     }
@@ -1221,11 +1214,7 @@ ASTUnit::ComputePreamble(CompilerInvocation &Invocation,
       if (!llvm::sys::fs::getUniqueID(MPath, MID)) {
         if (MainFileID == MID) {
           // We found a remapping.
-          if (CreatedBuffer) {
-            delete Buffer;
-            CreatedBuffer = false;
-          }
-
+          BufferOwner.reset();
           Buffer = const_cast<llvm::MemoryBuffer *>(RB.second);
         }
       }
@@ -1233,17 +1222,18 @@ ASTUnit::ComputePreamble(CompilerInvocation &Invocation,
   }
   
   // If the main source file was not remapped, load it now.
-  if (!Buffer) {
-    Buffer = getBufferForFile(FrontendOpts.Inputs[0].getFile()).release();
-    if (!Buffer)
-      return std::make_pair(nullptr, std::make_pair(0, true));
-
-    CreatedBuffer = true;
+  if (!Buffer && !BufferOwner) {
+    BufferOwner = getBufferForFile(FrontendOpts.Inputs[0].getFile());
+    if (!BufferOwner)
+      return ComputedPreamble(nullptr, nullptr, 0, true);
   }
 
-  return std::make_pair(
-      Buffer, Lexer::ComputePreamble(Buffer->getBuffer(),
-                                     *Invocation.getLangOpts(), MaxLines));
+  if (!Buffer)
+    Buffer = BufferOwner.get();
+  auto Pre = Lexer::ComputePreamble(Buffer->getBuffer(),
+                                    *Invocation.getLangOpts(), MaxLines);
+  return ComputedPreamble(Buffer, std::move(BufferOwner), Pre.first,
+                          Pre.second);
 }
 
 ASTUnit::PreambleFileHash
@@ -1354,16 +1344,9 @@ ASTUnit::getMainBufferWithPrecompiledPreamble(
   PreprocessorOptions &PreprocessorOpts
     = PreambleInvocation->getPreprocessorOpts();
 
-  bool CreatedPreambleBuffer = false;
-  std::pair<llvm::MemoryBuffer *, std::pair<unsigned, bool> > NewPreamble 
-    = ComputePreamble(*PreambleInvocation, MaxLines, CreatedPreambleBuffer);
-
-  // If ComputePreamble() Take ownership of the preamble buffer.
-  std::unique_ptr<llvm::MemoryBuffer> OwnedPreambleBuffer;
-  if (CreatedPreambleBuffer)
-    OwnedPreambleBuffer.reset(NewPreamble.first);
+  ComputedPreamble NewPreamble = ComputePreamble(*PreambleInvocation, MaxLines);
 
-  if (!NewPreamble.second.first) {
+  if (!NewPreamble.Size) {
     // We couldn't find a preamble in the main source. Clear out the current
     // preamble, if we have one. It's obviously no good any more.
     Preamble.clear();
@@ -1379,10 +1362,10 @@ ASTUnit::getMainBufferWithPrecompiledPreamble(
     // preamble now that we did before, and that there's enough space in
     // the main-file buffer within the precompiled preamble to fit the
     // new main file.
-    if (Preamble.size() == NewPreamble.second.first &&
-        PreambleEndsAtStartOfLine == NewPreamble.second.second &&
-        memcmp(Preamble.getBufferStart(), NewPreamble.first->getBufferStart(),
-               NewPreamble.second.first) == 0) {
+    if (Preamble.size() == NewPreamble.Size &&
+        PreambleEndsAtStartOfLine == NewPreamble.PreambleEndsAtStartOfLine &&
+        memcmp(Preamble.getBufferStart(), NewPreamble.Buffer->getBufferStart(),
+               NewPreamble.Size) == 0) {
       // The preamble has not changed. We may be able to re-use the precompiled
       // preamble.
 
@@ -1452,7 +1435,7 @@ ASTUnit::getMainBufferWithPrecompiledPreamble(
         getDiagnostics().setNumWarnings(NumWarningsInPreamble);
 
         return llvm::MemoryBuffer::getMemBufferCopy(
-            NewPreamble.first->getBuffer(), FrontendOpts.Inputs[0].getFile());
+            NewPreamble.Buffer->getBuffer(), FrontendOpts.Inputs[0].getFile());
       }
     }
 
@@ -1497,13 +1480,12 @@ ASTUnit::getMainBufferWithPrecompiledPreamble(
   // subsequent reparses.
   StringRef MainFilename = FrontendOpts.Inputs[0].getFile();
   Preamble.assign(FileMgr->getFile(MainFilename),
-                  NewPreamble.first->getBufferStart(), 
-                  NewPreamble.first->getBufferStart() 
-                                                  + NewPreamble.second.first);
-  PreambleEndsAtStartOfLine = NewPreamble.second.second;
+                  NewPreamble.Buffer->getBufferStart(),
+                  NewPreamble.Buffer->getBufferStart() + NewPreamble.Size);
+  PreambleEndsAtStartOfLine = NewPreamble.PreambleEndsAtStartOfLine;
 
   PreambleBuffer = llvm::MemoryBuffer::getMemBufferCopy(
-      NewPreamble.first->getBuffer().slice(0, Preamble.size()), MainFilename);
+      NewPreamble.Buffer->getBuffer().slice(0, Preamble.size()), MainFilename);
 
   // Remap the main source file to the preamble buffer.
   StringRef MainFilePath = FrontendOpts.Inputs[0].getFile();
@@ -1647,7 +1629,7 @@ ASTUnit::getMainBufferWithPrecompiledPreamble(
     PreambleTopLevelHashValue = CurrentTopLevelHashValue;
   }
 
-  return llvm::MemoryBuffer::getMemBufferCopy(NewPreamble.first->getBuffer(),
+  return llvm::MemoryBuffer::getMemBufferCopy(NewPreamble.Buffer->getBuffer(),
                                               MainFilename);
 }
 
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index 0e251276259..99cd4a2e6d6 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -683,9 +683,8 @@ void PrintPreambleAction::ExecuteAction() {
   }
 
   CompilerInstance &CI = getCompilerInstance();
-  std::unique_ptr<llvm::MemoryBuffer> Buffer
-      = CI.getFileManager().getBufferForFile(getCurrentFile());
-  if (Buffer) {
+  if (std::unique_ptr<llvm::MemoryBuffer> Buffer =
+          CI.getFileManager().getBufferForFile(getCurrentFile())) {
     unsigned Preamble =
         Lexer::ComputePreamble(Buffer->getBuffer(), CI.getLangOpts()).first;
     llvm::outs().write(Buffer->getBufferStart(), Preamble);