Fixed double-free in case of module loading error.

[tra]

Summary

GetOutputStream() owns the stream it returns pointer to and the
pointer should never be freed by us. When we fail to load and exit
early, unique_ptr still holds the pointer and frees it which leads to
compiler crash when CompilerInstance attempts to free it again.

Added regression test for failed bitcode linking.

[tra]

Use assignment to init the pointer.

[rnk]

lgtm

cfe/trunk/lib/CodeGen/CodeGenAction.cpp

GetOutputStream(CompilerInstance &CI, StringRef InFile, BackendAction Action) {
   }
 
   llvm_unreachable("Invalid action!");
 }
 
 std::unique_ptr<ASTConsumer>
 CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   BackendAction BA = static_cast<BackendAction>(Act);
-  std::unique_ptr<raw_pwrite_stream> OS(GetOutputStream(CI, InFile, BA));
+  raw_pwrite_stream *OS = GetOutputStream(CI, InFile, BA);
   if (BA != Backend_EmitNothing && !OS)
     return nullptr;
 
   llvm::Module *LinkModuleToUse = LinkModule;
 
   // If we were not given a link module, and the user requested that one be
   // loaded from bitcode, do so now.
   const std::string &LinkBCFile = CI.getCodeGenOpts().LinkBitcodeFile;
CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   if (CI.getCodeGenOpts().CoverageMapping) {
     CoverageInfo = new CoverageSourceInfo;
     CI.getPreprocessor().addPPCallbacks(
                                     std::unique_ptr<PPCallbacks>(CoverageInfo));
   }
   std::unique_ptr<BackendConsumer> Result(new BackendConsumer(
       BA, CI.getDiagnostics(), CI.getCodeGenOpts(), CI.getTargetOpts(),
       CI.getLangOpts(), CI.getFrontendOpts().ShowTimers, InFile,
-      LinkModuleToUse, OS.release(), *VMContext, CoverageInfo));
+      LinkModuleToUse, OS, *VMContext, CoverageInfo));
   BEConsumer = Result.get();
   return std::move(Result);
 }
 
 static void BitcodeInlineAsmDiagHandler(const llvm::SMDiagnostic &SM,
                                          void *Context,
                                          unsigned LocCookie) {
   SM.print(nullptr, llvm::errs());

cfe/trunk/test/CodeGen/link-bitcode-file.c

 // RUN: %clang_cc1 -triple i386-pc-linux-gnu -DBITCODE -emit-llvm-bc -o %t.bc %s
 // RUN: %clang_cc1 -triple i386-pc-linux-gnu -mlink-bitcode-file %t.bc -O3 -emit-llvm -o - %s | FileCheck -check-prefix=CHECK-NO-BC %s
 // RUN: not %clang_cc1 -triple i386-pc-linux-gnu -DBITCODE -mlink-bitcode-file %t.bc -O3 -emit-llvm -o - %s 2>&1 | FileCheck -check-prefix=CHECK-BC %s
+// Make sure we deal with failure to load the file.
+// RUN: not %clang_cc1 -triple i386-pc-linux-gnu -mlink-bitcode-file no-such-file.bc \
+// RUN:    -emit-llvm -o - %s 2>&1 | FileCheck -check-prefix=CHECK-NO-FILE %s
 
 int f(void);
 
 #ifdef BITCODE
 
 // CHECK-BC: fatal error: cannot link module {{.*}}'f': symbol multiply defined
 int f(void) {
   return 42;
 }
 
 #else
 
 // CHECK-NO-BC-LABEL: define i32 @g
 // CHECK-NO-BC: ret i32 42
 int g(void) {
   return f();
 }
 
 // CHECK-NO-BC-LABEL: define i32 @f
 
 #endif
+
+// CHECK-NO-FILE: fatal error: cannot open file 'no-such-file.bc'