[asan] Turn -fsanitize-address-use-after-scope on by default

[kubamracek]

Summary

AddressSanitizer has an optional compile-time flag, -fsanitize-address-use-after-scope, which enables detection of use-after-scope bugs. We'd like to have this feature on by default, because it is already very well tested, it's used in several projects already (LLVM automatically enables it when using -DLLVM_USE_SANITIZER=Address), it's low overhead and there are no known issues or incompatibilities.

This patch enables use-after-scope by default via the Clang driver, where we set true as the default value for AsanUseAfterScope. This also causes the lifetime markers to be generated whenever fsanitize=address is used. This has some nice consequences, e.g. we now have line numbers for all local variables. Several testcases needed to be updated to address this change. The ParseFrameDescription function needed to be updated to properly parse "varname:line".

[vitalybuka]

LGTM, but could you split this patch into two?

1. ParseFrameDescription change
2. AsanUseAfterScope = true

[kubamracek]

I extracted the StackVarDescr change into https://reviews.llvm.org/D31484. This patch now simply just enables -fsanitize-address-use-after-scope by default.

[vitalybuka]

Thank you! LGTM

cfe/trunk/include/clang/Driver/SanitizerArgs.h

class SanitizerArgs {
   std::vector<std::string> BlacklistFiles;
   std::vector<std::string> ExtraDeps;
   int CoverageFeatures = 0;
   int MsanTrackOrigins = 0;
   bool MsanUseAfterDtor = false;
   bool CfiCrossDso = false;
   int AsanFieldPadding = 0;
   bool AsanSharedRuntime = false;
-  bool AsanUseAfterScope = false;
+  bool AsanUseAfterScope = true;
   bool LinkCXXRuntimes = false;
   bool NeedPIE = false;
   bool Stats = false;
   bool TsanMemoryAccess = true;
   bool TsanFuncEntryExit = true;
   bool TsanAtomics = true;
 
  public:

cfe/trunk/test/Driver/fsanitize.c

 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address -fno-sanitize-address-use-after-scope -fsanitize-address-use-after-scope %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-USE-AFTER-SCOPE-BOTH
 // CHECK-USE-AFTER-SCOPE-BOTH: -cc1{{.*}}-fsanitize-address-use-after-scope
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-after-scope -fno-sanitize-address-use-after-scope %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-USE-AFTER-SCOPE-BOTH-OFF
 // CHECK-USE-AFTER-SCOPE-BOTH-OFF-NOT: -cc1{{.*}}address-use-after-scope
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-WITHOUT-USE-AFTER-SCOPE
-// CHECK-ASAN-WITHOUT-USE-AFTER-SCOPE-NOT: -cc1{{.*}}address-use-after-scope
+// CHECK-ASAN-WITHOUT-USE-AFTER-SCOPE: -cc1{{.*}}address-use-after-scope
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ONLY-TRACK-ORIGINS
 // CHECK-ONLY-TRACK-ORIGINS: warning: argument unused during compilation: '-fsanitize-memory-track-origins'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fno-sanitize=memory -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-DISABLED-MSAN
 // CHECK-TRACK-ORIGINS-DISABLED-MSAN-NOT: warning: argument unused
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-EXTRA-TRACK-ORIGINS