[TSan] Fix warning when compiling with -Wmissing-designated-field-initializers

[DanBlackwell]

Currently we receive a warning when initializing a ThreadEventCallbacks when compiling with this flag:

llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp:252:3: warning: missing field 'start' initializer [-Wmissing-designated-field-initializers]
  252 |   };
      |   ^

This patch explicitly initializes the missing fields to null, fixing the warning.

rdar://162074310

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Dan Blackwell (DanBlackwell)

Changes

Currently we receive a warning when initializing a ThreadEventCallbacks when compiling with this flag:

llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp:252:3: warning: missing field 'start' initializer [-Wmissing-designated-field-initializers]
  252 |   };
      |   ^

This patch explicitly initializes the missing fields to null, fixing the warning.

rdar://162074310

---

Full diff: https://github.com/llvm/llvm-project/pull/163401.diff

1 Files Affected:

• (modified) compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp (+2)

diff --git a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
index 62ab0554df08e..7fa5e017d3985 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
@@ -259,7 +259,9 @@ void InitializePlatform() {
 
   ThreadEventCallbacks callbacks = {
       .create = ThreadCreateCallback,
+      .start = nullptr,
       .terminate = ThreadTerminateCallback,
+      .destroy = nullptr,
   };
   InstallPthreadIntrospectionHook(callbacks);
 #endif

[yln]

Interesting. I thought unmentioned members are guaranteed to be default-initialized.

The semantics of the warning seem to be under discussion:
#68933
#56628

Did this warning pop up with a new version of Clang or was it always there?

[DanBlackwell]

This was picked up by someone building https://github.com/swiftlang/swift (which depends on llvm-project). It seems that they are setting -Wmissing-designated-field-initializers somehow. I rebuilt compiler-rt with the flag and this was the only warning I got, so I figured it's easy enough to clean up. I don't think that the standard llvm CMake build will hit this error, I had to add the flag to my CMAKE_CXX_FLAGS to trigger this.

I agree that this warning feels pedantic.