log_msg constructor doesn't initialize all fields

[curiouserrandy]

The constructors for spdlog::details::log_msg do not initialize all fields of the struct. This can result in failures in consumer code that automatically scans for uninitialized memory accesses. It would be useful for that class to have an explicit default for all fields.

[gabime]

Do you have a concrete example of such scan failure ? Valgrind never complained..

[gabime]

Fixed. Remved the default ctor of log_msg

[curiouserrandy]

The test it was found in was MainCommonTest.ConstructDestructLogger in https://github.com/envoyproxy/envoy/blob/master/test/exe/main_common_test.cc, but it occurred in Google internal testing with Memory Sanitizer, and thus I can't say for sure that valgrind would have caught it (though it seems likely).

I'm about to add a change to that test (changing the constructor from the default one over to the one with arguments, making the variable static for zero-initializing before construction) just to get around this problem. That PR is envoyproxy/envoy#4884, so you may need to click back before whatever commit that lands in if it lands before you look.

Thanks much for the quick fix!

[gabime]

I believe that no unintialized fields exists when using this (fixed) ctor, so no need to make it static. Moreover, the envoy code probably doesnt use static log_msg, so it’s better to test the same usage as in envoy.

[curiouserrandy]

Yep. We'll try to switch it back the next time envoy upgrades its dependent spdlog.