Control release mode debug logging output by ENABLE_DEBUG_LOGGING option

[wangyoucao577]

Issue

What issue is this PR targeting? If there is no issue that addresses the problem, please open a corresponding issue and link it here.
#3427

Please read our documentation on release and version management.
If your PR is still work in progress please attach the relevant label.

Tasklist

• CHANGELOG.md entry (How to write a changelog entry)
• update relevant Wiki pages
• add tests (see testing documentation
• review
• adjust for comments
• cherry pick to release branch

Requirements / Relations

Link any requirements here. Other pull requests this PR is based on?

[wangyoucao577]

As I write in #3427 (comment), the performance of debug log is acceptable.

[akashihi]

Can it be a compile time option? So one will be able to choose, whether debug output should not be compiled at all in release mode, or compiled in but not visible by default?

[wangyoucao577]

Can it be a compile time option? So one will be able to choose, whether debug output should not be compiled at all in release mode, or compiled in but not visible by default?

Technically it's ok to be a compile time option, actually the NDEBUG is already the one. However, is it really valuable to control it by compiling? Intutively people will expect to have the debug log simply by -l DEBUG at runtime, that what I was thought before really deep dive the code. It really made bothered me for a long time. So that I stronglly suggest to remove the compile time control.

[danpat]

I think whether performance is acceptable or not depents where the debug log output is being generated. If someone places a debug message in one of the important loops during data processing, even if logging is suppressed, it could increase processing time.

My preference would be to leave the current behaviour by default - compile-time-disable debug logging, but may be add a CMake rule that enables debug logging for release builds if it's desired.

[wangyoucao577]

I think whether performance is acceptable or not depents where the debug log output is being generated. If someone places a debug message in one of the important loops during data processing, even if logging is suppressed, it could increase processing time.

My preference would be to leave the current behaviour by default - compile-time-disable debug logging, but may be add a CMake rule that enables debug logging for release builds if it's desired.

@danpat I have added cmake option ENABLE_DEBUG_LOGGING as you suggested. Its behavior is very similar with ENABLE_ASSERTIONS that defaully ON in debug mode and OFF in release mode. With -DENABLE_DEBUG_LOGGING=ON it can be enabled in release mode also. Please help to review it. Thanks!

[akashihi]

Looks good for me!

@danpat @gardster Any objections to merge this?