support for debug/release builds in Arduino IDE 2.x

[m-mcgowan]

This is a feature request (which I'm happy to implement) and a request for comments.

Background

Arduino IDE 2.x supports debugging, and with that, has a new menu option Sketch > Optimize for Debugging.

This looks like a convenient way to enable debugging builds with symbols from within the IDE and provides a standard means of compiling a debug build with the CLI.

Under the hood

The Optimize for Debugging option sets the compiler.optimization_flags placeholder from either compiler.optimization_flags.debug or compiler.optimization_flags.release according to the setting chosen. (The debugging section in the platform spec explains this more fully.)

boards.txt currently defines menus for the optimization level, and whether symbols and/or core logs are compiled in. The overlap in functionality between these existing selection and the new "Optimize for Debugging" selection may need to be resolved.

Possible Implementation

As a starting point platform.txt would have two new placeholders defined, corresponding to the flags used for debug and release builds:

compiler.optimization_flags.debug=-g
compiler.optimization_flags.release=-DNDEBUG

The build environment then sets compiler.optimization_flags from either of these two, which we could propagate via compiler.extra_flags:

compiler.extra_flags=-mcpu={build.mcu} {compiler.optimization_flags} {...etc...}

With this in place, the Debug setting always includes debug symbols, and the Release setting does not include system logs, irrespective of the setting of the Debug symbols and core logs menu item. This seems to be the least element of surprise and does "the right thing" for debug and release builds, although it may not be obvious to users that the Optimize for Debugging menu selection takes precedence over the Debug symbols and core logs menu selection when it comes to enabling/disabling core logs.

Alternatively, the compiler.optimization_flags.release value could be left empty, which would mean that a release build uses the selection from Debug symbols and core logs exclusively, while the debug build always contains symbols, plus core logs when selected.

The latter approach seems somewhat "dangerous" in that it puts the onus on the user to be certain to deselect core logs in a release build.

If I were asked to make the choice, I would lean more towards the first approach with release builds explicitly excluding core logs, simply because it feels more in line with what a developer would expect for a release build, but that's just my casual suggestion. The community here may see other alternatives, or have good reasons to prefer the second approach, which I look forward to learning about and discussing.

Once we've established the most desirable way forward, I would be happy to make the changes needed and submit a PR.

[fpistm]

Hi @m-mcgowan
Thanks for this issue.
I know this option in the IDE 2.x but did not deploy it as Arduino debug feature is not stable (let's say beta).
As you pointed we already have menu which could cause some conflict and/or issue with Arduino 1.x compatibility (not check this yet).
Moreover the boards.txt is very limited and so hard to properly set correct combination.
I guess removing Debug symbols and core logs could be easy as you proposed but what about Arduino IDE 1.x, I don't think the menu Optimize for Debugging exists.
And don"t know how to manage -0g maybe gcc uses the last one defined?

[m-mcgowan]

If we implement via the {compiler.optimization_flags} placeholder then this will be silently ignored by Arduino IDE 1.x and older versions of the CLI. (I believe undefined placeholders evaluate to the empty string, but I can verify that when testing.).

A third option I didn't mention that occurs to me now is to make no change - leave things as they are. This could be acceptable if we document that the "Optimize for Debugging" option does nothing. This wasn't immediately clear to me when I started experimenting with the debug feature.

I can appreciate adding the new Optimize for Debugging option with the existing menus is tricky with the limitations of boards.txt :-) I'd be happy to do some experimentation to help find out what is workable/possible, such as investigating if we can have multiple optimization flags ordered so that the "Optimize for Debugging" setting takes precedence.

Although debugging is still a "beta" feature, I've been using the debugger quite extensively lately and it seems pretty stable!

[fpistm]

Hi @m-mcgowan
I've made a PR #2184 to add this support. Tested with Arduino IDE 1.x and 2.x.