"target_overrides" unhandy for "macros" with values

[betzw]

Description

• Type: Enhancement
• Priority: Minor

---

Enhancement

Reason to enhance or problem with existing solution
When trying to override the value of a macro defined in targets.json for an application in file mbed_app.json I didn't find a better way then first removing the first macro including its value and then add the macro with its new value (all my other trials either didn't work or produced ugly compiler warnings), e.g. like this:

{
    "target_overrides": {
        "*": {
           "target.macros_remove": ["TRANSACTION_QUEUE_SIZE_SPI=2"],
           "target.macros_add": ["TRANSACTION_QUEUE_SIZE_SPI=0"]
       }
    }
}

Suggested enhancement
The unfortunate things here are that we need two lines to express what we want to do and above all that we need to know also the original value of the macro. Unfortunately, this value could even be different from platform to platform, which would require to specify the overrides for each platform we are targeting in our application!
Therefore, I would propose some additional syntax like this:

{
    "target_overrides": {
        "*": {
           "target.macros_value": ["TRANSACTION_QUEUE_SIZE_SPI=0"]       
        }
    }
}

Pros

• No need to know & specify the original value, which might be different from platform to platform
• Simpler syntax

[0xc0170]

@bogdanm @theotherjimmy

[bogdanm]

The purpose of macros_add was to allow for cumulative values: you add this macro to the list of macros you inherit from your base target(s) (same goes for remove). When you use target.macro_values, is that still cumulative, or does it just set the macro values (without inheriting the other macros from the base target(s))? It feels a bit strange. We could introduce macros_replace to combine macro_add and macros_remove in a single operation, would that help?

[betzw]

The operation would not be cumulative but is intended to replace the value assigned to an inherited macro by another value without having to specify the original value of the inherited macro (because this one could be different for any target).
Note: with value I do not intend the macro's name but just what comes after the equal = sign!

[bogdanm]

I believe macros_replace is a better name,, and we can certainly implement that.

[betzw]

Actually, I do not care about the name.

[betzw]

Any news on this @bogdanm?

[bogdanm]

Cc @theotherjimmy

[theotherjimmy]

This has not been high priority for me. Sorry, but I have not started on it yet.

[betzw]

With the latest modifications to mbed-cli even my original approach (i.e. removing the macro with its original value and adding it again with the new value) does not work anymore. Could you pls. re-consider the proposal I have made here again?
Thanks in advance!

@theotherjimmy @screamerbg

[RobMeades]

I also hit this issue recently when I wanted to change the value of a macro defined in targets.json from mbed_app.json. I agree with @betzw that having to do, in my case:

            "target.macros_remove": ["HSE_VALUE=12000000"],
            "target.macros_add": ["HSE_VALUE=8000000"]

...is a bit cumbersome and a mechanism for simply changing the value would be a good improvement. However, it is worth pointing out that the above did work for me (code as at start of March 2017 I think).

[0xc0170]

Why don't we use config for this, using macros with values does not look right - thus the syntax add/remove as you have to use the very same definition =VALUE ?

[theotherjimmy]

@0xc0170 I agree: we should use config instead.