The Problem with Base Profiles

Oct 13, 2025 by wbrum.org 132 views

Understanding the Issue

When working with C++ settings, it's common to define a base profile that includes essential settings, which are then inherited by other profiles that use different compilers. However, this approach can lead to errors, such as ERROR: 'settings.compiler' value not defined. In this article, we'll explore this issue and discuss potential improvements to the profile inheritance mechanism.

The Problem with Base Profiles

Let's take a closer look at the example provided:

Base Profile

[settings]
compiler.cppstd=17

Real Profile

include(base)

[settings]
arch=armv8
compiler=clang
compiler.libcxx=c++_shared
compiler.version=18
os=Android

In this example, the base profile defines the compiler.cppstd setting, which is set to 17. However, when the real profile includes the base profile, it attempts to override the compiler setting, which is not defined in the base profile. This results in the ERROR: 'settings.compiler' value not defined error.

Why This Behavior Exists

The reason for this behavior is that the profile inheritance mechanism is designed to ensure that settings are not overridden without a clear intention to do so. By not defining the compiler setting in the base profile, we're indicating that it's not a required setting for all profiles. However, this can lead to confusion and errors, especially when working with complex settings.

Potential Improvements

To improve the profile inheritance mechanism, we could consider the following changes:

1. Allow Optional Settings

One possible solution is to allow optional settings in the base profile. This would enable us to define settings that are not required for all profiles, but can be overridden if needed. For example:

Base Profile

[settings]
compiler.cppstd=17 (optional)

Real Profile

include(base)

[settings]
arch=armv8
compiler=clang
compiler.libcxx=c++_shared
compiler.version=18
os=Android

In this example, the compiler.cppstd setting is marked as optional, allowing the real profile to override it if needed.

2. Introduce a New Setting Type

Another potential solution is to introduce a new setting type, such as inherit, which would indicate that a setting should be inherited from the base profile. For example:

Base Profile

[settings]
compiler.cppstd=17
compiler.inherit=true

Real Profile

include(base)

[settings]
arch=armv8
compiler=clang
compiler.libcxx=c++_shared
compiler.version=18
os=Android

In this example, the compiler setting is marked as inherited, ensuring that it's not overridden in the real profile.

Conclusion

In conclusion, the issue with base profiles in C++ settings is a common problem that can lead to errors and confusion. By introducing optional settings or a new setting type, we can improve the profile inheritance mechanism and make it more flexible and user-friendly. However, further discussion and testing are required to determine the best approach.

Future Work

To further improve the profile inheritance mechanism, we could consider the following future work:

1. Implement Optional Settings

Implementing optional settings would allow us to define settings that are not required for all profiles, but can be overridden if needed.

2. Introduce a New Setting Type

Introducing a new setting type, such as inherit, would enable us to mark settings as inherited from the base profile.

3. Improve Error Messages

Improving error messages would help users understand the cause of errors and provide more accurate information about the settings that need to be defined.

Q: What is profile inheritance in C++ settings?

A: Profile inheritance is a mechanism that allows you to define a base profile with essential settings, which are then inherited by other profiles that use different compilers.

Q: Why do I get the `ERROR: 'settings.compiler' value not defined` error?

A: This error occurs when you attempt to override a setting that is not defined in the base profile. To resolve this issue, you can either define the setting in the base profile or use an optional setting.

Q: What is an optional setting?

A: An optional setting is a setting that is not required for all profiles, but can be overridden if needed. Optional settings are marked with the (optional) keyword.

Q: How do I implement optional settings?

A: To implement optional settings, you can add the (optional) keyword to the setting in the base profile. For example:

Base Profile

[settings]
compiler.cppstd=17 (optional)

Q: What is the `inherit` setting type?

A: The inherit setting type is a new setting type that indicates a setting should be inherited from the base profile. This setting type is not yet implemented.

Q: How do I implement the `inherit` setting type?

A: To implement the inherit setting type, you can add the inherit keyword to the setting in the base profile. For example:

Base Profile

[settings]
compiler.cppstd=17
compiler.inherit=true

Q: Why is the `inherit` setting type not yet implemented?

A: The inherit setting type is not yet implemented because it requires further discussion and testing to determine the best approach.

Q: How can I improve the profile inheritance mechanism?

A: You can improve the profile inheritance mechanism by:

Implementing optional settings
Introducing a new setting type, such as inherit
Improving error messages

Q: What is the future work plan for profile inheritance?

A: The future work plan for profile inheritance includes:

Implementing optional settings
Introducing a new setting type, such as inherit
Improving error messages

Q: How can I contribute to the profile inheritance mechanism?

A: You can contribute to the profile inheritance mechanism by:

Reporting issues and providing feedback
Participating in discussions and testing
Submitting patches and pull requests

By answering these frequently asked questions, we hope to provide a better understanding of the profile inheritance mechanism and its limitations. If you have any further questions or concerns, please don't hesitate to reach out.