How to Use CMake with an HC12 Compiler That Doesn't Support the -o Flag

Learn how to configure CMake for an `HC12` compiler without the `-o` flag. Troubleshoot and adjust settings for a seamless build experience!
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This video is based on the question https://stackoverflow.com/q/70615106/ asked by the user 'Bruce Haines' ( https://stackoverflow.com/u/11789532/ ) and on the answer https://stackoverflow.com/a/70630964/ provided by the user 'kesselhaus' ( https://stackoverflow.com/u/8321975/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Use CMake with an HC12 Compiler That Doesn't Support the -o Flag

When working with embedded systems, especially with older hardware and compilers like the HC12, developers often face challenges that modern build systems don't directly address. One common issue arises when transitioning from GNU Make to CMake, particularly when the compiler does not support the standard -o option for specifying output filenames. In this guide, we’ll explore how to solve this issue effectively.

The Problem

While developing firmware for the HC12 platform, a developer encountered a significant hurdle: their compiler does not recognize the -o flag typically used in C and C++ to define the output filename. Here's a breakdown of the key points related to the problem:

Compiler Limitation: The HC12 compiler requires a different syntax for specifying the output filename using -objn="name_of_file" instead of the conventional -o.

CMake's Default Behavior: CMake automatically appends the -o flag to the compile commands, leading to compile errors when using the HC12 compiler.

Need for Workaround: As switching to a GCC port is not an option for the developer, a workaround within CMake is essential.

Solution Overview

To resolve this issue, you can create a custom toolchain file for your HC12 compiler by modifying how CMake generates build commands. Here’s a step-by-step guide to achieving that.

Step 1: Create a Custom Toolchain File

You can start by referencing existing toolchain files, like Modules/Compiler/ti.cmake, but customizing it for your specific needs. Here’s how you can set it up:

Define Compiler Flags: Set up the required flags for your compiler as follows:

[[See Video to Reveal this Text or Code Snippet]]

Modify Compilation Commands: Adjust the command used to compile C/C++ objects in CMake’s makefiles. Here’s a macro example for the HC12 compiler:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Integrate the Toolchain into Your Project

Once you've created your custom toolchain file, you need to specify it when configuring your project with CMake. You do this by using the -DCMAKE_TOOLCHAIN_FILE option:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Test the Setup

After configuring CMake with your custom toolchain, compile your project to ensure that it adheres to the HC12 compilation requirements. You should now see the expected output filenames using the -objn flag and no longer encounter errors related to the -o option.

Conclusion

Switching between build systems can be daunting, especially with unique constraints of embedded development. However, by understanding the required modifications in CMake and customizing the toolchain accordingly, you can continue using familiar tools like CMake without sacrificing functionality. This approach not only addresses the lack of support for the -o flag but also lets you leverage CMake’s powerful features to manage your embedded projects seamlessly.

Have you faced similar issues in your embedded development? Share your experiences in the comments below!

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