Identifying the Cause
- The error "section '.text' will not fit in region 'FLASH'" indicates that the size of your program's text section (which contains executable code) exceeds the available FLASH memory on your microcontroller.
- Ensure you're compiling your program with the correct microcontroller specifications. Incorrect specs can lead to memory allocation errors.
- Check your linker script for correct memory region allocations. An outdated or incorrect linker script can lead to allocation issues.
Optimize Code Size
- Use compiler optimization flags specifically aimed at reducing code size. For GCC, this means using
-Os to optimize for size.
- Investigate and refactor large sections of code to identify unnecessary code. Aggressively simplify wherever possible without losing critical functionality.
- Remove dead code that isn't contributing to the final application. These can be legacy code segments or parts of the project that are no longer called.
Optimize Libraries and Frameworks
- Review third-party libraries included in your firmware. Many include optional modules or features that consume valuable FLASH memory.
- Use alternate or slimmer libraries when possible. For example, replacing a general-purpose library with a more specific one that fits your exact needs.
- Evaluate your use of C++ templates, as they can increase code size. Consider using explicit template instantiation sparingly.
Adjusting the Linker Script
- Ensure that your linker script defines sections and regions accurately according to your microcontroller's FLASH size. Adjust if necessary.
- Verify the boundaries of the FLASH region in the linker script match the specifications of the target microcontroller.
- If appropriate for your application, you might consider moving some frequently executed library functions to RAM if available. This is typically done using linker attributes.
Configure Conditional Compilation
- Use preprocessor directives to conditionally compile only the necessary code segments for specific application needs.
- Analyze build configurations and reduce the number of debugging information and logs compiled into the release version of your firmware.
- For instance, use guards like
#ifdef DEBUG to exclude sections that are only needed during development.
Review MCU Configuration
- Double-check that the microcontroller's configuration register setup aligns with what the development environment and linker script expect.
- Determine if memory protection settings (such as MPU) could be mistakenly configured, impacting memory allocations.
Use of LTO (Link Time Optimization)
- Enable Link Time Optimization (LTO) if your toolchain supports it. This can lead to significant reductions in code size by optimizing across translation units.
- Use flags like
-flto during both the compilation and linking stages to activate LTO.
Split Functionality Across FLASH Regions
- If your microcontroller supports multiple FLASH banks or regions, strategically allocate certain code sections to different banks.
- This requires careful planning and customizing the linker script to specify which functions or objects belong in each section.
These strategies should be combined and iteratively applied to successfully resolve instances where the '.text' section does not fit within the 'FLASH' region, allowing the firmware to be correctly compiled and loaded onto the target microcontroller.
