How to Fix Linker Script Errors: Step-by-Step Guide

Identify the Error Message

• Linker script errors usually have descriptive messages. Start by reading the error output carefully.
• Look for symbols that could not be resolved, addresses that overlap, or unexpected memory region behaviors.

Review the Linker Script

• Verify that the linker script matches your microcontroller's or processor's memory specification. Ensure that FLASH and RAM sizes are correctly defined.
• Check the syntax of your script. Common issues arise from missing sections or incorrect memory alignment.

Examine the Memory Sections

• Ensure all sections like `.text`, `.data`, `.bss`, and custom sections have correct memory regions assigned.
• Review attribute placements in your code. For instance, placing code in the correct section by using GCC `__attribute__((section(".mysection")))`.

Check Symbol Definitions

• Review the definitions of symbols that the linker cannot resolve. Ensure they are correctly declared in your code and properly referenced in assembly if used.
• Examine any conditional compilation (`#ifdef`s) that might exclude necessary code in certain build configurations.

Adjust Memory Allocation

• If sections are too large, review code for large arrays or buffers and consider reducing or dynamically allocating them.
• Check alignment settings, especially for sections requiring specific boundaries.

Verify External Dependencies

• Check for library versions and compile settings to ensure compatibility. A mismatched ABI can cause linking errors.
• Make sure paths to external libraries and headers are correctly specified in makefiles or build-system scripts.

Use Map Files

• Enable generation of a map file when linking. This provides a detailed view of memory usage and symbol locations.
• Check the map file to understand where each section and symbol is placed. This helps diagnose overlaps or address alignment issues.

Incremental Approach

• Simplify your code to the smallest example that still causes the error. Segregate sections to see which change resolves the issue.
• Gradually re-integrate your code changes to ensure that errors do not re-appear, enhancing your understanding of the root cause.

Seek Community Help

• If stuck, consult with online communities and forums related to your hardware or toolchain. Often, others have faced similar issues.
• Provide a detailed description and any error messages when seeking assistance to streamline the troubleshooting process.

Example: Custom Section Placement

• To place a specific function in a custom section, declare it like this:

  void MyFunction(void) **attribute**((section(".custom\_section")));

• Then define the `.custom_section` in your linker script:

  SECTIONS {
    .custom\_section : {
      KEEP(\*(.custom\_section))
    } > RAM
  }