Cross Compilation with a Custom Linker Fails: A Comprehensive Guide to Troubleshooting

Are you tired of dealing with the frustrations of cross-compilation with a custom linker? You’re not alone! In this article, we’ll delve into the common issues that arise when attempting to cross-compile with a custom linker and provide you with step-by-step solutions to get you back on track.

What is Cross Compilation and Why Do We Need Custom Linkers?

Cross-compilation is the process of compiling code on one platform (the build platform) to run on another platform (the target platform). For instance, you might want to compile code on your Windows machine to run on a Linux-based embedded system. This process requires a cross-compiler, which is a special type of compiler that can generate machine code for the target platform.

In some cases, the default linker that comes with the cross-compiler might not be suitable for your project’s specific needs. That’s where custom linkers come in – they offer more flexibility and customization options to ensure that your code is linked correctly.

Common Issues with Cross Compilation and Custom Linkers

So, what can go wrong when attempting to cross-compile with a custom linker? Here are some common issues you might encounter:

• ld: cannot find -lcustom_lib: The linker can’t locate the custom library you’ve created.
• undefined reference to 'symbol': The linker can’t find a specific symbol (function or variable) in your custom library.
• relocation truncated to fit: The linker is having trouble resolving relocation addresses.
• symbol multiple definition: The linker has encountered multiple definitions of the same symbol.

Troubleshooting Steps for Cross Compilation with a Custom Linker

Don’t panic! We’ll walk you through a series of troubleshooting steps to help you identify and fix the issues with your cross-compilation process.

Step 1: Verify Your Custom Linker Script

The first step is to ensure that your custom linker script is correct and properly formatted. A linker script is a text file that tells the linker how to organize the output file.

MEMORY
{
  flash   : ORIGIN = 0x00000000, LENGTH = 0x40000
  sram   : ORIGIN = 0x20000000, LENGTH = 0x80000
}

SECTIONS
{
  .text :
  {
    *(.text)
  } > flash

  .data :
  {
    *(.data)
  } > sram

  .bss :
  {
    *(.bss)
  } > sram
}

In this example, we’re defining the memory layout for our target platform, specifying the origin and length of the flash and SRAM regions.

Step 2: Check Your Custom Library’s Compilation

Make sure that your custom library is compiled correctly and that the resulting object files are in the correct location.

Command	Purpose
gcc -c custom_lib.c -o custom_lib.o	Compile the custom library source file into an object file.
ar rcs libcustom_lib.a custom_lib.o	Create a static library archive from the object file.

Step 3: Verify the Linker Command Line

The linker command line should include the necessary flags and options to instruct the linker to use your custom linker script and library.

gcc -Wl,--script=my_linker_script.ld -L. -lcustom_lib main.c -o output

In this example, we’re telling the linker to use the my_linker_script.ld script, search for libraries in the current directory (-L.), and link against the libcustom_lib.a library.

Step 4: Check for Symbol Visibility

If the linker is complaining about undefined symbols, it might be due to incorrect symbol visibility. Make sure that the symbols you’re using are exported correctly in your custom library.

extern "C" {
  void my_symbol(void);
}

In this example, we’re using the extern "C" keyword to ensure that the my_symbol function is exported with C linkage.

Step 5: Inspect the Linker Output

Take a closer look at the linker output to identify any errors or warnings that might be relevant to your issue.

ld: warning: section '.text' type changed to PROGBITS
ld: warning: section '.data' type changed to PROGBITS
ld: error: relocation truncated to fit: R_ARM_MOVW_ABS_NC against symbol `my_symbol' defined in .text section in libcustom_lib.a(custom_lib.o)

In this example, the linker is warning us about changes to the section types and ultimately errors out due to a relocation issue with the my_symbol function.

Step 6: Consult the Linker Documentation

If all else fails, consult the linker documentation for your specific cross-compiler and target platform. You might find additional flags or options that can help resolve the issue.

For example, the GNU ld documentation provides detailed information on the various options and flags available for customization.

Conclusion

Cross-compilation with a custom linker can be a daunting task, but by following these troubleshooting steps, you’ll be well-equipped to overcome the common issues that arise. Remember to:

1. Verify your custom linker script and library compilation.
2. Check the linker command line and symbol visibility.
3. Inspect the linker output for errors and warnings.
4. Consult the linker documentation for additional guidance.

With patience and persistence, you’ll be able to successfully cross-compile your code with a custom linker and get your project back on track.

Good luck, and happy compiling!

Frequently Asked Question

Stuck with cross-compilation issues? We’ve got you covered!