FreeJoy Custom Firmware Works on Windows but Fails in Linux Configurator #270

I discovered that the FreeJoy firmware compiled with arm-none-eabi-gcc on Linux was causing problems, while the same project worked correctly when compiled with the Keil ARM compiler. After several tests, I concluded that the issue is related to compiler compatibility and version differences.

The original FreeJoy project appears to have been developed and optimized for the Keil ARM Compiler (ARMCC), especially version 5.x, which handles some optimizations, memory alignment, and compiler-specific extensions differently from modern GCC toolchains. When I used the compiler version included in Keil, the firmware behaved correctly again.

The GNU ARM Embedded Toolchain (arm-none-eabi-gcc) may generate different code depending on the GCC version, optimization flags, ABI compatibility, and handling of volatile variables or packed structures. Some embedded projects, especially older STM32 projects, rely on behavior that is compiler-specific.

Because of this, compiling FreeJoy with a newer GCC version on Linux can introduce unexpected runtime issues, while compiling with the original Keil ARM compiler version maintains compatibility with the project's original assumptions and generated binary behavior.