How to prevent inclusion of C library destructors and atexit()?

Question

Using arm-none-eabi-gcc for Cortex-M4 (baremetal application), the code for malloc is also emitted even though I never use malloc in my code.

S

Answer 1

In an environment with limited memory such as the Cortex M4, another option is to use newlib-nano. It provides a __register_exitproc() that is weakly linked. Therefore it is easy to override with your own empty function that avoids calling malloc(). This will have the additional benefit of removing __call_exitprocs() from your binary as well.

• Add the flag --specs=nano.specs to your compiler and linker options.
• Create the following function somewhere in your compiled code: void __register_exitproc(void) { }

Note that this will prevent destructors being called for static instances of classes. This seems appropriate in your example.

See the comments in the newlib source for more details.