Compiling a custom malloc

Question

I have written a custom library which implements malloc/calloc/realloc/free using the standard C prototypes, and I figured out how to compile it to an so. I want to test the

Answer 1

Functions that you are trying to replace are standard C functions, not macros, not system calls. So you have to simply give your functions the same names and compile them into a shared library.

Then, use LD_PRELOAD to pre-load your library before binary starts. Since all addresses are resolved once, linker will figure out addresses of your functions and remember their names and will not look for them in standard library later.

This approach might not work if your program is linked with the standard runtime statically. Also, it will not work on Mac OS X as there is another API for interpolation.

In Linux, for example, in order for your functions to co-exist (i.e. if you want to use system malloc in your own implementation of malloc), you have to open the standard library manually using dlopen, look up functions you need there using dlsym and call them later by address.