Coding Spirit

一位程序员,比较帅的那种

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GCC: --wrap option

GNU linker provides an --wrap option which can help developer replace symbols easily.

In man ld:

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--wrap=symbol
Use a wrapper function for symbol. Any undefined reference to symbol will be resolved to
"__wrap_symbol". Any undefined reference to "__real_symbol" will be resolved to symbol.

This can be used to provide a wrapper for a system function. The wrapper function should
be called "__wrap_symbol". If it wishes to call the system function, it should call
"__real_symbol".

One of user scenario is when developer is trying to analyze heap usage with customized malloc and free(i.e. using memory pool):

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void * __wrap_malloc (size_t size)
{
printf ("malloc called with %zu\n", size);
return memory_pool_malloc(size);
}
//Same for free, realloc and calloc

Then link with option --wrap,malloc --wrap,free --wrap,realloc --wrap,calloc. If user want to mix customized malloc and system malloc, they can call __real_malloc when they want to call the system malloc.