feat(libc): implement functional malloc and free#37
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- Updated malloc to allocate 8 extra bytes for a size header. - Implemented free() by retrieving the original pointer and calling realloc(ptr, 0). - This enables practical memory deallocation in userland apps like Doom.
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Summary
Previously,
free()was a no-op stub, causing memory leaks in userland. This PR implements a working memory management lifecycle.Changes
mallocnow reserves an additional 8 bytes at the start of each block to store the allocation size.free(ptr)now retrieves those extra 8 bytes and triggers the kernel deallocation viarealloc(p, 0)(Syscall 20).linked_list_allocatordeallocation logic in the JOS kernel.This is a critical fix for running long-lived or memory-intensive applications in JOS.