Function std::malloc

unsigned char* malloc(size_t size)

The static helpers below call libc malloc/free directly (not std::alloc/dealloc, so no dependency on mem.sc's allocator machinery for this hot path) -- declared here rather than pulled in via std/mem.sc, matching every other .sc file in std/ that touches libc memory functions directly (see mem.sc, heap.sc, result.sc, etc., each of which declares its own copy of these same externs rather than including one another's .sc file for them).