使用 gcc/g++/gdb/valgrind 调试时的神奇数字？

Question

Microsoft's Visual C++ fills memory with 'magic numbers' if it hasn't been initialized by the programmer itself. This helps with debugging of uninitialized memory. ( In Visual Studio C++, what are the memory allocation representations? , 0xDEADBEEF vs. NULL )

Is there a similar function when using linux GNU tools (g++/gdb)?

Thanks!

Answer 1

You can override the C++ operator new to set allocations to your preferred byte pattern:

void* operator new(size_t size)
{
    void* mem = malloc(size);
    if (!mem) {
        throw std::bad_alloc();
    }
    memset(mem, 0xEE, size);
    return mem;
}

You can see the full GCC implementation here: https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/libsupc%2B%2B/new_op.cc in case you want to mirror it more closely.

That will work for anything using the default C++ allocators, but not for things using regular old malloc() . If you need to initialize memory from malloc() directly, you can override that too, but the mechanism to do it is different: you can use the linker's --wrap option to manipulate the symbol table and let you override malloc() . Then you don't need to overload operator new of course. The full approach is illustrated in an answer here: https://stackoverflow.com/a/3662951/4323