[lldb-dev] How to tell if an address belongs to the heap?

[Pavel Labath via lldb-dev]

In general, getting this kind of information is pretty hard, so lldb does
not offer you an out-of-the-box solution for it, but it does give you tools
which you can use to approximate that.

If I wanted to do something like this, the first thing I'd try to do is run
"image lookup -a 0xaddr". If this doesn't return anything then the address
does not correspond to any known module. This rules out code, global
variables, and similar. Then you can run through all of the threads and do
a "memory region $SP", which will give you bounds of the memory allocation
around the stack pointer. If your address is in one of these ranges, then
it's a stack address. Otherwise, it's probably heap (though you can never
be 100% sure of that).

However, it's not fully clear to me what it is that you're trying to do
here. Maybe if you explain the higher level problem that you're trying to
solve, we can come up with a better solution.

pl

On Thu, 6 Feb 2020 at 07:40, Vangelis Tsiatsianas via lldb-dev <
lldb-dev at lists.llvm.org> wrote:

> Hi everyone,
>
> I am looking for a way to tell whether a memory address belongs to the
> heap or not.
>
> In other words, I would like to make sure that the address does not reside
> within any stack frame (even if the stack of the thread has been allocated
> in the heap) and that it’s not a global variable or instruction.
>
> Checking whether it is a valid or correctly allocated address or a
> memory-mapped file or register is not a goal, so accessing it in order to
> decide, at the risk of causing a segmentation fault, is an accepted
> solution.
>
> I have been thinking of manually checking the address against the
> boundaries of each active stack frame, the start and end of the instruction
> segment and the locations of all global variables.
>
> However, I would like to ask where there are better ways to approach this
> problem in LLDB.
>
> Thank you very much, advance! 🙂
>
>
> ― Vangelis
>
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