[soulbadguy]

I am not sure if i understand the question correctly. But once collected, stack traces are just regular object that can be passed around thread as other object. It's possible that some implementation have references to some stack addresses (like for example the address of a function parameter), in which case you would need to serialize the stack trace before storing them/ moving then another thread.

[mike_hock]

> once collected, stack traces are just regular object that can be passed around thread as other object.

> It's possible that some implementation have references to some stack addresses (like for example the address of a function parameter), in which case you would need to serialize the stack trace before storing them/ moving then another thread.

So which of these two mutually exclusive options is it? As I understand it, that was the question.

[soulbadguy]

> So which of these two mutually exclusive options is it? As I understand it, that was the question.

Well the stack_entry/stack_trace object can be moved around between thread, as in the object itself is copyable and movable. However, the handle_type is implementation defined, so it might be the case that extracting the information out of the object only works on the producing thread.

[gpderetta]

As far as I understand, basic_stack trace is just a container of stacktrace_entries, which are Regular types. So the default distinct-objects type safety rules apply.

You should be able to, for example, collect the stacktace on one thread, transport it to another and print it.

[elsamuko]

When I debug multithreaded programs, the stacktrace of a breakpoint usually ends somewhere in a worker thread. What I want is that the worker thread's stacktrace part is replaced by the one who put the work into it. Kinda like the program wasn't multithreaded at all.

[gpderetta]

Ah. I guess you can capture the stack trace at task creation point, then stitch together a new stack trace by replacing the generic common prefix of your worker thread trace with the task creation one.

But you can't use the basic_stacktrace container itself as it is immutable and not constructibe from a range, so you have to roll your own. You should be able to use the stacktrace_entries though.

Most importantly, I expect that capturing a stacktrace is quite expensive, so you might not be able to do it at task creation time, and it is too late to do it later. Maybe you want this only in debug mode.

Note I haven't actually tried any if this, it is just guesswork.

[elsamuko]

Exactly this. I didn't try this, and I suppose that some low level pointer rewriting would be necessary to do this. I'm not sure if it's expensive though, maybe you can replace the pointers without resolving the stacktrace.

[gpderetta]

The problem is that to get the stacktrace of the task creation you have to traverse the stack at that point in time. You can't really do it later. And stack traversal using DWARF unwind info, for example, is neither cheap nor simple. You might have better luck if you compile with frame pointer though.

[soulbadguy]

I think what you looking for is "task tracing" not really stack tracing. The relationship between the task (like where was a task added in the thread pool) are not reflected in the stacktrace the way you want them. To address those, you need to have special handshake between the debugger and your task api. You can also instrument the "add_task" function call to log every time a task is added to you queue and do some some offline stack stiching.

[TylerGlaiel]

if you actually wanted to you could probably wrap thread to pass the stacktrace of the spawning thread into the worker thread whenever you spawn a thread and then output that upon a crash as well. the library seems pretty simple and flexible.