[PATCH] unwind: initialize unwind context only if given tcb is initialized

[Dmitry V. Levin]

On Thu, Apr 19, 2018 at 05:49:47PM +0900, Masatake YAMATO wrote:
> With libdw based unwinder, following warnings are reported
> when -p is passed before -k:
> 
>    $ sudo ./strace -p 1 -k
>    ./strace: dwfl_linux_proc_attach returned an error for process 0: No such file or directory
>    ...
> 
> It seems that commit 54c7792b, "Fix libunwind segfault when -p is
> passed before -k" doesn't fix the original issue.
> 
> * strace.c (init) [ENABLE_STACKTRACE]: Initialize unwind context only
> if given tcb is initialized.

Applied, thanks!

> --- a/strace.c
> +++ b/strace.c
> @@ -1783,6 +1783,8 @@ init(int argc, char *argv[])
>  
>  		unwind_init();
>  		for (tcbi = 0; tcbi < tcbtabsize; ++tcbi) {
> +			if (!tcbtab[tcbi]->pid)
> +				continue;
>  			unwind_tcb_init(tcbtab[tcbi]);
>  		}
>  	}

Apparently, we don't need this loop at all, there is no use to call
unwind_tcb_init until the tracee is actually attached.  The proper place
for unwind_tcb_init invocation is the same as for newoutf.
I've pushed a few commits to implement this change.


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