2008/12/16 Bram Moolenaar <b...@moolenaar.net>:
>
>
> Matt Wozniski wrote:
>
>> function! ReturnArgs(...)
>> return a:000
>> endfunction
>>
>> " Seems to work fine?
>> echo ReturnArgs(1, 2, 3)
>>
>> " SEGV
>> echo string(ReturnArgs(1, 2, 3))
>>
>> function! MakeArgsDict(...)
>> return { 'args': a:000 }
>> endfunction
>>
>> " E685 Internal Error
>> echo MakeArgsDict(1, 2, 3)
>>
>> " SEGV
>> echo string(MakeArgsDict(1, 2, 3))
>
> For it crashes a while after trying these things. Most likely the
> reference count for a:000 is wrong. Never thought of someone returning
> it...
When I debugged, I found that v_list was pointing to an invalid address,
which had been set in call_user_func() to &fc.l_varlist; This variable is
in the stack and was only valid while in call_user_func() and the functions it
may calls. Somehow, a list still refers to this address after returning from
call_user_func() so v_list points then to an invalid address.
Making variable fc static (in function call_user_func()) avoids using an
invalid address and thus avoids a crash, but it's still not the right way
to fix it.
> " Seems to work fine?
> echo ReturnArgs(1, 2, 3)
Actually, even though this appears to work, valgrind memory checker
already sees a problem there:
==23275== Invalid read of size 4
==23275== at 0x809C577: echo_string (eval.c:7232)
==23275== by 0x80AD48C: ex_echo (eval.c:19481)
==23275== by 0x80C71C6: do_one_cmd (ex_docmd.c:2622)
==23275== by 0x80C4A46: do_cmdline (ex_docmd.c:1096)
==23275== by 0x8149D7A: nv_colon (normal.c:5233)
==23275== by 0x81433FE: normal_cmd (normal.c:1200)
==23275== by 0x810678D: main_loop (main.c:1180)
==23275== by 0x81062DA: main (main.c:939)
==23275== Address 0xbef5e280 is not stack'd, malloc'd or (recently) free'd
==23275==
==23275== Invalid write of size 4
==23275== at 0x809C59D: echo_string (eval.c:7239)
==23275== by 0x80AD48C: ex_echo (eval.c:19481)
==23275== by 0x80C71C6: do_one_cmd (ex_docmd.c:2622)
==23275== by 0x80C4A46: do_cmdline (ex_docmd.c:1096)
==23275== by 0x8149D7A: nv_colon (normal.c:5233)
==23275== by 0x81433FE: normal_cmd (normal.c:1200)
==23275== by 0x810678D: main_loop (main.c:1180)
==23275== by 0x81062DA: main (main.c:939)
==23275== Address 0xbef5e280 is not stack'd, malloc'd or (recently) free'd
(etc, more errors to follow)
Line eval.c:7232 is:
7232 else if (copyID != 0 && tv->vval.v_list->lv_copyID == copyID)
7233 {
7234 *tofree = NULL;
7235 r = (char_u *)"[...]";
7236 }
'tv->vval.v_list' points to the invalid address which set as there
at line 21193:
21191 v->di_tv.v_type = VAR_LIST;
21192 v->di_tv.v_lock = VAR_FIXED;
21193 v->di_tv.vval.v_list = &fc.l_varlist;
(fc being a local var in the stack)
-- Dominique
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