Subject: Re: bug#23424: 25.0.93; error in process sentinel with Melpa added to package-archives

From: Kaushal Modi <[email-masked]>
Date: Mon, 02 May 2016 17:22:05 +0000

>
> This is your "Debugging Emacs 101", lesson 1:
>
> A breakpoint in Fsignal is frequently hit because some error is thrown
> which Emacs will catch and ignore, but the debugger gets to see it
> first.  To see whether this is the signal you are after (if you don't
> already know), do this:
>
>   (gdb) p error_symbol
>   (gdb) xsymbol
>
> The last command should display the Lisp name of the signal.  Crystal
> ball here says you will see "void-variable", which is not the signal
> you want.  So now make the breakpoint conditional:
>
>   (gdb) condition 3 error_symbol != 41328
>   (gdb) c
>
> and see what other signal is thrown.  I had a couple of other
> unrelated signals (which happened once each, so I didn't feel like
> making the condition more complex), and finally you will get your
> expected "end-of-file" error.  Then look around; the Lisp backtrace
> should be the first thing to look at.
>

Thanks for that quick intro to setting conditional breakpoints.

 I did

(gdb) condition 3 error_symbol!=<num1> && error_symbol!=<num2> && ..

and looks like that worked.

But it looks like I have a different backtrace than the one you got.

(gdb) p error_symbol
$3 = 49824
(gdb) xsymbol
$4 = (struct Lisp_Symbol *) 0xc87bd0 <lispsym+49824>
"void-variable"
(gdb) condition 3 error_symbol!=41328 && error_symbol!=49824
(gdb) c
Continuing.

Breakpoint 3, Fsignal (error_symbol=19056, data=16197139) at eval.c:1471
1471        = (NILP (error_symbol) ? Fcar (data) : error_symbol);
(gdb) p error_symbol
$5 = 19056
(gdb) xsymbol
$6 = (struct Lisp_Symbol *) 0xc803a0 <lispsym+19056>
"error"
(gdb) bt
#0  Fsignal (error_symbol=19056, data=16197139) at eval.c:1471
#1  0x00000000005f631a in Ffuncall (nargs=3, args=0x7fffffff6430) at
eval.c:2696
#2  0x000000000063c073 in exec_byte_code (bytestr=9618644, vector=9618677,
maxdepth=26, args_template=514, nargs=2, args=0x7fffffff6970) at
bytecode.c:880
#3  0x00000000005f6b6c in funcall_lambda (fun=9618597, nargs=2,
arg_vector=0x7fffffff6970) at eval.c:2855
#4  0x00000000005f6568 in Ffuncall (nargs=3, args=0x7fffffff6968) at
eval.c:2742
#5  0x000000000063c073 in exec_byte_code (bytestr=26216724,
vector=26182181, maxdepth=18, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#6  0x00000000005f6ea8 in funcall_lambda (fun=26182285, nargs=2,
arg_vector=0x18f8225) at eval.c:2921
#7  0x00000000005f6568 in Ffuncall (nargs=3, args=0x7fffffff6e98) at
eval.c:2742
#8  0x000000000063c073 in exec_byte_code (bytestr=26203300,
vector=26180981, maxdepth=22, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#9  0x00000000005f6ea8 in funcall_lambda (fun=26181189, nargs=1,
arg_vector=0x18f7d75) at eval.c:2921
#10 0x00000000005f6568 in Ffuncall (nargs=2, args=0x7fffffff73d8) at
eval.c:2742
#11 0x000000000063c073 in exec_byte_code (bytestr=25712436,
vector=20655013, maxdepth=26, args_template=1026, nargs=1,
args=0x7fffffff7918) at bytecode.c:880
#12 0x00000000005f6b6c in funcall_lambda (fun=24354509, nargs=1,
arg_vector=0x7fffffff7910) at eval.c:2855
#13 0x00000000005f6568 in Ffuncall (nargs=2, args=0x7fffffff7908) at
eval.c:2742
#14 0x000000000063c073 in exec_byte_code (bytestr=17397476,
vector=21453909, maxdepth=10, args_template=2, nargs=0,
args=0x7fffffff7e40) at bytecode.c:880
#15 0x00000000005f6b6c in funcall_lambda (fun=20671589, nargs=0,
arg_vector=0x7fffffff7e40) at eval.c:2855
#16 0x00000000005f6568 in Ffuncall (nargs=1, args=0x7fffffff7e38) at
eval.c:2742
#17 0x000000000063c073 in exec_byte_code (bytestr=14902196,
vector=21523493, maxdepth=22, args_template=1026, nargs=1,
args=0x7fffffff8448) at bytecode.c:880
#18 0x00000000005f6b6c in funcall_lambda (fun=21523645, nargs=1,
arg_vector=0x7fffffff8440) at eval.c:2855
#19 0x00000000005f6568 in Ffuncall (nargs=2, args=0x7fffffff8438) at
eval.c:2742
#20 0x00000000005ee638 in Ffuncall_interactively (nargs=2,
args=0x7fffffff8438) at callint.c:252
#21 0x00000000005f61e8 in Ffuncall (nargs=3, args=0x7fffffff8430) at
eval.c:2673
#22 0x00000000005f09be in Fcall_interactively (function=5444288,
record_flag=5289200, keys=13400757) at callint.c:840
#23 0x00000000005f6355 in Ffuncall (nargs=4, args=0x7fffffff8758) at
eval.c:2700
#24 0x000000000063c073 in exec_byte_code (bytestr=10409484,
vector=10409517, maxdepth=54, args_template=4102, nargs=2,
args=0x7fffffff8cd8) at bytecode.c:880
#25 0x00000000005f6b6c in funcall_lambda (fun=10409437, nargs=2,
arg_vector=0x7fffffff8cc8) at eval.c:2855
#26 0x00000000005f6568 in Ffuncall (nargs=3, args=0x7fffffff8cc0) at
eval.c:2742
#27 0x000000000063c073 in exec_byte_code (bytestr=10408684,
vector=10408717, maxdepth=62, args_template=3078, nargs=3,
args=0x7fffffff9318) at bytecode.c:880
#28 0x00000000005f6b6c in funcall_lambda (fun=10408629, nargs=3,
arg_vector=0x7fffffff9300) at eval.c:2855
#29 0x00000000005f6568 in Ffuncall (nargs=4, args=0x7fffffff92f8) at
eval.c:2742
#30 0x00000000005ee638 in Ffuncall_interactively (nargs=4,
args=0x7fffffff92f8) at callint.c:252
#31 0x00000000005f61e8 in Ffuncall (nargs=5, args=0x7fffffff92f0) at
eval.c:2673
#32 0x00000000005f576f in Fapply (nargs=3, args=0x7fffffff93e0) at
eval.c:2321
#33 0x00000000005eeab0 in Fcall_interactively (function=560928,
record_flag=0, keys=13400757) at callint.c:389
#34 0x00000000005f6355 in Ffuncall (nargs=4, args=0x7fffffff9668) at
eval.c:2700
#35 0x000000000063c073 in exec_byte_code (bytestr=10409484,
vector=10409517, maxdepth=54, args_template=4102, nargs=1,
args=0x7fffffff9bc0) at bytecode.c:880
#36 0x00000000005f6b6c in funcall_lambda (fun=10409437, nargs=1,
arg_vector=0x7fffffff9bb8) at eval.c:2855
#37 0x00000000005f6568 in Ffuncall (nargs=2, args=0x7fffffff9bb0) at
eval.c:2742
#38 0x00000000005f5d10 in call1 (fn=14784, arg1=560928) at eval.c:2552
#39 0x000000000055ac58 in command_loop_1 () at keyboard.c:1471
#40 0x00000000005f2f86 in internal_condition_case (bfun=0x55a49f
<command_loop_1>, handlers=19056, hfun=0x559c89 <cmd_error>) at eval.c:1309
#41 0x000000000055a1a7 in command_loop_2 (ignore=0) at keyboard.c:1099
#42 0x00000000005f28a6 in internal_catch (tag=46224, func=0x55a17e
<command_loop_2>, arg=0) at eval.c:1074
#43 0x000000000055a147 in command_loop () at keyboard.c:1078
#44 0x0000000000559858 in recursive_edit_1 () at keyboard.c:684
#45 0x00000000005599eb in Frecursive_edit () at keyboard.c:755
#46 0x00000000005578aa in main (argc=2, argv=0x7fffffffa068) at emacs.c:1606

Lisp Backtrace:
"signal" (0xffff6438)
"error" (0xffff6970)
"epg-check-configuration" (0xffff6ea0)
"epg-find-configuration" (0xffff73e0)
"package-refresh-contents" (0xffff7910)
"package-menu-refresh" (0xffff7e40)
"list-packages" (0xffff8440)
"funcall-interactively" (0xffff8438)
"call-interactively" (0xffff8760)
"command-execute" (0xffff8cc8)
"execute-extended-command" (0xffff9300)
"funcall-interactively" (0xffff92f8)
"call-interactively" (0xffff9670)
"command-execute" (0xffff9bb8)
(gdb)

-- 

-- 
Kaushal Modi