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* GDB crashes when using GDB/MI and python pretty printers in some cases
@ 2022-03-17 13:29 Jan Vrany
  2022-03-18 15:57 ` Simon Marchi
  0 siblings, 1 reply; 3+ messages in thread
From: Jan Vrany @ 2022-03-17 13:29 UTC (permalink / raw)
  To: GDB mailing list

[-- Attachment #1: Type: text/plain, Size: 3834 bytes --]

Hi Simon, others,

TL;DR: 

I'm experiencing GDB crashes with recent GDB which seem to be
caused by commit 5f8ab46. Why is that I do not know (yet). Some 
details below.

Full story:

After updating my every-day-use GDB to commit 

commit c9178f285acf19e066be8367185d52837161b0a2 (HEAD -> master, origin/master)
Author: Alan Modra <amodra@gmail.com>
Date:   Thu Mar 17 20:05:39 2022 +1030

I'm experiencing GDB to crash on assertion failure in value_copy (value.c:1731).
This is triggered when I single-step through code while having (my, custom) GDB/MI
frontent displaying local variables with python pretty printers enabled. 

For example: doing this in frontend triggers the assertion failure:

    file gdb/testsuite/outputs/gdb.python/py-prettyprint/py-prettyprint-cxx
    source gdb/testsuite/outputs/gdb.python/py-prettyprint/py-prettyprint.py
    b add_item(container*, int)
    r
    dis 1
    fin
    n
    n (few more times until it crashes)

This is the backtrace when it crashes: 

    /home/jv/Proj...atches/gdb/gdb [stopped]
      Thread  1 [stopped] "gdb"
         0 0x0000556077ADABD0 internal_error (errors.cc:51)
         1 0x00005560776148A7 value_copy (value.c:1731)
         2 0x0000556077360028 gdbpy_get_varobj_pretty_printer (py-prettyprint.c:655)
         3 0x0000556077620E60 install_default_visualizer (varobj.c:1056)
         4 0x00005560776210E9 install_new_value_visualizer (varobj.c:1127)
         5 0x00005560776218B2 install_new_value (varobj.c:1339)
         6 0x000055607761F6FB varobj_create (varobj.c:378)
         7 0x0000556077245C05 mi_cmd_var_create (mi-cmd-var.c:132)
         8 0x0000556077249F2B mi_command_mi::invoke (mi-cmds.c:58)
         9 0x0000556077264F15 mi_cmd_execute (mi-main.c:2091)
        10 0x000055607726450C captured_mi_execute_command (mi-main.c:1823)
        11 0x000055607726498A mi_execute_command (mi-main.c:1947)
        12 0x000055607724D21B mi_execute_command_wrapper (mi-interp.c:285)
        13 0x000055607724D2A4 mi_execute_command_input_handler (mi-interp.c:314)
        14 0x00005560770D7149 gdb_readline_no_editing_callback (event-top.c:878)
        15 0x00005560770D6948 stdin_event_handler (event-top.c:524)
        16 0x0000556077ADB57E gdb_wait_for_event (event-loop.cc:700)
        17 0x0000556077ADB7FB gdb_wait_for_event (event-loop.cc:596)
        18 0x0000556077ADB7FB gdb_do_one_event (event-loop.cc:237)
        19 0x000055607721BA1B start_event_loop (main.c:421)
        20 0x000055607721BB3F captured_command_loop (main.c:481)
        21 0x000055607721D535 captured_main (main.c:1351)
        22 0x000055607721D59B gdb_main (main.c:1366)
        23 0x0000556076DA7E93 main (gdb.c:32)
      Thread  2 [stopped] "gdb worker"
      Thread  3 [stopped] "gdb worker"
      Thread  4 [stopped] "gdb worker"
      Thread  5 [stopped] "gdb worker"


Unfortunately, so far I was unable to reproduce this outside my frontend. I tried
to simulate what the frontend does (see attached file), but running GDB like 


   gdb -i mi < crash-in-value_copy-reproducer.txt 


does not trigger it (arguably, the frontend issues silly / unnecessary MI commands, but still
it should not crash GDB - I would think :-). 

If I revert commit


commit 5f8ab46bc6918efb678deb5956c033e466afe301
Author: Simon Marchi <simon.marchi@polymtl.ca>
Date:   Mon Jan 31 15:57:58 2022 -0500

    gdb: constify parameter of value_copy

Everything seems to work just fine for me. I'm not at all familiar with this
part of the GDB code so I do not know whether this change is the real culprit 
or not, let alone to explain why.

I'll try to investigate further when I find more time, but in case someone brave
enough to read through this post has an idea, I'll appreciate it! 

Thanks, Jan

[-- Attachment #2: crash-in-value_copy-reproducer.txt --]
[-- Type: text/plain, Size: 14030 bytes --]


file /home/jv/Projects/gdb/users_jv_patches/gdb/testsuite/outputs/gdb.python/py-prettyprint/py-prettyprint-cxx
source /home/jv/Projects/gdb/users_jv_patches/gdb/testsuite/outputs/gdb.python/py-prettyprint/py-prettyprint.py
b add_item(container*, int)
r
23-data-list-register-names --thread 1 --frame 0
24-stack-info-depth --thread 1 100
25-data-list-register-values --thread 1 --frame 0 r
26-stack-list-frames --thread 1 0 1
27-stack-list-variables --thread 1 --frame 0 --simple-values
28-thread-info 1
29-var-create --thread 1 --frame 0 - * c
30-var-update --all-values var1
31-var-create --thread 1 --frame 0 - * val
32-var-update --all-values var2
dis 1
fin
33-data-list-register-values --thread 1 --frame 0 r
34-stack-info-depth --thread 1 100
35-stack-list-variables --thread 1 --frame 0 --simple-values
36-stack-list-frames --thread 1 0 0
37-var-create --thread 1 --frame 0 - * ss
38-var-update --all-values var3
39-var-create --thread 1 --frame 0 - * ssa
40-var-update --all-values var4
41-var-create --thread 1 --frame 0 - * arraystruct
42-var-update --all-values var5
43-var-create --thread 1 --frame 0 - * x
44-var-update --all-values var6
45-var-create --thread 1 --frame 0 - * c
46-var-update --all-values var7
47-var-create --thread 1 --frame 0 - * c2
48-var-update --all-values var8
49-var-create --thread 1 --frame 0 - * cstring
50-var-update --all-values var9
51-var-create --thread 1 --frame 0 - * nullstr
52-var-update --all-values var10
53-var-create --thread 1 --frame 0 - * nstype
54-var-update --all-values var11
55-var-create --thread 1 --frame 0 - * nstype2
56-var-update --all-values var12
57-var-create --thread 1 --frame 0 - * me
58-var-update --all-values var13
59-var-create --thread 1 --frame 0 - * ns
60-var-update --all-values var14
61-var-create --thread 1 --frame 0 - * ns2
62-var-update --all-values var15
63-var-create --thread 1 --frame 0 - * estring
64-var-update --all-values var16
65-var-create --thread 1 --frame 0 - * estring2
66-var-update --all-values var17
67-var-create --thread 1 --frame 0 - * estring3
68-var-update --all-values var18
69-exec-next
70-stack-list-variables --thread 1 --frame 0 --simple-values
71-stack-info-depth --thread 1 100
72-stack-list-frames --thread 1 0 0
73-var-create --thread 1 --frame 0 - * ss
74-var-update --all-values var19
75-var-create --thread 1 --frame 0 - * ssa
76-var-update --all-values var20
77-var-create --thread 1 --frame 0 - * arraystruct
78-var-update --all-values var21
79-var-create --thread 1 --frame 0 - * x
80-var-update --all-values var22
81-var-create --thread 1 --frame 0 - * c
82-var-update --all-values var23
83-var-create --thread 1 --frame 0 - * c2
84-var-update --all-values var24
85-var-create --thread 1 --frame 0 - * cstring
86-var-update --all-values var25
87-var-create --thread 1 --frame 0 - * nullstr
88-var-update --all-values var26
89-var-create --thread 1 --frame 0 - * nstype
90-var-update --all-values var27
91-var-create --thread 1 --frame 0 - * nstype2
92-var-update --all-values var28
93-var-create --thread 1 --frame 0 - * me
94-var-update --all-values var29
95-var-create --thread 1 --frame 0 - * ns
96-var-update --all-values var30
97-var-create --thread 1 --frame 0 - * ns2
98-var-update --all-values var31
99-var-create --thread 1 --frame 0 - * estring
100-var-update --all-values var32
101-var-create --thread 1 --frame 0 - * estring2
102-var-update --all-values var33
103-var-create --thread 1 --frame 0 - * estring3
104-var-update --all-values var34
105-exec-next
106-stack-list-variables --thread 1 --frame 0 --simple-values
107-stack-info-depth --thread 1 100
108-stack-list-frames --thread 1 0 0
109-var-create --thread 1 --frame 0 - * ss
110-var-update --all-values var35
111-var-create --thread 1 --frame 0 - * ssa
112-var-update --all-values var36
113-var-create --thread 1 --frame 0 - * arraystruct
114-var-update --all-values var37
115-var-create --thread 1 --frame 0 - * x
116-var-update --all-values var38
117-var-create --thread 1 --frame 0 - * c
118-var-update --all-values var39
119-var-create --thread 1 --frame 0 - * c2
120-var-update --all-values var40
121-var-create --thread 1 --frame 0 - * cstring
122-var-update --all-values var41
123-var-create --thread 1 --frame 0 - * nullstr
124-var-update --all-values var42
125-var-create --thread 1 --frame 0 - * nstype
126-var-update --all-values var43
127-var-create --thread 1 --frame 0 - * nstype2
128-var-update --all-values var44
129-var-create --thread 1 --frame 0 - * me
130-var-update --all-values var45
131-var-create --thread 1 --frame 0 - * ns
132-var-update --all-values var46
133-var-create --thread 1 --frame 0 - * ns2
134-var-update --all-values var47
135-var-create --thread 1 --frame 0 - * estring
136-var-update --all-values var48
137-var-create --thread 1 --frame 0 - * estring2
138-var-update --all-values var49
139-var-create --thread 1 --frame 0 - * estring3
140-var-update --all-values var50
141-exec-next
142-stack-list-variables --thread 1 --frame 0 --simple-values
143-stack-info-depth --thread 1 100
144-stack-list-frames --thread 1 0 0
145-var-create --thread 1 --frame 0 - * ss
146-var-update --all-values var51
147-var-create --thread 1 --frame 0 - * ssa
148-var-update --all-values var52
149-var-create --thread 1 --frame 0 - * arraystruct
150-var-update --all-values var53
151-var-create --thread 1 --frame 0 - * x
152-var-update --all-values var54
153-var-create --thread 1 --frame 0 - * c
154-var-update --all-values var55
155-var-create --thread 1 --frame 0 - * c2
156-var-update --all-values var56
157-var-create --thread 1 --frame 0 - * cstring
158-var-update --all-values var57
159-var-create --thread 1 --frame 0 - * nullstr
160-var-update --all-values var58
161-var-create --thread 1 --frame 0 - * nstype
162-var-update --all-values var59
163-var-create --thread 1 --frame 0 - * nstype2
164-var-update --all-values var60
165-var-create --thread 1 --frame 0 - * me
166-var-update --all-values var61
167-var-create --thread 1 --frame 0 - * ns
168-var-update --all-values var62
169-var-create --thread 1 --frame 0 - * ns2
170-var-update --all-values var63
171-var-create --thread 1 --frame 0 - * estring
172-var-update --all-values var64
173-var-create --thread 1 --frame 0 - * estring2
174-var-update --all-values var65
175-var-create --thread 1 --frame 0 - * estring3
176-var-update --all-values var66
177-exec-next
178-stack-list-variables --thread 1 --frame 0 --simple-values
179-stack-info-depth --thread 1 100
180-stack-list-frames --thread 1 0 0
181-var-create --thread 1 --frame 0 - * ss
182-var-update --all-values var67
183-var-create --thread 1 --frame 0 - * ssa
184-var-update --all-values var68
185-var-create --thread 1 --frame 0 - * arraystruct
186-var-update --all-values var69
187-var-create --thread 1 --frame 0 - * x
188-var-update --all-values var70
189-var-create --thread 1 --frame 0 - * c
190-var-update --all-values var71
191-var-create --thread 1 --frame 0 - * c2
192-var-update --all-values var72
193-var-create --thread 1 --frame 0 - * cstring
194-var-update --all-values var73
195-var-create --thread 1 --frame 0 - * nullstr
196-var-update --all-values var74
197-var-create --thread 1 --frame 0 - * nstype
198-var-update --all-values var75
199-var-create --thread 1 --frame 0 - * nstype2
200-var-update --all-values var76
201-var-create --thread 1 --frame 0 - * me
202-var-update --all-values var77
203-var-create --thread 1 --frame 0 - * ns
204-var-update --all-values var78
205-var-create --thread 1 --frame 0 - * ns2
206-var-update --all-values var79
207-var-create --thread 1 --frame 0 - * estring
208-var-update --all-values var80
209-var-create --thread 1 --frame 0 - * estring2
210-var-update --all-values var81
211-var-create --thread 1 --frame 0 - * estring3
212-var-update --all-values var82
213-exec-next
214-stack-list-variables --thread 1 --frame 0 --simple-values
215-stack-info-depth --thread 1 100
216-stack-list-frames --thread 1 0 0
217-var-create --thread 1 --frame 0 - * ss
218-var-update --all-values var83
219-var-create --thread 1 --frame 0 - * ssa
220-var-update --all-values var84
221-var-create --thread 1 --frame 0 - * arraystruct
222-var-update --all-values var85
223-var-create --thread 1 --frame 0 - * x
224-var-update --all-values var86
225-var-create --thread 1 --frame 0 - * c
226-var-update --all-values var87
227-var-create --thread 1 --frame 0 - * c2
228-var-update --all-values var88
229-var-create --thread 1 --frame 0 - * cstring
230-var-update --all-values var89
231-var-create --thread 1 --frame 0 - * nullstr
232-var-update --all-values var90
233-var-create --thread 1 --frame 0 - * nstype
234-var-update --all-values var91
235-var-create --thread 1 --frame 0 - * nstype2
236-var-update --all-values var92
237-var-create --thread 1 --frame 0 - * me
238-var-update --all-values var93
239-var-create --thread 1 --frame 0 - * ns
240-var-update --all-values var94
241-var-create --thread 1 --frame 0 - * ns2
242-var-update --all-values var95
243-var-create --thread 1 --frame 0 - * estring
244-var-update --all-values var96
245-var-create --thread 1 --frame 0 - * estring2
246-var-update --all-values var97
247-var-create --thread 1 --frame 0 - * estring3
248-var-update --all-values var98
249-exec-next
250-stack-list-variables --thread 1 --frame 0 --simple-values
251-stack-info-depth --thread 1 100
252-stack-list-frames --thread 1 0 0
253-var-create --thread 1 --frame 0 - * ss
254-var-update --all-values var99
255-var-create --thread 1 --frame 0 - * ssa
256-var-update --all-values var100
257-var-create --thread 1 --frame 0 - * arraystruct
258-var-update --all-values var101
259-var-create --thread 1 --frame 0 - * x
260-var-update --all-values var102
261-var-create --thread 1 --frame 0 - * c
262-var-update --all-values var103
263-var-create --thread 1 --frame 0 - * c2
264-var-update --all-values var104
265-var-create --thread 1 --frame 0 - * cstring
266-var-update --all-values var105
267-var-create --thread 1 --frame 0 - * nullstr
268-var-update --all-values var106
269-var-create --thread 1 --frame 0 - * nstype
270-var-update --all-values var107
271-var-create --thread 1 --frame 0 - * nstype2
272-var-update --all-values var108
273-var-create --thread 1 --frame 0 - * me
274-var-update --all-values var109
275-var-create --thread 1 --frame 0 - * ns
276-var-update --all-values var110
277-var-create --thread 1 --frame 0 - * ns2
278-var-update --all-values var111
279-var-create --thread 1 --frame 0 - * estring
280-var-update --all-values var112
281-var-create --thread 1 --frame 0 - * estring2
282-var-update --all-values var113
283-var-create --thread 1 --frame 0 - * estring3
284-var-update --all-values var114
285-exec-next
286-stack-list-variables --thread 1 --frame 0 --simple-values
287-stack-info-depth --thread 1 100
288-stack-list-frames --thread 1 0 0
289-var-create --thread 1 --frame 0 - * ss
290-var-update --all-values var115
291-var-create --thread 1 --frame 0 - * ssa
292-var-update --all-values var116
293-var-create --thread 1 --frame 0 - * arraystruct
294-var-update --all-values var117
295-var-create --thread 1 --frame 0 - * x
296-var-update --all-values var118
297-var-create --thread 1 --frame 0 - * c
298-var-update --all-values var119
299-var-create --thread 1 --frame 0 - * c2
300-var-update --all-values var120
301-var-create --thread 1 --frame 0 - * cstring
302-var-update --all-values var121
303-var-create --thread 1 --frame 0 - * nullstr
304-var-update --all-values var122
305-var-create --thread 1 --frame 0 - * nstype
306-var-update --all-values var123
307-var-create --thread 1 --frame 0 - * nstype2
308-var-update --all-values var124
309-var-create --thread 1 --frame 0 - * me
310-var-update --all-values var125
311-var-create --thread 1 --frame 0 - * ns
312-var-update --all-values var126
313-var-create --thread 1 --frame 0 - * ns2
314-var-update --all-values var127
315-var-create --thread 1 --frame 0 - * estring
316-var-update --all-values var128
317-var-create --thread 1 --frame 0 - * estring2
318-var-update --all-values var129
319-var-create --thread 1 --frame 0 - * estring3
320-var-update --all-values var130
321-exec-next
322-stack-list-variables --thread 1 --frame 0 --simple-values
323-stack-info-depth --thread 1 100
324-stack-list-frames --thread 1 0 0
325-var-create --thread 1 --frame 0 - * ss
326-var-update --all-values var131
327-var-create --thread 1 --frame 0 - * ssa
328-var-update --all-values var132
329-var-create --thread 1 --frame 0 - * arraystruct
330-var-update --all-values var133
331-var-create --thread 1 --frame 0 - * x
332-var-update --all-values var134
333-var-create --thread 1 --frame 0 - * c
334-var-update --all-values var135
335-var-create --thread 1 --frame 0 - * c2
336-var-update --all-values var136
337-var-create --thread 1 --frame 0 - * cstring
338-var-update --all-values var137
339-var-create --thread 1 --frame 0 - * nullstr
340-var-update --all-values var138
341-var-create --thread 1 --frame 0 - * nstype
342-var-update --all-values var139
343-var-create --thread 1 --frame 0 - * nstype2
344-var-update --all-values var140
345-var-create --thread 1 --frame 0 - * me
346-var-update --all-values var141
347-var-create --thread 1 --frame 0 - * ns
348-var-update --all-values var142
349-var-create --thread 1 --frame 0 - * ns2
350-var-update --all-values var143
351-var-create --thread 1 --frame 0 - * estring
352-var-update --all-values var144
353-var-create --thread 1 --frame 0 - * estring2
354-var-update --all-values var145
355-var-create --thread 1 --frame 0 - * estring3
356-var-update --all-values var146
357-exec-next
358-data-list-register-values --thread 1 --frame 0 r
359-gdb-show directories
360-stack-info-depth --thread 1 100
361-stack-list-variables --thread 1 --frame 0 --simple-values
362-stack-list-frames --thread 1 0 1
363-var-create --thread 1 --frame 0 - * main
364-var-update --all-values var147
365-var-create --thread 1 --frame 0 - * argc
366-var-update --all-values var148
367-var-create --thread 1 --frame 0 - * argv
368-var-update --all-values var149
369-var-create --thread 1 --frame 0 - * init
-exec-next

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2022-03-22 12:31 UTC | newest]

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2022-03-17 13:29 GDB crashes when using GDB/MI and python pretty printers in some cases Jan Vrany
2022-03-18 15:57 ` Simon Marchi
2022-03-22 12:31   ` Jan Vrany

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