bug#24358: 25.1.50;

[Sam Halliday]

I've also been experiencing this bug and I raised a thread about it on
the ArchLinux forums:
https://bbs.archlinux.org/viewtopic.php?pid=1662221

I have built the emacs-25 branch with debugging flags "-O0 -gdwarf-4
-g3" as advised.

I can (unreliably) reproduce by typing `M-x ensime` and it seems like
emacs is crashing when loading the .ensime file, which is an
s-expression file that is loaded as data in
https://github.com/ensime/ensime-emacs/blob/master/ensime-config.el#L153-L168
(actually if anybody knows of a more efficient way to load the file,
I'd be keen to update our code, I'm a maintainer).  The exact file
that it is apparently performing the re_search within is
https://gist.github.com/fommil/d906918819cd2632e9864842e1d59b57

I get this on segfault

=====
Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
0x00000000005bdd06 in re_search_2 (bufp=0xc49b30 <searchbufs+3632>,
str1=0x56e5508 <error: Cannot access memory at address 0x56e5508>,
size1=0,
    str2=0x56e5508 <error: Cannot access memory at address 0x56e5508>,
size2=65565, startpos=646, range=509, regs=0xc4a930 <search_regs>,
stop=1155)
    at regex.c:4464
4464      int len = BYTES_BY_CHAR_HEAD (*p);
=====

and a bt on the core follows (sorry, huge dump).

Could somebody please let me know how to dig into 0x56e5508 (if
relevant)? I have never used gdb in anger.



#0  0x00000000005bdd06 in re_search_2 (bufp=0xc49b30
<searchbufs+3632>, str1=0x56e5508 <error: Cannot access memory at
address 0x56e5508>, size1=0, str2=0x56e5508 <error: Cannot access
memory at address 0x56e5508>, size2=65565, startpos=646, range=509,
regs=0xc4a930 <search_regs>, stop=1155) at regex.c:4464
#1  0x00000000005acc42 in search_buffer (string=14269316, pos=624,
pos_byte=624, lim=1156, lim_byte=1156, n=1, RE=1, trt=0,
inverse_trt=0, posix=false)
    at search.c:1265
#2  0x00000000005ac4b8 in search_command (string=14269316, bound=4626,
noerror=44544, count=0, direction=1, RE=1, posix=false) at
search.c:1058
#3  0x00000000005b00df in Fre_search_forward (regexp=14269316,
bound=4626, noerror=44544, count=0) at search.c:2264
#4  0x00000000005eec29 in Ffuncall (nargs=4, args=0x7ffffffefad8) at eval.c:2709
#5  0x0000000000630d52 in exec_byte_code (bytestr=10818516,
vector=10818549, maxdepth=38, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#6  0x00000000005ef6f1 in funcall_lambda (fun=10818469, nargs=3,
arg_vector=0xa513f5 <pure+1329237>) at eval.c:2928
#7  0x00000000005eedfa in Ffuncall (nargs=4, args=0x7fffffff0028) at eval.c:2747
#8  0x0000000000630d52 in exec_byte_code (bytestr=10813244,
vector=10813277, maxdepth=22, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#9  0x00000000005ef6f1 in funcall_lambda (fun=10813165, nargs=3,
arg_vector=0xa4ff5d <pure+1323965>) at eval.c:2928
#10 0x00000000005eedfa in Ffuncall (nargs=4, args=0x7fffffff0558) at eval.c:2747
#11 0x0000000000630d52 in exec_byte_code (bytestr=10810988,
vector=10811021, maxdepth=18, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#12 0x00000000005ef6f1 in funcall_lambda (fun=10810877, nargs=2,
arg_vector=0xa4f68d <pure+1321709>) at eval.c:2928
#13 0x00000000005eedfa in Ffuncall (nargs=3, args=0x7fffffff0a90) at eval.c:2747
#14 0x0000000000630d52 in exec_byte_code (bytestr=10832908,
vector=50228949, maxdepth=42, args_template=1030, nargs=1,
args=0x7fffffff1190) at bytecode.c:880
#15 0x00000000005ef3b5 in funcall_lambda (fun=50229021, nargs=1,
arg_vector=0x7fffffff1188) at eval.c:2862
#16 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffff1180) at eval.c:2747
#17 0x00000000005ee202 in run_hook_wrapped_funcall (nargs=2,
args=0x7fffffff1180) at eval.c:2433
#18 0x00000000005ee459 in run_hook_with_args (nargs=2,
args=0x7fffffff1180, funcall=0x5ee1b6 <run_hook_wrapped_funcall>) at
eval.c:2514
#19 0x00000000005ee251 in Frun_hook_wrapped (nargs=2,
args=0x7fffffff1180) at eval.c:2448
#20 0x00000000005eea79 in Ffuncall (nargs=3, args=0x7fffffff1178) at eval.c:2678
#21 0x0000000000630d52 in exec_byte_code (bytestr=10832780,
vector=10832813, maxdepth=78, args_template=2058, nargs=2,
args=0x7fffffff1730) at bytecode.c:880
#22 0x00000000005ef3b5 in funcall_lambda (fun=10832733, nargs=2,
arg_vector=0x7fffffff1720) at eval.c:2862
#23 0x00000000005eedfa in Ffuncall (nargs=3, args=0x7fffffff1718) at eval.c:2747
#24 0x0000000000630d52 in exec_byte_code (bytestr=10833076,
vector=10833109, maxdepth=110, args_template=2050, nargs=2,
args=0x7fffffff1ce8)
    at bytecode.c:880
#25 0x00000000005ef3b5 in funcall_lambda (fun=10833029, nargs=2,
arg_vector=0x7fffffff1cd8) at eval.c:2862
#26 0x00000000005eedfa in Ffuncall (nargs=3, args=0x7fffffff1cd0) at eval.c:2747
#27 0x0000000000630d52 in exec_byte_code (bytestr=10832452,
vector=10832485, maxdepth=50, args_template=1030, nargs=1,
args=0x7fffffff22a0) at bytecode.c:880
#28 0x00000000005ef3b5 in funcall_lambda (fun=10832405, nargs=1,
arg_vector=0x7fffffff2298) at eval.c:2862
#29 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffff2290) at eval.c:2747
#30 0x00000000005ebc6f in internal_condition_case_n (bfun=0x5ee7f9
<Ffuncall>, nargs=2, args=0x7fffffff2290, handlers=44544, hfun=
    0x43cbff <safe_eval_handler>) at eval.c:1394
#31 0x000000000043ce50 in safe__call (inhibit_quit=false, nargs=2,
func=9481216, ap=0x7fffffff2350) at xdisp.c:2558
#32 0x000000000043cf43 in safe_call (nargs=2, func=9481216) at xdisp.c:2574
#33 0x000000000043cf7d in safe_call1 (fn=9481216, arg=2498) at xdisp.c:2585
#34 0x000000000043fecc in handle_fontified_prop (it=0x7fffffff3af0) at
xdisp.c:3805
#35 0x000000000043eec7 in handle_stop (it=0x7fffffff3af0) at xdisp.c:3371
#36 0x000000000044bd29 in next_element_from_buffer (it=0x7fffffff3af0)
at xdisp.c:8322
#37 0x0000000000448302 in get_next_display_element (it=0x7fffffff3af0)
at xdisp.c:6922
#38 0x000000000046ec93 in display_line (it=0x7fffffff3af0) at xdisp.c:20598
#39 0x000000000046450e in try_window (window=20368437, pos=...,
flags=1) at xdisp.c:17247
#40 0x0000000000461937 in redisplay_window (window=20368437,
just_this_one_p=false) at xdisp.c:16696
#41 0x000000000045a803 in redisplay_window_0 (window=20368437) at xdisp.c:14487
#42 0x00000000005ebb1d in internal_condition_case_1 (bfun=0x45a7c1
<redisplay_window_0>, arg=20368437, handlers=13659203, hfun=0x45a789
<redisplay_window_error>) at eval.c:1338
#43 0x000000000045a766 in redisplay_windows (window=20368437) at xdisp.c:14467
#44 0x0000000000459893 in redisplay_internal () at xdisp.c:14027
#45 0x000000000045a183 in redisplay_preserve_echo_area (from_where=13)
at xdisp.c:14320
#46 0x0000000000635b28 in Fdelete_process (process=50226429) at process.c:873
#47 0x00000000005eeb78 in Ffuncall (nargs=2, args=0x7fffffff8b48) at eval.c:2698
#48 0x0000000000630d52 in exec_byte_code (bytestr=16680580,
vector=19382253, maxdepth=18, args_template=2058, nargs=2,
args=0x7fffffff90a0) at bytecode.c:880
#49 0x00000000005ef3b5 in funcall_lambda (fun=48360773, nargs=2,
arg_vector=0x7fffffff9090) at eval.c:2862
#50 0x00000000005eedfa in Ffuncall (nargs=3, args=0x7fffffff9088) at eval.c:2747
#51 0x0000000000630d52 in exec_byte_code (bytestr=54486340,
vector=47296317, maxdepth=30, args_template=1030, nargs=1,
args=0x7fffffff95b8) at bytecode.c:880
#52 0x00000000005ef3b5 in funcall_lambda (fun=47296397, nargs=1,
arg_vector=0x7fffffff95b0) at eval.c:2862
#53 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffff95a8) at eval.c:2747
#54 0x0000000000630d52 in exec_byte_code (bytestr=54504036,
vector=47287597, maxdepth=10, args_template=2, nargs=0,
args=0x7fffffff9ad0) at bytecode.c:880
#55 0x00000000005ef3b5 in funcall_lambda (fun=47287653, nargs=0,
arg_vector=0x7fffffff9ad0) at eval.c:2862
#56 0x00000000005eedfa in Ffuncall (nargs=1, args=0x7fffffff9ac8) at eval.c:2747
#57 0x0000000000630d52 in exec_byte_code (bytestr=54527172,
vector=47283725, maxdepth=6, args_template=2, nargs=0,
args=0x7fffffffa080) at bytecode.c:880
#58 0x00000000005ef3b5 in funcall_lambda (fun=47283773, nargs=0,
arg_vector=0x7fffffffa080) at eval.c:2862
#59 0x00000000005eedfa in Ffuncall (nargs=1, args=0x7fffffffa078) at eval.c:2747
#60 0x00000000005ee058 in funcall_nil (nargs=1, args=0x7fffffffa078)
at eval.c:2337
#61 0x00000000005ee459 in run_hook_with_args (nargs=1,
args=0x7fffffffa078, funcall=0x5ee035 <funcall_nil>) at eval.c:2514
#62 0x00000000005ee0df in Frun_hook_with_args (nargs=1,
args=0x7fffffffa078) at eval.c:2379
#63 0x00000000005ee4b8 in run_hook (hook=41424256) at eval.c:2527
#64 0x000000000057a033 in Fkill_buffer (buffer_or_name=37882885) at
buffer.c:1680
#65 0x00000000005eeb78 in Ffuncall (nargs=2, args=0x7fffffffa228) at eval.c:2698
#66 0x0000000000630d52 in exec_byte_code (bytestr=52539684,
vector=29921029, maxdepth=22, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#67 0x00000000005ef6f1 in funcall_lambda (fun=29921173, nargs=1,
arg_vector=0x1c88f05) at eval.c:2928
#68 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffffa758) at eval.c:2747
#69 0x0000000000630d52 in exec_byte_code (bytestr=41688580,
vector=54799629, maxdepth=34, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#70 0x00000000005ef6f1 in funcall_lambda (fun=54799973, nargs=1,
arg_vector=0x3442d0d) at eval.c:2928
#71 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffffaca8) at eval.c:2747
#72 0x0000000000630d52 in exec_byte_code (bytestr=41686276,
vector=54799229, maxdepth=26, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#73 0x00000000005ef6f1 in funcall_lambda (fun=54799437, nargs=1,
arg_vector=0x3442b7d) at eval.c:2928
#74 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffffb1e8) at eval.c:2747
#75 0x0000000000630d52 in exec_byte_code (bytestr=41687076,
vector=54799477, maxdepth=10, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#76 0x00000000005ef6f1 in funcall_lambda (fun=54799517, nargs=1,
arg_vector=0x3442c75) at eval.c:2928
#77 0x00000000005ef137 in apply_lambda (fun=54799517, args=43886963,
count=24) at eval.c:2799
#78 0x00000000005ed9d6 in eval_sub (form=43886947) at eval.c:2216
#79 0x00000000005e9efc in Fprogn (body=43886931) at eval.c:431
#80 0x00000000005ef660 in funcall_lambda (fun=43886899, nargs=1,
arg_vector=0x7fffffffb980) at eval.c:2921
#81 0x00000000005eeecb in Ffuncall (nargs=2, args=0x7fffffffb978) at eval.c:2759
#82 0x0000000000630d52 in exec_byte_code (bytestr=22881828,
vector=44171061, maxdepth=22, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#83 0x00000000005ef6f1 in funcall_lambda (fun=44171189, nargs=3,
arg_vector=0x2a1ff35) at eval.c:2928
#84 0x00000000005eedfa in Ffuncall (nargs=4, args=0x7fffffffbea8) at eval.c:2747
#85 0x0000000000630d52 in exec_byte_code (bytestr=39202884,
vector=58046421, maxdepth=30, args_template=0, nargs=0, args=0x0) at
bytecode.c:880
#86 0x0000000000630153 in Fbyte_code (bytestr=39202884,
vector=58046421, maxdepth=30) at bytecode.c:449
#87 0x00000000005ed82a in eval_sub (form=54684739) at eval.c:2177
#88 0x00000000005eb9f7 in internal_lisp_condition_case (var=9356672,
bodyform=54684739, handlers=54684499) at eval.c:1285
#89 0x0000000000631ee7 in exec_byte_code (bytestr=39203140,
vector=58046541, maxdepth=14, args_template=0, nargs=0, args=0x0) at
bytecode.c:1119
#90 0x00000000005ef6f1 in funcall_lambda (fun=58046597, nargs=0,
arg_vector=0x375b84d) at eval.c:2928
#91 0x00000000005eedfa in Ffuncall (nargs=1, args=0x7fffffffcb68) at eval.c:2747
#92 0x00000000005e7151 in Ffuncall_interactively (nargs=1,
args=0x7fffffffcb68) at callint.c:252
#93 0x00000000005eea79 in Ffuncall (nargs=2, args=0x7fffffffcb60) at eval.c:2678
#94 0x00000000005edca2 in Fapply (nargs=3, args=0x7fffffffcb60) at eval.c:2279
#95 0x00000000005e75c9 in Fcall_interactively (function=1641232,
record_flag=5302080, keys=13460885) at callint.c:389
#96 0x00000000005eebe6 in Ffuncall (nargs=4, args=0x7fffffffcde8) at eval.c:2705
#97 0x0000000000630d52 in exec_byte_code (bytestr=10383612,
vector=10383645, maxdepth=54, args_template=4102, nargs=2,
args=0x7fffffffd368) at bytecode.c:880
#98 0x00000000005ef3b5 in funcall_lambda (fun=10383565, nargs=2,
arg_vector=0x7fffffffd358) at eval.c:2862
#99 0x00000000005eedfa in Ffuncall (nargs=3, args=0x7fffffffd350) at eval.c:2747
#100 0x0000000000630d52 in exec_byte_code (bytestr=10382812,
vector=10382845, maxdepth=62, args_template=3078, nargs=3,
args=0x7fffffffd9a8)
    at bytecode.c:880
#101 0x00000000005ef3b5 in funcall_lambda (fun=10382757, nargs=3,
arg_vector=0x7fffffffd990) at eval.c:2862
#102 0x00000000005eedfa in Ffuncall (nargs=4, args=0x7fffffffd988) at
eval.c:2747
#103 0x00000000005e7151 in Ffuncall_interactively (nargs=4,
args=0x7fffffffd988) at callint.c:252
#104 0x00000000005eea79 in Ffuncall (nargs=5, args=0x7fffffffd980) at
eval.c:2678
#105 0x00000000005edffe in Fapply (nargs=3, args=0x7fffffffda70) at eval.c:2326
#106 0x00000000005e75c9 in Fcall_interactively (function=673296,
record_flag=0, keys=13460885) at callint.c:389
#107 0x00000000005eebe6 in Ffuncall (nargs=4, args=0x7fffffffdcf8) at
eval.c:2705
#108 0x0000000000630d52 in exec_byte_code (bytestr=10383612,
vector=10383645, maxdepth=54, args_template=4102, nargs=1,
args=0x7fffffffe250)
    at bytecode.c:880
#109 0x00000000005ef3b5 in funcall_lambda (fun=10383565, nargs=1,
arg_vector=0x7fffffffe248) at eval.c:2862
#110 0x00000000005eedfa in Ffuncall (nargs=2, args=0x7fffffffe240) at
eval.c:2747
#111 0x00000000005ee5a1 in call1 (fn=14832, arg1=673296) at eval.c:2557
#112 0x000000000055482b in command_loop_1 () at keyboard.c:1484
#113 0x00000000005eba83 in internal_condition_case (bfun=0x554075
<command_loop_1>, handlers=19104, hfun=0x553862 <cmd_error>) at
eval.c:1314
#114 0x0000000000553d7f in command_loop_2 (ignore=0) at keyboard.c:1112
#115 0x00000000005eb3a3 in internal_catch (tag=45936, func=0x553d56
<command_loop_2>, arg=0) at eval.c:1079
#116 0x0000000000553d21 in command_loop () at keyboard.c:1091
#117 0x000000000055342a in recursive_edit_1 () at keyboard.c:697
#118 0x00000000005535be in Frecursive_edit () at keyboard.c:768
#119 0x0000000000551445 in main (argc=1, argv=0x7fffffffe6f8) at emacs.c:1626