gdb bt gives only ??, how can I debug?
/var/log/message:
segfault at 0 ip 00007fcd16e5853a sp 00007ffd98e37e58 error 4 in libc-2.24.so[7fcd16dc9000+195000]
addr2line -e a.out 00007fcd16e5853a
??:0
gdb bt
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007fcd16e5853a in ?? ()
(gdb) bt
#0 0x00007fcd16e5853a in ?? ()
#1 0x000055f2f45fe95b in ?? ()
#2 0x000055f200000080 in ?? ()
#3 0x00007fcd068c2040 in ?? ()
#4 0x000055f2f6109c48 in ?? ()
#5 0x0000000000000000 in ?? ()
build with gcc -Wall -O0 -g
How can I debug this, are there more methods?
c debugging gcc segmentation-fault gdb
asked Nov 24 '18 at 13:30
gacopugacopu
1459
add a comment |
/var/log/message:
segfault at 0 ip 00007fcd16e5853a sp 00007ffd98e37e58 error 4 in libc-2.24.so[7fcd16dc9000+195000]
addr2line -e a.out 00007fcd16e5853a
??:0
gdb bt
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007fcd16e5853a in ?? ()
(gdb) bt
#0 0x00007fcd16e5853a in ?? ()
#1 0x000055f2f45fe95b in ?? ()
#2 0x000055f200000080 in ?? ()
#3 0x00007fcd068c2040 in ?? ()
#4 0x000055f2f6109c48 in ?? ()
#5 0x0000000000000000 in ?? ()
build with gcc -Wall -O0 -g
How can I debug this, are there more methods?
c debugging gcc segmentation-fault gdb
asked Nov 24 '18 at 13:30
gacopugacopu
1459
Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
1
Do you link with-g? Doesgdbsay that debuginfo has been loaded?
– Maxim Egorushkin
Nov 24 '18 at 14:04
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26
add a comment |
/var/log/message:
segfault at 0 ip 00007fcd16e5853a sp 00007ffd98e37e58 error 4 in libc-2.24.so[7fcd16dc9000+195000]
addr2line -e a.out 00007fcd16e5853a
??:0
gdb bt
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007fcd16e5853a in ?? ()
(gdb) bt
#0 0x00007fcd16e5853a in ?? ()
#1 0x000055f2f45fe95b in ?? ()
#2 0x000055f200000080 in ?? ()
#3 0x00007fcd068c2040 in ?? ()
#4 0x000055f2f6109c48 in ?? ()
#5 0x0000000000000000 in ?? ()
build with gcc -Wall -O0 -g
How can I debug this, are there more methods?
c debugging gcc segmentation-fault gdb
asked Nov 24 '18 at 13:30
gacopugacopu
1459
/var/log/message:
segfault at 0 ip 00007fcd16e5853a sp 00007ffd98e37e58 error 4 in libc-2.24.so[7fcd16dc9000+195000]
addr2line -e a.out 00007fcd16e5853a
??:0
gdb bt
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007fcd16e5853a in ?? ()
(gdb) bt
#0 0x00007fcd16e5853a in ?? ()
#1 0x000055f2f45fe95b in ?? ()
#2 0x000055f200000080 in ?? ()
#3 0x00007fcd068c2040 in ?? ()
#4 0x000055f2f6109c48 in ?? ()
#5 0x0000000000000000 in ?? ()
build with gcc -Wall -O0 -g
How can I debug this, are there more methods?
c debugging gcc segmentation-fault gdb
c debugging gcc segmentation-fault gdb
asked Nov 24 '18 at 13:30
gacopugacopu
1459
asked Nov 24 '18 at 13:30
gacopugacopu
1459
asked Nov 24 '18 at 13:30
gacopugacopu
1459
asked Nov 24 '18 at 13:30
gacopugacopu
1459
asked Nov 24 '18 at 13:30
gacopugacopu
1459
1459
Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
1
Do you link with-g? Doesgdbsay that debuginfo has been loaded?
– Maxim Egorushkin
Nov 24 '18 at 14:04
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26
add a comment |
Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
1
Do you link with-g? Doesgdbsay that debuginfo has been loaded?
– Maxim Egorushkin
Nov 24 '18 at 14:04
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26
Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
1
1
Do you link with
-g? Does gdb say that debuginfo has been loaded?– Maxim Egorushkin
Nov 24 '18 at 14:04
Do you link with
-g? Does gdb say that debuginfo has been loaded?– Maxim Egorushkin
Nov 24 '18 at 14:04
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26
add a comment |
1 Answer
1
active
oldest
votes
gdb bt
Surely that is not the command you actually executed.
Most likely you did something like this:
gdb /path/to/core
(gdb) bt
Don't do that. Do this instead:
gdb /path/to/a.out /path/to/core
(gdb) bt
If you already did invoke GDB correctly, other likely reasons why bt did not work:
- You are analyzing the
coreon a different machine from the one on which it was produced. See this answer. - You rebuilt
a.outwith different flags. Use the exact binary that crashed. - You have updated
libcafter the core was produced. Restore it to the version that was current as of when the core was produced.
P.S. This command
addr2line -e a.out 00007fcd16e5853a
makes no sense: the error message told you that the address 00007fcd16e5853a is in libc-2.24.so. The a.out has nothing to do with that address.
The command you want to use is:
addr2line -fe /path/to/libc-2.24.so 195000
P.P.S.
segfault at 0 ip 00007fcd16e5853a ...
This means: NULL pointer dereference inside libc. The most probable cause: not checking for error return, e.g. something like:
FILE *fp = fopen("/some/file", "r");
fscanf(fp, buffer, sizeof(buffer)); // Oops: didn't check for NULL.
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
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active
oldest
votes
gdb bt
Surely that is not the command you actually executed.
Most likely you did something like this:
gdb /path/to/core
(gdb) bt
Don't do that. Do this instead:
gdb /path/to/a.out /path/to/core
(gdb) bt
If you already did invoke GDB correctly, other likely reasons why bt did not work:
- You are analyzing the
coreon a different machine from the one on which it was produced. See this answer. - You rebuilt
a.outwith different flags. Use the exact binary that crashed. - You have updated
libcafter the core was produced. Restore it to the version that was current as of when the core was produced.
P.S. This command
addr2line -e a.out 00007fcd16e5853a
makes no sense: the error message told you that the address 00007fcd16e5853a is in libc-2.24.so. The a.out has nothing to do with that address.
The command you want to use is:
addr2line -fe /path/to/libc-2.24.so 195000
P.P.S.
segfault at 0 ip 00007fcd16e5853a ...
This means: NULL pointer dereference inside libc. The most probable cause: not checking for error return, e.g. something like:
FILE *fp = fopen("/some/file", "r");
fscanf(fp, buffer, sizeof(buffer)); // Oops: didn't check for NULL.
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
add a comment |
gdb bt
Surely that is not the command you actually executed.
Most likely you did something like this:
gdb /path/to/core
(gdb) bt
Don't do that. Do this instead:
gdb /path/to/a.out /path/to/core
(gdb) bt
If you already did invoke GDB correctly, other likely reasons why bt did not work:
- You are analyzing the
coreon a different machine from the one on which it was produced. See this answer. - You rebuilt
a.outwith different flags. Use the exact binary that crashed. - You have updated
libcafter the core was produced. Restore it to the version that was current as of when the core was produced.
P.S. This command
addr2line -e a.out 00007fcd16e5853a
makes no sense: the error message told you that the address 00007fcd16e5853a is in libc-2.24.so. The a.out has nothing to do with that address.
The command you want to use is:
addr2line -fe /path/to/libc-2.24.so 195000
P.P.S.
segfault at 0 ip 00007fcd16e5853a ...
This means: NULL pointer dereference inside libc. The most probable cause: not checking for error return, e.g. something like:
FILE *fp = fopen("/some/file", "r");
fscanf(fp, buffer, sizeof(buffer)); // Oops: didn't check for NULL.
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
add a comment |
gdb bt
Surely that is not the command you actually executed.
Most likely you did something like this:
gdb /path/to/core
(gdb) bt
Don't do that. Do this instead:
gdb /path/to/a.out /path/to/core
(gdb) bt
If you already did invoke GDB correctly, other likely reasons why bt did not work:
- You are analyzing the
coreon a different machine from the one on which it was produced. See this answer. - You rebuilt
a.outwith different flags. Use the exact binary that crashed. - You have updated
libcafter the core was produced. Restore it to the version that was current as of when the core was produced.
P.S. This command
addr2line -e a.out 00007fcd16e5853a
makes no sense: the error message told you that the address 00007fcd16e5853a is in libc-2.24.so. The a.out has nothing to do with that address.
The command you want to use is:
addr2line -fe /path/to/libc-2.24.so 195000
P.P.S.
segfault at 0 ip 00007fcd16e5853a ...
This means: NULL pointer dereference inside libc. The most probable cause: not checking for error return, e.g. something like:
FILE *fp = fopen("/some/file", "r");
fscanf(fp, buffer, sizeof(buffer)); // Oops: didn't check for NULL.
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
gdb bt
Surely that is not the command you actually executed.
Most likely you did something like this:
gdb /path/to/core
(gdb) bt
Don't do that. Do this instead:
gdb /path/to/a.out /path/to/core
(gdb) bt
If you already did invoke GDB correctly, other likely reasons why bt did not work:
- You are analyzing the
coreon a different machine from the one on which it was produced. See this answer. - You rebuilt
a.outwith different flags. Use the exact binary that crashed. - You have updated
libcafter the core was produced. Restore it to the version that was current as of when the core was produced.
P.S. This command
addr2line -e a.out 00007fcd16e5853a
makes no sense: the error message told you that the address 00007fcd16e5853a is in libc-2.24.so. The a.out has nothing to do with that address.
The command you want to use is:
addr2line -fe /path/to/libc-2.24.so 195000
P.P.S.
segfault at 0 ip 00007fcd16e5853a ...
This means: NULL pointer dereference inside libc. The most probable cause: not checking for error return, e.g. something like:
FILE *fp = fopen("/some/file", "r");
fscanf(fp, buffer, sizeof(buffer)); // Oops: didn't check for NULL.
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
edited Nov 25 '18 at 3:52
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
answered Nov 24 '18 at 16:31
Employed RussianEmployed Russian
125k20168238
125k20168238
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
add a comment |
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
Thanks, the gdb part is correct, I just simplified that. I'll check the libc part NULL check
– gacopu
Nov 25 '18 at 2:28
add a comment |
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Corrupted stack? Use e.g. Valgrind or similar to help you find the problem?
– Some programmer dude
Nov 24 '18 at 13:34
1
Do you link with
-g? Doesgdbsay that debuginfo has been loaded?– Maxim Egorushkin
Nov 24 '18 at 14:04
Oh and you don't strip the debug info once you've built the program?
– Some programmer dude
Nov 24 '18 at 14:05
@Someprogrammerdude no, I didn't strip, and don't know why, if I run it use valgrind, it's too slow, so the bug just does not appear.
– gacopu
Nov 25 '18 at 2:26
@MaximEgorushkin yes, linked with -g and debuginfo installed
– gacopu
Nov 25 '18 at 2:26