Development/GDB - Revision history

S Richling: /* Branch record tracing */

2022-12-08T22:49:49Z

Branch record tracing

← Older revision		Revision as of 00:49, 9 December 2022
Line 82:		Line 82:
	This allows disassembling previously executed instructions, checking for previously called functions and branch tracing.		This allows disassembling previously executed instructions, checking for previously called functions and branch tracing.

	Honestly, Segmentation Violations are better caught using [[Valgrind]]. However in this case,		Honestly, Segmentation Violations are better caught using [[Development/Valgrind\|Valgrind]]. However in this case,
	<kbd>valgrind</kbd> would ''not'' have helped: this loops overwrites <kbd>v</kbd> an		<kbd>valgrind</kbd> would ''not'' have helped: this loops overwrites <kbd>v</kbd> an
	array of 2 ints on the stack and the return address leading to the execution of IP <kbd>0x07</kbd>.		array of 2 ints on the stack and the return address leading to the execution of IP <kbd>0x07</kbd>.

S Richling at 22:39, 8 December 2022

2022-12-08T22:39:25Z

← Older revision		Revision as of 00:39, 9 December 2022
Line 102:		Line 102:
	GDB can also be useful for multithreaded applications for example when OpenMP was used. By going through each thread separately you can better see what is really going on and you can check the computation step by step.		GDB can also be useful for multithreaded applications for example when OpenMP was used. By going through each thread separately you can better see what is really going on and you can check the computation step by step.
	The following commands are useful for multithreaded debugging:		The following commands are useful for multithreaded debugging:


	[[Category:debugger software]][[Category:bwUniCluster]]

S Richling: S Richling moved page GDB to Development/GDB: Umzug in den Development-Bereich

2022-12-07T11:28:00Z

S Richling moved page GDB to Development/GDB: Umzug in den Development-Bereich

← Older revision	Revision as of 13:28, 7 December 2022
(No difference)

H Winkhardt at 13:18, 21 December 2021

2021-12-21T13:18:00Z

← Older revision		Revision as of 15:18, 21 December 2021
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	{{Softwarepage}}		{{Softwarepage\|devel/gdb}}

	{\| width=600px class="wikitable"		{\| width=600px class="wikitable"

H Winkhardt at 14:57, 15 December 2021

2021-12-15T14:57:44Z

Show changes

H Winkhardt at 14:54, 15 December 2021

2021-12-15T14:54:53Z

@@ Line 1: / Line 1: @@
 {| width=600px class="wikitable"
 |-
@@ Line 5: / Line 7: @@
 | module load
 | devel/gdb
 |-
 | License
@@ Line 25: / Line 24: @@
 |}
 <br>
-= Introduction =
+= Description =
 The '''GNU Debugger (GDB)''' is a standard debugger for serial programs although it can be used for parallel and even distributed programs with few processes too. In the past Intel supported their own '''idb''' debugger, however this has been deprecated in favor of their own port called <kbd>gdb-ia</kbd>.
 <br>
 = Basic commands =
@@ Line 134: / Line 78: @@
 '''Example:'''
 We debug the following program called <kbd>bug.c</kbd> which crashes on execution.
 <source lang="c">
 #include <stdio.h>
@@ Line 166: / Line 111: @@
 </source>
-'''Sample GDB session:'''
+'''Example GDB session:'''
 <pre>
 $ gcc -Wall -O0 -g bug.c -o bug

R Keller: /* Branch record tracing */

2020-10-29T14:23:28Z

Branch record tracing

← Older revision		Revision as of 16:23, 29 October 2020
Line 295:		Line 295:
	</pre>		</pre>

	Honestly, ~~above~~ Segmentation ~~Violation~~ ~~would~~ ~~have been~~ caught ~~much~~ ~~easier~~ by ~~using~~ ~~<kbd>valgrind</kbd>.~~		Honestly, Segmentation Violations are better caught using [[Valgrind]]. However in this case,
			<kbd>valgrind</kbd> would ''not'' have helped: this loops overwrites <kbd>v</kbd> an
			array of 2 ints on the stack and the return address leading to the execution of IP <kbd>0x07</kbd>.

	More information is available in [https://sourceware.org/gdb/current/onlinedocs/gdb/Process-Record-and-Replay.html#Process-Record-and-Replay gdb's feature documentation]		More information is available in [https://sourceware.org/gdb/current/onlinedocs/gdb/Process-Record-and-Replay.html#Process-Record-and-Replay gdb's feature documentation]

R Keller: /* Branch record tracing */

2020-10-29T14:18:33Z

Branch record tracing

R Keller: /* Branch record tracing */

2020-10-29T14:15:08Z

Branch record tracing

← Older revision		Revision as of 16:15, 29 October 2020
Line 260:		Line 260:
	3 main		3 main
	4 loop		4 loop
			(gdb) # Even more detail with the instruction counts and line numbers included:
			(gdb) record function-call-history /ilc
			1 main inst 1,2 at bug.c:24
			2 begin inst 3,8 at bug.c:5,7
			3 main inst 9,10 at bug.c:25
			4 loop inst 11,131 at bug.c:9,17
	(gdb) # Disassembles the last 10 instructions executed leading to the crash.		(gdb) # Disassembles the last 10 instructions executed leading to the crash.
	(gdb) record instruction-history		(gdb) record instruction-history

R Keller: /* Branch record tracing */

2020-10-29T14:13:05Z

Branch record tracing

@@ Line 254: / Line 254: @@
 Buffer size: 16kB.
 Recorded 131 instructions in 4 functions (0 gaps) for thread 1 (process 1153077).
-(gdb) # Show the last 10 instructions executed leading to the crash.
+(gdb) # The last function call history shows the control flow on function level
 (gdb) record instruction-history
 0x0000000000400565 <loop+30>:        mov    -0x8(%rbp),%eax
@@ Line 266: / Line 272: @@
 0x000000000040057c <loop+53>:        pop    %rbp
 0x000000000040057d <loop+54>:        ret
-(gdb) # The last function call history shows the control flow:
+(gdb) # And another 10 disassembled instructions, nicely showing the control flow
-(gdb) record function-call-history
+(gdb) record instruction-history -
 </pre>
 More information is available in [https://sourceware.org/gdb/current/onlinedocs/gdb/Process-Record-and-Replay.html#Process-Record-and-Replay gdb's feature documentation]

← Older revision		Revision as of 16:18, 29 October 2020
Line 266:		Line 266:
	3 main inst 9,10 at bug.c:25		3 main inst 9,10 at bug.c:25
	4 loop inst 11,131 at bug.c:9,17		4 loop inst 11,131 at bug.c:9,17
	(gdb) # Disassembles the last 10 instructions executed leading to the crash.		(gdb) # Disassembles the last 10 instructions (mixed with source code) executed leading to the crash.
	(gdb) record instruction-history		(gdb) record instruction-history /m
			bug.c:15 v[k] = i;
	122 0x0000000000400565 <loop+30>: mov -0x8(%rbp),%eax		122 0x0000000000400565 <loop+30>: mov -0x8(%rbp),%eax
	123 0x0000000000400568 <loop+33>: cltq		123 0x0000000000400568 <loop+33>: cltq
	124 0x000000000040056a <loop+35>: mov -0x4(%rbp),%edx		124 0x000000000040056a <loop+35>: mov -0x4(%rbp),%edx
	125 0x000000000040056d <loop+38>: mov %edx,-0x10(%rbp,%rax,4)		125 0x000000000040056d <loop+38>: mov %edx,-0x10(%rbp,%rax,4)
			bug.c:13 for(i = 0; i < 8; i++) {
	126 0x0000000000400571 <loop+42>: addl $0x1,-0x4(%rbp)		126 0x0000000000400571 <loop+42>: addl $0x1,-0x4(%rbp)
	127 0x0000000000400575 <loop+46>: cmpl $0x7,-0x4(%rbp)		127 0x0000000000400575 <loop+46>: cmpl $0x7,-0x4(%rbp)
	128 0x0000000000400579 <loop+50>: jle 0x400554 <loop+13>		128 0x0000000000400579 <loop+50>: jle 0x400554 <loop+13>
			bug.c:17 }
	129 0x000000000040057b <loop+52>: nop		129 0x000000000040057b <loop+52>: nop
	130 0x000000000040057c <loop+53>: pop %rbp		130 0x000000000040057c <loop+53>: pop %rbp
	131 0x000000000040057d <loop+54>: ret		131 0x000000000040057d <loop+54>: ret
	(gdb) # And another 10 disassembled instructions, nicely showing the control flow		(gdb) # And another 10 disassembled instructions, nicely showing the control flow
	(gdb) record instruction-history -		(gdb) record instruction-history -