GDB is a wonderful tool if you are using linux as your platform for software development.
I will list done some of the frequently used approaches here.
I will list done some of the frequently used approaches here.
watch point:
awatch *0x8092581000
rwatch *0x8092581000
it will start breaking whenever there is read/write at: 0xa87c0e255f7f0080
find /g 0x8080000000,0x8092581000, 0x8080459578
-- this is to search for value: 0x8080459578 between address 0x8080000000 && 0x8092581000
find 0x8080000000,0x8092581000, "tbl_sm_main"
-- this is to search a string.
find /g 0x8080000000,0x8092581000, 0x8080459578
-- this is to search for value: 0x8080459578 between address 0x8080000000 && 0x8092581000
find 0x8080000000,0x8092581000, "tbl_sm_main"
-- this is to search a string.
Printf usage
printf "Delete object: %d\n", i
Commands:
1. info frame
-- will list down the registry level info about the particular frame, it will be useful when you are debugging cores.
2. info args
-- will list the arguments passed to the function in particular frame.
3. disassemble
-- will give the assembly code for the function.
4. disassemble 0xf1704f0 0xf17050f
-- will give the assembly code between two addresses
5. info registers
-- will give the details of registers and stored values
6. info reg OR x $
-- will output the contents for regiser, ex1: info reg r32 ex2: x $r32
7. info source
8. info sources
9. set pagination on/off
10. x/32w 0x100f3000
-- To print 32 words from address 0x100f3000
11. x/s
-- To print contents of the address as string
12. x/nc -- To print content of the address as character, it will print "n" characters starting from the address.
13. x/t -- To print in binary
14. x/nx -- To print in hexa
15. core
-- To attached to the core file
16. generate-core-file
-- To generate a core at the particular instance on a running process.
17. set follow-fork-mode parent/child/ask
-- To set whether to follow parent or child or ask whom to follow.
18. show follow-fork-mode
-- To display the status of fork mode
19. set history expansion on -- To enable capturing history, you can "!" to rerun the olde commands as similar to Bash command. 20. set height
To allow the system to dump the core:
default configuration file for gdb is: .gdbinit
To print the size of the structure in GDB:
p sizeof(struct ) ---- make sure symbol for the structure is present.
Breakpoints:
#include
void assert(int expression);
If expression evaluates to 0 (false), then the expression, sourcecode filename, and line number are sent to the standard error, and then calls the abort function.
To enable core dumps for your current shell, use ulimit to set a maximal core dump size in megabytes.
For this example, we'll "limit" core dumps to 1 gigabyte:
$ulimit -c 1024
To use macros in the gdb use following option during compiling:
#define NDEBUG === > then the macro assert does nothing.
References:
http://sourceware.org/gdb/onlinedocs/gdb/Forks.html
http://arioch.unomaha.edu/~jclark/gdb_plus.html
http://discussknowhow.blogspot.com/2008/07/analyzing-core-dumps-and-assert.html
http://developer.apple.com/mac/library/documentation/DeveloperTools/gdb/gdb/gdb_10.html
http://www.haifux.org/lectures/222/GDB_haifux_David_Khosid.pdf -- Advanced debbuging with gdb
GNU Debugger - Advanced GDB Actions - GoldhiveWiki http://sunsite.ualberta.ca/Documentation/Gnu/gdb-4.18/html_chapter/gdb_15.html http://web.mit.edu/gnu/doc/html/gdb_10.html https://eli.thegreenplace.net/2011/09/06/stack-frame-layout-on-x86-64
Commands:
1. info frame
-- will list down the registry level info about the particular frame, it will be useful when you are debugging cores.
2. info args
-- will list the arguments passed to the function in particular frame.
3. disassemble
-- will give the assembly code for the function.
4. disassemble 0xf1704f0 0xf17050f
-- will give the assembly code between two addresses
5. info registers
-- will give the details of registers and stored values
6. info reg
-- will output the contents for regiser, ex1: info reg r32 ex2: x $r32
7. info source
8. info sources
9. set pagination on/off
10. x/32w 0x100f3000
-- To print 32 words from address 0x100f3000
11. x/s
-- To print contents of the address as string
12. x/nc -- To print content of the address as character, it will print "n" characters starting from the address.
13. x/t -- To print in binary
14. x/nx -- To print in hexa
15. core
-- To attached to the core file
16. generate-core-file
-- To generate a core at the particular instance on a running process.
17. set follow-fork-mode parent/child/ask
-- To set whether to follow parent or child or ask whom to follow.
18. show follow-fork-mode
-- To display the status of fork mode
19. set history expansion on -- To enable capturing history, you can "!" to rerun the olde commands as similar to Bash command. 20. set height
To allow the system to dump the core:
ulimit -c unlimited
History related commands:- These commands display the state of the GDB history parameters.
show historyshow history filenameshow history saveshow history sizeshow history expansionshow commands- Display the last ten commands in the command history.
show commands n- Print ten commands centered on command number n.
show commands +- Print ten commands just after the commands last printed.
Logging related commands:
show logging # displays weather logging is on / off
set logging on # enable logging
set logging off # disable logging
set logging file log-file.txt # set name for log file, default is gdb.txtset logging overwrite # To append logs of debug sessions or create new on every debug session using
Good post on checkpoints:
http://sourceware.org/gdb/onlinedocs/gdb/Checkpoint_002fRestart.html#Checkpoint_002fRestart
Tracing function calls of process through gdb:
http://stackoverflow.com/questions/311840/tool-to-trace-local-function-calls-in-linux#312058
Breaking the process whenever a function from a specific file is getting executed:
http://stackoverflow.com/questions/475283/using-gdb-stop-the-program-when-it-is-using-any-function-from-file-x
default configuration file for gdb is: .gdbinit
To print the size of the structure in GDB:
p sizeof(struct
Breakpoints:
- break FUNCTION
- Set a breakpoint at entry to function FUNCTION.
- break LINENUM
- Set a breakpoint at line LINENUM in the current source file.
- break FILENAME:LINENUM
- Set a breakpoint at line LINENUM in source file FILENAME.
- break FILENAME:FUNCTION
- Set a breakpoint at entry to function FUNCTION found in file FILENAME.
- break ... if COND
- Set a breakpoint with condition COND; evaluate the expression COND each time the breakpoint is reached, and stop only if the value is nonzero--that is, if COND evaluates as true. ... stands for one of the possible arguments described above (or no argument) specifying where to break.
#include
void assert(int expression);
If expression evaluates to 0 (false), then the expression, sourcecode filename, and line number are sent to the standard error, and then calls the abort function.
To enable core dumps for your current shell, use ulimit to set a maximal core dump size in megabytes.
For this example, we'll "limit" core dumps to 1 gigabyte:
$ulimit -c 1024
To use macros in the gdb use following option during compiling:
gcc -gdwarf-2 -g3 sample.c -o sample
#define NDEBUG === > then the macro assert does nothing.
References:
http://sourceware.org/gdb/onlinedocs/gdb/Forks.html
http://arioch.unomaha.edu/~jclark/gdb_plus.html
http://discussknowhow.blogspot.com/2008/07/analyzing-core-dumps-and-assert.html
http://developer.apple.com/mac/library/documentation/DeveloperTools/gdb/gdb/gdb_10.html
http://www.haifux.org/lectures/222/GDB_haifux_David_Khosid.pdf -- Advanced debbuging with gdb
GNU Debugger - Advanced GDB Actions - GoldhiveWiki http://sunsite.ualberta.ca/Documentation/Gnu/gdb-4.18/html_chapter/gdb_15.html http://web.mit.edu/gnu/doc/html/gdb_10.html https://eli.thegreenplace.net/2011/09/06/stack-frame-layout-on-x86-64
