I have previously saved list of breakpoints using
save breakpoints blist
now after compiling the program when I try to reload the same break points with the load command
load blist
I get this error
You can't do that when your target is `exec'
How to resolve this ?
load blist
Try source blist instead.
From "help save breakpoints":
Save current breakpoint definitions as a script.
The way to read a script is the source command. The load command means something different entirely.
I have breakpoints saved to file, say gdb.br, file content looks like:
br /project/src/file.c : 100
commands
silent
printf "\nbacktrace:\n"
bt
cont
end
This break just output backtrace and continue execution. You may also use simple breaks, like:
br /project/src/file.c : 100
br className::methodName
I have a lot of breaks there - gdb fails to add them via copy-past. Also I can't use load command on my multi-threading system.
To attach with gdb and load breakpoints I use this sequence:
gdb -p 1523 -x gdb.br
Where 1523 is process pid you want to attach to. -x is primarily
intedent to be used to load commands, set environment, but also could be used to load your breaks.
Hope this will help.
Related
I am trying to debug a very sporadic issue in my application. If ran ~1000 times my application surely hits a certain line it shouldn't and I would like to view the stack.
I tried using a gdb script cmd.gdb for this:
set logging overwrite on
set pagination off
set $n = 1000
break file.c:496
while $n-- > 0
ignore 1 9
condition 1 global_var == 10
run
end
How should I modify this script in order to print the stack when the breakpoint is reached?
I tried adding this after "run":
if $_siginfo
bt
loop_break
end
but it doesn't seem to work.
Actually, I have a Github repo with a Python-GDB extension, which does exactly the same thing as You have described, but with some more functionality.
You can just clone the repo:
git clone https://github.com/Viaceslavus/gdb-debug-until.git
and feed the python script to GDB with the following command inside GDB:
source <python script path>
Then, according to your example, you should run the next command:
debug-until file.c:496 --args="" --var-eq="global_var:10" -r=1000
*some remarks:
file.c:496 here is a starting breakpoint
"--args" parameter contains the arguments for your program
"--var-eq" is a debugging event, where 'global_var' is a variable name and '10' is a value
and finally the "-r" option specifies the number of times the program will be ran.
So all together this command will run your program 1000 times and will immediately notify You when the 'global_var' will be equal to 10.
Any additional information about the project could be found here:
https://github.com/Viaceslavus/gdb-debug-until.git in the README file.
GDB allows registering a set of commands to a specific breakpoint via commands NUM syntax. I need to register the set of commands for a specific breakpoint via an external file, by using a syntax something like the following:
commands ./main.c:18
silent
print buffer[0]
cont
end
commands ./io.c:29
silent
printf "Hello world %i\n", myvar1
cont
end
The commands path/to/file:XX syntax is made up by me. Because the NUM in commands NUM syntax requires exactly the breakpoint's runtime ID number (assigned by GDB), I can not use a deterministic syntax for that purpose.
I'm currently registering breakpoints via a text file with such a content:
break ./main.c:18
break ./io.c:29
and then issuing source breakpoints.txt command inside GDB. It seems that there is no way to register commands at the same time while registering a breakpoint:
(gdb) help break
Set breakpoint at specified line or function.
break [PROBE_MODIFIER] [LOCATION] [thread THREADNUM] [if CONDITION]
PROBE_MODIFIER shall be present if the command is to be placed in a
probe point. Accepted values are -probe' (for a generic, automatically guessed probe type), -probe-stap' (for a SystemTap probe) or
`-probe-dtrace' (for a DTrace probe).
LOCATION may be a line number, function name, or "*" and an address.
If a line number is specified, break at start of code for that line.
If a function is specified, break at start of code for that function.
If an address is specified, break at that exact address.
With no LOCATION, uses current execution address of the selected
stack frame. This is useful for breaking on return to a stack frame.
THREADNUM is the number from "info threads".
CONDITION is a boolean expression.
Multiple breakpoints at one place are permitted, and useful if their
conditions are different.
Question
Is there any easy way to set some predetermined commands for a predetermined breakpoint from within a file?
If not, is there any equivalent way to pass the (gdb) info breakpoints output to a file or a program while pipe is not available in GDB (version 5.3)? Currently I'm trying a workaround by using logging feature for that purpose:
set logging file /tmp/breakpoints
set logging on
info breakpoints
set logging off
Is there any easy way to set some predetermined commands for a predetermined breakpoint from within a file?
Yes: if you use commands without NUM, the commands will apply to the last breakpoint set. So you want something like:
break main.c:18
commands
silent
print buffer[0]
cont
end
I would like to script Trace32 so I can dump register state and pass to my script on a breakpoint trigger.
I am currently looking at the /CMD flag.
Is there any way I can set a breakpoint in the format of this:
Break.set main /CMD "OS.Command MyScript.sh $R0 $R1 $R2 ..."
where I am dumping the registers and passing it to MyScript as parameters.
My backup plan is to use wp.Register and have my script monitor file system instead.
Thanks ahead for help!
I have this solution.
When setting the breakpoint, instead use /CMD "DO bkpt_trigger.cmm"
Then in bkpt_trigger.cmm
&r0=Register(R0)
&r1=Register(R1)
...
Os.Command echo &r0 &r1
Let's say I'm debugging with valgrind and gdb by doing:
$ valgrind --vgdb-error=0 ./magic
...and then in a second terminal:
$ gdb ./magic
...
(gdb) target remote | /usr/lib/valgrind/../../bin/vgdb
If I want to examine the defined-ness of some memory, I can use:
(gdb) p &batman
$1 = (float *) 0xffeffe20c
(gdb) p sizeof(batman)
$2 = 4
(gdb) monitor get_vbits 0xffeffe20c 4
ffffffff
Using three commands to do one thing is kind of annoying, especially since I usually want to do this a few times for many different variables in the same stack frame. But if I try the obvious thing, I get:
(gdb) monitor get_vbits &batman sizeof(batman)
missing or malformed address
Is it possible to get gdb to evaluate &batman and sizeof(batman) on the same line as my monitor command?
But if I try the obvious thing, I get: missing or malformed address
This is from GDB doc (http://sourceware.org/gdb/onlinedocs/gdb/Connecting.html#index-monitor-1210) for the monitor cmd:
monitor cmd
This command allows you to send arbitrary commands
directly to the remote monitor. Since gdb doesn't care about the
commands it sends like this, this command is the way to extend gdb—you
can add new commands that only the external monitor will understand
and implement.
As you can see "gdb doesn't care about the commands it sends like this". It probably means that the command after monitor is not processed in any way and sent AS IS.
What you can do to evaluate your variable on the same line is to use user defined commands in gdb (http://sourceware.org/gdb/onlinedocs/gdb/Define.html). Define your own comand and use the eval gdb command to prepare your command with necessary values (http://sourceware.org/gdb/current/onlinedocs/gdb/Output.html#index-eval-1744):
define monitor_var
eval "monitor get_vbits %p %d", &$arg0, sizeof($arg0)
end
And then use it like this:
(gdb) monitor_var batman
I have read the following SO question:
Do specific action when certain breakpoint hits in gdb
Here, we use 'command' to decide what to do when the SPECIFIED Breakboint Gets Hit.
My Question is:
Suppose I put Breakpoints on ALL the Functions matching a given pattern:
gdb$rbreak func_
=> 100 Breakpoints (say)
When I execute this Code, I want to do the SAME Action - on hitting Each of these functions.
Hence, I cannot define something like:
command break_point_number
// since I don't know how many breakpoints will be there
Can somebody please suggest me:
How can I do a specific action-set when ANY Breakpoint gets Hit in GDB?
Thanks.
With a new enough version of gdb you can use a range:
(gdb) rbreak whatever
... gdb creates breakpoints N, N+1, ..., M
(gdb) commands N-M
> stuff
> end
I forget exactly when this feature went in.
With an older version of gdb, I'm not sure it can easily be done.
It can be done with difficulty: use set logging to write output to a file, then "info break", then "shell" to run scripts to edit the file into gdb commands, then "source". This is very painful.