When debugging C/C++ function that with many arguments, and each arguments may still call some functions, people have to repeated typing step and finish, then reach where this function's body part.
e.g. I'm using OpenCV's solvePnP() function, it requires many arguments:
solvePnP(v_point_3d,v_point_2d,K,D,R,T);
Among which, each argument will be converted from cv::Mat to cv::InputArray, thus calling a init() function.
What I expected is, directly go to where solvePnP() implemented, and I'm not interested in each argument type conversion.
Luckily, there is advance command in gdb. Official document is here， writes:
advance location
Continue running the program up to the given location. An argument is required, which should be of one of the forms described in Specify Location. Execution will also stop upon exit from the current stack frame. This command is similar to until, but advance will not skip over recursive function calls, and the target location doesn’t have to be in the same frame as the current one.
This gdb advance command really helps. And what's the equivalent command in LLDB?
I've search in lldb official's gdb => lldb command mapping web page, https://lldb.llvm.org/use/map.html , but not found.
Edit: I forgot to mention, the gdb usage for me is
(gdb) b main
(gdb) r
(gdb) advance solvePnP
Checkout the sif command for lldb. sif means **Step Into Function
Reference: How to step-into outermost function call in the line with LLDB?
To get all the supported commands of LLDB, one should first go into lldb command, then type help, then there will be the explanations for sif:
sif -- Step through the current block, stopping if you step directly into a function whose name matches the TargetFunctionName.
Related
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 step into the function GDB is currently at, but not into the functions that are called to prepare the parameters for the call.
Is there a single command in gdb that steps over functions like initial_metadata_flags() and directly into SendInitialMetadata?
void StartCallInternal() {
> single_buf.SendInitialMetadata(&context_->send_initial_metadata_,
context_->initial_metadata_flags());
}
If there is, I did not see it mentioned here: https://sourceware.org/gdb/onlinedocs/gdb/Continuing-and-Stepping.html
My current workaround is to step, finish, step, finish, until I get to the primary function on that line. But would like something more direct.
There are similar questions asked about Python and Visual Studio, but I haven't found a good answer for gdb.
You can configure functions that you want to skip while stepping:
(gdb) help skip
Ignore a function while stepping.
Usage: skip [FUNCTION-NAME]
skip [FILE-SPEC] [FUNCTION-SPEC]
If no arguments are given, ignore the current function.
FILE-SPEC is one of:
-fi|-file FILE-NAME
-gfi|-gfile GLOB-FILE-PATTERN
FUNCTION-SPEC is one of:
-fu|-function FUNCTION-NAME
-rfu|-rfunction FUNCTION-NAME-REGULAR-EXPRESSION
...
I'm debugging an app with GDB and when I step into a frame, I see something like this:
#2 0x00007fff4da4276b in MHWRender::THgeometryOverrideEvaluator::doDGBoundingBox(TdgContext const&, OGSMayaCompoundNode*) ()
Normally, I'd just print out parameter addresses, but in the case of the second parameter here, there's no parameter name. How do I get the info I need?
How do I get the info I need?
The output you got is indicative of the code being compiled without debug info.
The easiest fix is to add -g as appropriate and rebuild your application.
Without debug info, you can only do debugging at assembly level, which requires knowing the calling convention on your platform (which you did not specify).
Assuming this is Linux on x86_64, and assuming that doDGBoundingBox is not a static function, the first (this) parameter will be passed in $rdi, second (the TdgContext&) in $rsi, and third (the OGSMayaCompoundNode*) in $rdx. Reference.
I've set a breakpoint in gdb, and I'd like to see the exact line of source the breakpoint is on, just to confirm it's correct -- is there a quick way to do this?
The "info b" command gives me information about the breakpoints, but it doesn't display source:
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00000000006c3ba4 in MyClass::foo(bar*)
at /home/user1/src/MyClass.cpp:1021
I can type "list MyClass.cpp:1021" to see the lines around this breakpoint, but I'm wondering if there's a shorter way. Googling and reading the gdb manual didn't turn up anything.
I know that if I'm executing the program and have hit the breakpoint, I can just type "list", but I'm asking specifically about the case where I am not at the breakpoint (the program may not even be running).
You can use the list command to show sources. list takes a "linespec", which is gdb terminology for the kinds of arguments accepted by break. So, you can either pass it whatever argument you used to make the breakpoint in the first place (e.g., list function) or you can pass it the file and line shown by info b (e.g., list mysource.c:75).
I think the closest one can get to this is by turning the history on (set history save on) and then press CTRL-R to do a reverse search for the former list command.
More specifically, change your workflow when setting a breakpoint. After each command like b main GDB shows the source file like path/to/main.cpp, line 12. Immediately use this information in a quick list main.cpp:12. To show this location later press CTRL-R and type "main".
https://sourceware.org/gdb/onlinedocs/gdb/Command-History.html
I have read the following SO question:
Do specific action when certain breakpoint hits in gdb
Here, we use 'command' to decide what to do when the SPECIFIED Breakboint Gets Hit.
My Question is:
Suppose I put Breakpoints on ALL the Functions matching a given pattern:
gdb$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.