I'm trying to get gdb to run programs with input redirection to stdin. For example, without gdb I would run a program like this:
prog < input.txt
Now in gdb, the usual way to do this is run < input.txt. However, it doesn't work for me and when doing this nothing gets redirected into stdin.
I'm using Windows with MinGW. What could be the problem?
As far back as the late '90s, broken command line redirection was a known and assumed limitation. My suspicion is that it remains that way, since the mingw32 port of gdb still gleefully passes on verbatim all run arguments (including redirects) to the debugee.
Several possible workarounds:
if you have the option to alter the command line interface, then implement bbadour's suggestion
otherwise, if you can easily suspend the process before the point you want to debug at, invoke the debugee (with redirection) from a shell and attach to it while it is already running
otherwise, if you have symbols for the debugee (gcc -g) or you know the address of main() (gcc -Wl,-Map,mapfile) and can set a breakpoint there, proceed in the following manner (tested with mingw gdb 6.8.0):
# gdb debugee.exe
(gdb) b main
(gdb) run non-redirect-arguments-if-any
(gdb) p dup2(open("/tmp/input.txt", 0), 0)
(gdb) c
I ran into the same issue here, and I just got into the habit of adding a command-line argument to allow grabbing input from a file.
e.g. Parsing a "-i ifile" argument using argc and argv to get input from ifile instead of stdin and parsing a "-o ofile" to write output to ofile instead of stdout.
Then I just use those arguments instead of redirects.
The tools that come with MinGW often are not the latest versions and often have features omitted. ::shrug::
Input redirection is supported starting with GDB 8.0. From the NEWS file:
Native debugging on MS-Windows supports command-line redirection
Command-line arguments used for starting programs on MS-Windows
can now include redirection symbols supported by native Windows
shells, such as '<', '>', '>>', '2>&1', etc. This affects GDB
commands such as "run", "start", and "set args", as well as the
corresponding MI features.
Related
I'm not very into unix/linux, I'm using rhat linux with sh, tcsh shells.
What I'm trying to do is to debug lifecycle of the object of the class by breaking on it's default, copy c-tors, on d-tor and on operator=; move operations are not defined neither by compiler or me. I break on these functions and printf some lines and also print backtrace
br /project/src/some_file.c:408
commands
silent
printf "<%p> D E F A U L T c-tor bt:\n", this
bt
cont
end
The thing is there're a lot objects of this class, so there is a lot of output, and nothing helps me to disable output to the terminal, so I want see gdb output only in the file, not in the shell. Is it possible to achieve using sh or tcsh? - I can't really impact on the environment and use some other debugger or shell. The reason I want to disable any output from gdb and process being debugged to the shell is because I believe it slows down gdb and execution of the debugged process, which breaks behavior of debugged application.
Using gdb 8.1. I tried logging options of gdb, redirecting output by
run > somefile
and I tried to run gdb like this
gdb -p 1000 -x breakpoint.txt | tee somefile.txt
Thanks many times!
this link has various option for logging
http://sourceware.org/gdb/onlinedocs/gdb/Logging-Output.html
simple one is
set logging file file
Change the name of the current logfile. The default logfile is gdb.txt.
then
set logging on
Enable logging.
I recently decided to start teaching myself C++ and thought a simple encryption project would be a good place to start, since it covers most of the basics (cout, cin, opening files, etc). Is there a way to have the code open a terminal window similar to the one opened when I compile and run from sublime text?
I have tried this so far, but it hasn't changed anything.
string cmd = "gnome-terminal-x sh-c 'ls-l; exec bash'";
system(cmd.c_str());
Essentially, I would like to be able to run the program by clicking the .exe, and have the terminal where all of the input and output goes pop up.
You don't need to write any code, you just need to configure the shortcut to launch the program in a terminal. Here's a Gnome dialog that shows that option:
Problem seems to be gnome-terminal, or then just my failure to give it the right arguments. For example gnome-terminal -x sh -c 'ls -l ; exec bash' from command line in another terminal just opens an empty gnome-terminal and spits out a bunch of glib warnings to original terminal... (Note to readers: if you can give the right command that works for gnome-terminal, please let me know in comments or just edit this paragraph.)
However, using xterm works, for example xterm -e sh -c 'ls -l; exec bash', or a line for your code:
string cmd = "xterm -e sh -c 'ls -l; exec bash'";
As a side note, the command to open the default x terminal window of the DE is x-terminal-emulator, but it quite often has the practical problem of different terminals taking different arguments, so sadly you're probably better of using a specific terminal, like that xterm, and requiring that to be installed, or letting user to configure what terminal to use, with what arguments (though letting user to specify any command to be run can also be a security risk, if user is not always trusted).
Just be very careful with escaping. For example, when you test the command form command line, and then copy-paste it to C++ string literal, you need to escape every " and \ one more time for C++. If you have trouble with this, check out C++11 raw strings.
Escaping becomes extra important if you construct the command string at runtime, and especially if you accept user input and add that to the string. In that case, better search for and use some existing library like GLib, or sanitize the user input very carefully (ie. just paranoidically reject anything with chars, which may have a special meaning in shell in some context).
If you are actually asking, how can my program open a console window for itself similar to how Windows console programs behave, and redirect it's own stdin, stdout and stderr there, as if it was launched from command line, that that is not very easy from the same binary, and it is not commonly done like that in Unix.
If you want a behaviour like that, you could create a desktop shortcut, but more general way is to write a wrapper shell script, which starts your binary in a terminal. What kind of script exactly, depends on how you want it to behave exactly: what will it do with stdio, will it return or wait for program to exit, how do you want it to find the binary, how does it behave when run from command line instead of double-clicking from GUI, etc.
Background info: The C++ program(LAMMPS - an open source) takes in a input script that has all the commands to be executed. The executable is named "lmp_fedora", input script named "in.hit". The program's run command "./lmp_fedora < in.hit"
My Problem: I am trying to debug one of the .cpp files in LAMMPS.
My Attempts: 1. I tried "gdb lmp_fedora < in.hit", but it failed. 2. Also tried to find the pid of the running program using ps aux, but wasn't sure which id it was.
My Question: How do you debug a input script(that has commands linked to c++ project) using gdb?
You use the gdb run command:
$ gdb lmp_fedora
(gdb) run <in.hit
From the help:
(gdb) help run
Start debugged program. You may specify arguments to give it.
Args may include "*", or "[...]"; they are expanded using "sh".
Input and output redirection with ">", "<", or ">>" are also allowed.
With no arguments, uses arguments last specified (with "run" or "set args").
To cancel previous arguments and run with no arguments,
use "set args" without arguments.
When you say gdb foo < bar that means bar is input to gdb, not to foo.
I think what you want to use is the gdb command set args.
How do you run GDB while allowing interactive entry of characters from the command line while simultaneosuly "printing" the values of the variables arising from the parsed characters from those entries?
In other words how do I run gdb, enter text into the command line AND see how the executable treats those entries?
Also is there any difference in the behavior of gdb if I run it from within Emacs with M-x gdb? Suspending the executable with C-c C-c and then trying to print variable values does not behave like I expected. It did not seem to recognize valid variable values from the suspended executable being debugged. I did generate a "debuggable" excutable from Clang with -ggdb -O0 flags.
I also tried to link gdb to the pid of the program executable running in a separate terminal but still am having difficulty with it. The program needs to parse command line entries interactively; I cannot pass them as initial command line arguments.
I hope I made my question clear.
After you started M-x gdb enter M-x gdb-many-windows . This opens new windows in your frame which show the stack, breakpoints, locals, your code and I/O of your program, meaning if you type there the input will be given to your executable.
I am using gdb to debug NS-2 which is a simulator for network protocols. It takes an .tcl file as input and interpret it. [I think it is an interpreter.]
Some of the code is written in tcl (events and creation of network components) and some in C++ (especially Packet Formats, Agents etc.).
I have created an Agent in C++ and i want to stop it at some function call so that i can see the stack trace and find which other classes have been called before it.
This is what i have done:
There was some error in one of my MyAgent::function and it was giving Segmentation Fault and gdb was stopping there automatically. I could then see the stack trace. I rectified the error.
Now when i run
gdb ./ns
b MyAgent::function()
/*
When i press TAB after writing "b MyA" it gives me all functions
of my class :). when i press enter after above command --
it asks me "Breakpoint on future shared library load" and i say Yes.
I hope this is ok ??
*/
r myfiles/myWireless.tcl
Now it runs and do not stop anywhere. :(
I am sure that this function is being called, because when that Segmentation fault was occuring, it was stopping at that function.
Thanks
You can add a breakpoint in that function:
(gdb) break MyAgent::function()
You must make sure to compile with whatever options are necessary to get debug symbols. On GCC, use the -g or -ggdb options.
You need the -args option to specify the tcl script that will be executed.
Run gdb like this:
gdb -args ./ns path/to/tcl/script.tcl
To enable debug flag to c++ code, if have not done it already, re-configure your ns2 instalation with:
./configure --enable-debug ;# plus any other flags you use for configuring
make clean
make -j 3 ;# -j for faster compiling
make install ;# optional
You can also use the --with-tcldebug=..., for debugging tcl code (You need to install tcldebug first for this option)