You can use Python as a scripting language in gdb to find the PID of a
currently running MATLAB process and attach to it. I remember doing this a
while back. The code was something around the lines of:
<code>
# debugging MEX files in emacs on linux
import sys
pythondir = '/usr/share/gcc-6.2.1/python'
sys.path.append(pythondir)
from libstdcxx.v6 import register_libstdcxx_printers
from subprocess import check_output
try:
register_libstdcxx_printers(None)
except Exception as e:
pass
# find the PID of the MATLAB process
def get_pid(name):
return list(map(int, check_output(["pidof", name]).split()))
# set a new breakpoint, deleting any breakpoints referring to the same location
def new_bp(loc):
bps = gdb.breakpoints()
if bps:
for bp in bps:
if bp.location == loc:
gdb.execute("d " + str(bp.number))
# set the dummy breakpoint
return gdb.Breakpoint(loc)
# attach to the MATLAB process. if gdb attach fails, do
# sudo sh -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
pids = get_pid("MATLAB")
gdb.execute("attach {:d}".format(pids[0]))
<end code>
an alternative approach is to launch matlab from gdb:
<code>
run_matlab = True
if run_matlab:
# spawn a new MATLAB process
matlab_dir = "/path/to/MATLAB/R2016b/bin/glnxa64/MATLAB"
gdb.execute("file " + matlab_dir)
# set the MATLAB_DEBUG env
gdb_loc = "/usr/bin/gdb"
gdb.execute("set environment MATLAB_DEBUG = " + gdb_loc)
# need to execute this according to
#
https://www.mathworks.com/help/matlab/matlab_external/debugging-on-linux-platforms.html
gdb.execute("handle SIGSEGV SIGBUS nostop noprint")
# set the breakpoint at the mexFunction
mex_Bp = new_bp("mexFunction")
# run matlab
gdb.execute("run -nojvm -r debug_encoder -singleCompThread")
<end code>
Dennis
Dong Tian <t...@merl.com> writes:
> Hi Eric, all,
>
> Thanks for replying.
>
> It is non-trivial to attach the matlab process to gdb.
>
> Matlab provides a command line option -Dgdb to associate the Matlab process
> for gdb debugging. Would it be easier to launch "matlab-shell" with -Dgdb
> as option? Maybe your or someone else could put lights on this approach?
>
> Thanks,
> Dong
>
> On Wed, Jul 19, 2017 at 09:01:56PM +0000, Eric Ludlam wrote:
>> Hi Dong,
>>
>> You can fire up GDB from within Emacs and "attach" to a process. Using
>> this to attach to a process running MATLAB inside Emacs' matlab-shell will
>> let you debug through MATLAB code and into your C++ code.
>>
>> I haven't done this in a few years, and not with Mex (I was debugging MATLAB
>> directly) but I'm guessing the principle is the same.
>>
>> Eric
>>
>> -----Original Message-----
>> From: Dong Tian [mailto:t...@merl.com]
>> Sent: Wednesday, July 19, 2017 1:56 PM
>> To: matlab-emacs-discuss@lists.sourceforge.net
>> Subject: [Matlab-emacs-discuss] How to debug MEX files (C code) from Emacs?
>>
>> Hello,
>>
>> Could anyone provide a pointer on how to debug MEX files from Emacs?
>> E.g. using gdb?
>>
>> I am familiar with the procedure of debugging pure c/c++ code or .m code
>> from Emacs using gdb, but I don't know a good way to debug MEX file coded in
>> C from Emacs.
>>
>> Thanks in advance,
>> Dong
>>
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