Mex debugging keeps crashing

Hi

I'm following the instructions here to debug yprime.c, but Matlab crashes each and every time on execution. I'm running R2017a on Ubuntu 16.04.

What I've done is:

1) Run matlab -Dgdb

2) gdb: handle SIGSEGV SIGBUS nostop noprint

3) gdb: run -nojvm

4) >> dbmex on

5) >> yprime(1,1:4)

I then immediately get the following error:

MEX FILE: /home/jk/Projects/test/yprime.mexa64 entry point located at address 0xbaaf4bb9
Add breakpoints at the debugger prompt and issue a "continue" to resume 
execution of MATLAB.

Thread 1 "MATLAB" received signal SIGUSR1, User defined signal 1.
pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
185  ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S: No such file or directory.

'bt full' gives the following:

(gdb) bt full
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
No locals.
#1  0x00007fffe4af5b73 in ?? () from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwmcr.so
No symbol table info available.
#2  0x00007fffe4af6d64 in ?? () from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwmcr.so
No symbol table info available.
#3  0x00007fffe4af70e3 in mcr_run_main(boost::function0<int> const&, bool, bool) ()
   from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwmcr.so
No symbol table info available.
#4  0x00007fffe57b62d8 in ?? () from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwMVMLocal.so
No symbol table info available.
#5  0x00007ffff62604dd in ?? () from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwmvm.so
No symbol table info available.
#6  0x00007ffff62609ae in ?? () from /usr/local/MATLAB/R2017a/bin/glnxa64/libmwmvm.so
No symbol table info available.
#7  0x0000000000406080 in ?? ()
No symbol table info available.
#8  0x00007ffff47b6830 in __libc_start_main (main=0x405d70, argc=2, argv=0x7fffffffe2b8, 
    init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe2a8)
    at ../csu/libc-start.c:291
        result = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 7758931341986087730, 4219416, 140737488347824, 
                0, 0, -7758930796045810894, -7758951716631231694}, mask_was_saved = 0}}, priv = {
---Type <return> to continue, or q <return> to quit---
            {0x0, 0x0, 0x2, 0x405d70}, data = {prev = 0x0, cleanup = 0x0, canceltype = 2}}}
        not_first_call = <optimized out>
#9  0x0000000000406241 in ?? ()
No symbol table info available.

Anyone know why Matlab keeps crashing?

Any thought appreciated.