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Compiling Mozilla's "rr" (record/replay) source debugger

First change directory to a convenient place for cloned repo's and builds. Then clone the RR repository from github:

git clone http://github.com/mozilla/rr.git

Optionally do : mkdir ~/local if you want a non-root install.

Note the wiki on GitHub has expansive instructions on building the rr binaries:

https://github.com/mozilla/rr/wiki/Building-And-Installing#hardwaresoftware-requirements

Do this to install prerequisites for building rr:

sudo apt-get install ccache cmake make g++-multilib gdb \
  pkg-config realpath python-pexpect manpages-dev git \
  ninja-build capnproto libcapnp-dev

Also included on the wiki page is a pointer to how to build capnproto from scratch, necessary if using earlier than Ubuntu 16 . Follow the excerpt below, or get fuller instructions from the included link:

https://capnproto.org/install.html#installation-unix

So pause right here to build capnproto if you're using Ubuntu 14 (or less recent) :

curl -O https://capnproto.org/capnproto-c++-0.6.1.tar.gz
tar zxf capnproto-c++-0.6.1.tar.gz
cd capnproto-c++-0.6.1
./configure
make -j6 check
sudo make install

Now, cd .. to escape the capnproto build directory (if you performed that step) and make a build directory parallel to the rr directory: mkdir build_rr

And:

$ cd build_rr
$ CC=clang CXX=clang++ cmake -G Ninja -Ddisable32bit=ON ../rr

The commands above configure the rr build to use the toolchain found under the /opt/irods-externals folder (cmake and clang). Make sure that the /opt/irods-externals folders are in the $PATH environment before /bin and/or /usr/bin.

This will build rr:

$ ninja all

And, now that rr has been built, test it and install it using sudo. (Note that tuning the perf_event_paranoid kernel parameter may be necessary first. Directions at the foot of this section[1].

To test:

$ ninja test

The test runs (more than a thousand of them at this time) take a few minutes to complete, and should all pass.

The installation of rr should target /usr/local/ (the default action), not your local file space, since there it may be used by more than one user:

$ sudo ninja install

To install rr locally under your home directory, make the following changes to the process above:

Add the following flag to the cmake command (use any path that you can write to):

-DCMAKE_INSTALL_PREFIX:PATH=$HOME/local

And, run the install process without using sudo:

$ ninja install

Sample use is (under bash, and optionally putting first line of below into your ~/.bashrc so you don't have to type it every time):

export PATH=$HOME/local/bin:$PATH #non-root install only
rr record -w  <cmd args...>
rr ps
rr replay -f <pid>

NOTE w.r.t. debugging the iRODS server(s) using rr: The last of the commands given just above does the replay for the case of an iRODS server (vsn >=4.2) in which agents are spawned using only a fork() system call. In earlier versions (<=4.1) , agents were spawned with a fork() followed by exec() and thus the -p switch should be used in place of -f.

(The -w in the first command apparently prevents the debugging from exiting in the case it aborts or exits with subprocesses still running.)

FootNotes

[1] On Linux based platforms , following these instructions may be necessary before testing or running the newly built rr.

  • We must modify a kernel parameter which may be set too high by default for rr's proper functioning. Edit the /etc/sysctl.conf to include the following line:
    kernel.perf_event_paranoid = -1
  • Although any value less than 2 should do.
  • To force the system to pick up this change, either do sysctl -p as root, or reboot the machine.