src/python/bcc/version.py created as part of build

[bolinfest]

I'm on Ubuntu 18.04.1. First, note that the build instructions:

# Trusty and older
VER=trusty
echo "deb http://llvm.org/apt/$VER/ llvm-toolchain-$VER-3.7 main
deb-src http://llvm.org/apt/$VER/ llvm-toolchain-$VER-3.7 main" | \
  sudo tee /etc/apt/sources.list.d/llvm.list
wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-get update

# All versions
sudo apt-get -y install bison build-essential cmake flex git libedit-dev \
  libllvm3.7 llvm-3.7-dev libclang-3.7-dev python zlib1g-dev libelf-dev

# For Lua support
sudo apt-get -y install luajit luajit-5.1-dev

mention Trusty (14.04) and older, so I wasn't sure what to do for 18.04. I ended up copypasta'ing some stuff from the LLVM Debian/Ubuntu nightly packages and created /etc/apt/sources.list.d/llvm.list with the following contents:

# i386 not available
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
# 6.0
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-6.0 main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-6.0 main
# 7
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-7 main
deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-7 main

Then I basically followed the existing instructions, but instead of:

sudo apt-get -y install libllvm3.7 llvm-3.7-dev libclang-3.7-dev

I did:

sudo apt-get -y install libllvm7 llvm7-dev libclang-7-dev

(Note that I originally tried this with 8 instead of 7, but then building bcc failed because the getLocStart() API appears to have been renamed in LLVM 8.)

Now the problem was getting things to build because everything seems hardcoded for LLVM 3.7. I rooted around in CMakeLists.txt and found $LLVM_LIBRARY_DIRS, so adding an extra argument to cmake worked fine:

cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DLLVM_LIBRARY_DIRS=/usr/lib/llvm-7/lib

However, when I was done, git status was not clean, as there was the file src/python/bcc/version.py with the following contents:

__version__ = '0.7.0-8cc0bda6'

Not a huge deal, but it would be nice if this file were either not created, created under build/, or listed in .gitignore.

It would also be nice if the Ubuntu build instructions were updated to call out what to do for versions after Trusty. Hopefully the record of the steps I went through (and the upcoming breaking in LLVM 8) are useful here.

[yonghong-song]

Yes, this can be easily reproduced. Somehow, when I change branch and did a rebuild. This src/python/bcc/version.py will show up. I do not know why either.

[pchaigno]

I noticed that as well, but didn't took the time to debug it. I think it's been happening since #1826 got merged.

[yonghong-song]

@pchaigno Yes, #1826 introduced a version.py in the source tree to generate a version.py at build the directory.

[pchaigno]

Looks like adding that file to .gitignore would be the right fix here since it's generated at build time from version.py.in...?

[bolinfest]

@pchaigno Adding it to .gitignore would certainly be the quickest fix, though it always seems a bit dirty to me to have generated code in the src/ folder as opposed to the build/ folder, but maybe it's not worth the effort to move it?

[pchaigno]

@bolinfest Right, it probably would be best to generate that file in build/. @andihit Was this the intended behavior? Would it be possible to generate version.py in the build directory only?

[yonghong-song]

We could add an entry in .gitignore. But looking at the source code, I don't understand why this can happen? Any idea?

[brendangregg]

this issue is annoying my builds as well...

[andreasgerstmayr]

@pchaigno Basically I followed the same approach as it's used for creating setup.py from setup.py.in (https://github.com/iovisor/bcc/blob/master/src/python/CMakeLists.txt#L14)

Yes, build/ directory would be fine also.
Any idea why the setup.py is cleaned after the build but bcc/version.py is not?

I'll see if I get time in a few days, probably we just need another directory insead of ${CMAKE_CURRENT_BINARY_DIR} in the cmake file.

[mauriciovasquezbernal]

@andihit you are actually generating version.py in the build/ folder, but there is a link between the build/src/python/bcc and the src/python/bcc folders -> https://github.com/iovisor/bcc/blob/master/src/python/CMakeLists.txt#L8.

I think just adding version.py to .gitignore will solve those issues.

[yonghong-song]

Sounds good then, could you submit a pull request for this? Could you double check when we do a make clean, we do clean this file as well? Thanks!

[mauriciovasquezbernal]

I think this can be close after #1989.