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Git Usage: Merging and Rebasing

Read this article for an in-depth discussion on git best practices.

Try to keep your history as simple as possible. Avoid merges on private code unless there is a particularly good reason to. Instead of merging in rootpy/master to update your local branch, use rebase instead. Merging in rootpy/master risks creating criss-cross merges which means you can actually lose code if you're not careful. Git's merging algorithm is actually quite dumb, so it's best to keep it simple.

See rootpy's network for a graphical view of rootpy's entire history:

https://github.com/rootpy/rootpy/network

Let's all try our best to keep this graph as clean as possible.

Coding Guidlines

TODO

Writing Documentation

TODO

See docs/README

Submodules

To initialize submodules and update to the currently referenced commit:

git submodule init
git submodule update

Developer notes

Using a debug python build

The following CPython configure arguments can be used to obtain a debug build:

python-6.6.6/build $ ../configure --enable-shared --with-pydebug --without-pymalloc --prefix=install/path

But beware! You will need to build ROOT against this python build. And beware that GDB might be linked against python. If that's the case, then it will segfault when it starts if it picks up an incompatible build:

$ gdb
gdb: Symbol `_Py_ZeroStruct' has different size in shared object, consider re-linking
gdb: Symbol `PyBool_Type' has different size in shared object, consider re-linking
gdb: Symbol `_Py_NotImplementedStruct' has different size in shared object, consider re-linking
gdb: Symbol `PyFloat_Type' has different size in shared object, consider re-linking
gdb: Symbol `_Py_TrueStruct' has different size in shared object, consider re-linking
gdb: Symbol `_Py_NoneStruct' has different size in shared object, consider re-linking
Segmentation fault

The way around this is to preload the correct library by setting LD_PRELOAD, and then unsetting it before your program is executed. For example, this will debug my-program-to-debug:

LD_PRELOAD=/usr/lib/libpython2.7.so gdb -ex 'set environ LD_PRELOAD' --args my-program-to-debug

Note that you need to set LD_PRELOAD to the right version of python that gdb was compiled against, which you can find with ldd $(which gdb) from a fresh environment.