The
cppyy
module is a frontend that requires an intermediate (Python interpreter dependent) layer, and a backend (see
Package Structure
). Because of this layering and because it leverages several existing packages through reuse, the relevant codes are contained across a number of repositories.
The backend repo contains both the cppyy-cling (under “cling”) and cppyy-backend (under “clingwrapper”) packages.
Except for cppyy-cling, the structure in the repositories follows a normal PyPA package and they are thus ready to build with
setuptools
: simply clone the package and either run
python setup.py
，或使用
pip
.
It is highly recommended to follow the dependency chain when manually upgrading packages individually (i.e.
cppyy-cling
,
cppyy-backend
,
CPyCppyy
if on CPython, and then finally
cppyy
), because upstream packages expose headers that are used by the ones downstream. Of course, if only building for a patch/point release, there is no need to re-install the full chain (or follow the order). Always run the local updates from the package directories (i.e. where the
setup.py
file is located), as some tools rely on the package structure.
The
STDCXX
envar can be used to control the C++ standard version; use
MAKE
to change the
make
command; and
MAKE_NPROCS
to control the maximum number of parallel jobs. Compilation of the backend, which contains a customized version of Clang/LLVM, can take a long time, so by default the setup script will use all cores (x2 if hyperthreading is enabled).
On MS Windows, some temporary path names may be too long, causing the build to fail. To resolve this issue, point the
TMP
and
TEMP
envars to an existing directory with a short name before the build: For example:
> set TMP=C:\TMP > set TEMP=C:\TMP
Start with the
cppyy-cling
package (cppyy-backend repo, subdirectory “cling”), which requires source to be pulled in from upstream, and thus takes a few extra steps:
$ git clone https://github.com/wlav/cppyy-backend.git $ cd cppyy-backend/cling $ python setup.py egg_info $ python create_src_directory.py $ python -m pip install . --upgrade
The
egg_info
setup command is needed for
create_src_directory.py
to find the right version. That script in turn downloads the proper release from
upstream
, trims and patches it, and installs the result in the “src” directory. When done, the structure of
cppyy-cling
looks again like a PyPA package and can be used/installed as expected, here using
pip
.
The
cppyy-cling
package, because it contains Cling/Clang/LLVM, is rather large to build, so by default the setup script will use all cores (x2 if hyperthreading is enabled). You can change this behavior with the
MAKE_NPROCS
envar. The wheel of
cppyy-cling
is reused by pip for all versions of CPython and PyPy, thus the long compilation is needed only once for all different versions of Python on the same machine.
Next up is
cppyy-backend
(cppyy-backend, subdirectory “clingwrapper”; omit the first step if you already cloned the repo for
cppyy-cling
):
$ git clone https://github.com/wlav/cppyy-backend.git $ cd cppyy-backend/clingwrapper $ python -m pip install . --upgrade --no-use-pep517 --no-deps
Note the use of
--no-use-pep517
, which prevents
pip
from needlessly going out to pypi.org and creating a local “clean” build environment from the cached or remote wheels. Instead, by skipping PEP 517, the local installation will be used. This is imperative if there was a change in public headers or if the version of
cppyy-cling
was locally updated and is thus not available on PyPI.
Upgrading
CPyCppyy
(if on CPython; it’s not needed for PyPy) and
cppyy
is very similar:
$ git clone https://github.com/wlav/CPyCppyy.git $ cd CPyCppyy $ python -m pip install . --upgrade --no-use-pep517 --no-deps
Finally, the top-level package
cppyy
:
$ git clone https://github.com/wlav/cppyy.git $ cd cppyy $ python -m pip install . --upgrade --no-use-pep517 --no-deps
Please see the pip documentation for more options, such as developer mode.
