[Python-Dev] Bug in build system for cross-platform builds (original) (raw)

R. David Murray rdmurray at bitdance.com
Mon Mar 14 09:26:14 EDT 2016

On Mon, 14 Mar 2016 03:04:08 -0000, "Gregory P. Smith" <greg at krypto.org> wrote:

On Sun, Mar 13, 2016 at 7:41 PM Martin Panter <vadmium+py at gmail.com> wrote:

> On 13 March 2016 at 01:13, Russell Keith-Magee <russell at keith-magee.com> > wrote: > > The patches that I've uploaded to Issue23670 [1] show a full > cross-platform > > [1] http://bugs.python.org/issue23670 > > build process. After you apply that patch, the iOS directory contains a > > meta-Makefile that manages the build process. > > Thanks very much for pointing that out. This has helped me understand > a lot more things. Only now do I realize that the four files generated > by pgen and freezeimportlib are actually already committed into the > Mercurial repository: > > Include/graminit.h > Python/graminit.c > Python/importlib.h > Python/importlibexternal.h > > A question for other Python developers: Why are these generated files > stored in the repository? The graminit ones seem to have been there > since forever (1990). It seems the importlib ones were there due to a > bootstrapping problem, but now that is solved. Antoine > <https://bugs.python.org/issue14928#msg163048> said he kept them in > the repository on purpose, but I want to know why. > > If we ignore the cross compiling use case, would there be any other > consequences of removing these generated files from the repository? > E.g. would it affect the Windows build process? > > I have two possible solutions in mind: either remove the generated > files from the repository and always build them, or keep them but do > not automatically regenerate them every build. Since they are > generated files, not source files, I would prefer to remove them, but > I want to know the consequences first. > They should not be regenerated every build, if they are, that seems like a bug in the makefile to me (or else the timestamp checks that make does vs how your code checkout happened). Having them checked in is convenient for cross builds as it is one less thing that needs a build-host-arch build.

The repo-timestamp problem is addressed by the 'make touch' target.

And yes, checking in these platform-independent artifacts is very intentional: less to build, fewer external dependencies in the build process...you don't need to have python to build python, which you would have to if they were not checked in.

--David

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