Re: [PATCH] Makefile: Remove excess backslashes from sed

> Brian Gernhardt <brian@gernhardtsoftware.com> writes:
> 
> > The sed script that was intended to add lines altering the sys.path
> > had extra backslashes in them.  Instead resulting in
> >
> >   import sys;  import os;  sys.path.insert( ... )
> >
> > It output
> >
> >   import sys; \ import os; \ sys.path.insert( ... )
> >
> > Unfortunately this caused python (2.6.1 on OS X 10.6.3) to error
> >
> >   SyntaxError: unexpected character after line continuation character
> >
> > Removing two of the backslashes solves this problem.
> 
> Traditionally, multi-line sed statements written in the Makefile were
> portability nightmare, as the line folding rules (especially how the
> backslash is treated in the output) in make implementations were subtly
> different, and implementations of sed also got multi-line statement often
> wrong.  These days, things might have gotten much better, but in olden
> days (back when BSD vs SysV war was still raging), the trick to write
> things like this portably was to invoke a shell script that has multi-line
> sed statement from the Makefile.  It was painful.
> 
> I wonder if we can make this a lot simpler to avoid multi-line sed script.
> For example, we could write the source Python script to always begin with:
> 
> 	#!/usr/bin/python
>         import sys;
>         import os;
>         sys.path.insert(0, os.getenv("GITPYTHONLIB","."));
> 
> and then do something like this in the Makefile:
> 
> 	INSTLIBDIR=... && \
> 	sed -e '1s|#!.*python|#!$(PYTHON_PATH_SQ)|' \
>         -e 's|\(os\.getenv("GITPYTHONLIB"\)[^)]*)|\1,"'"$$INSTLIBDIR"'")|' \
>         <$@.py >$@+
> 	mv $@+ $@
> 
> Contributors can then run things in-place while developing the scripts,
> perhaps setting GITPYTHONLIB to the source area.