WSJT-X/boost/tools/build/notes/relative_source_paths.txt

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Copyright 2005 Vladimir Prus
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
Hi,
recently, we had a couple of problems caused by using relative file paths, and
I'd like to discuss what to do.
Let's use the case from CÊdric. Simplified version is:
exe a : a.cpp dir1/qt_file.h ;
exe b : a.cpp dir2/qt_file.h ;
Both exes have the same source cpp file but different *.h files -- which are
processed by Qt tools. V2 currently strips directory name from all targets,
so it tries to
- create "bin/mvsc/debug/moc_qt_file.cpp" from dir1/qt_file.h
- create "bin/msvc/debug/moc_qt_file.cpp" from dir2/qt_file.h
There are two solutions that I see:
1. Rewrite the code like:
lib aux : a.cpp
exe a : aux dir1/qt_file.h : <location-prefix>a ;
exe b : aux dir2/qt_file.h : <location-prefix>b ;
This way, two version of moc_qt_file.cpp will be generated to different
places.
2. Rewrite the code like:
obj a_moc : dir1/qt_file.h : <library>/qt//qt ;
exe a : a.cpp a_moc ;
obj b_moc : dir2/qt_file.h : <library>/qt//qt ;
exe b : a.cpp b_moc ;
Explicitly changing name for the problematic files.
3. Generally change V2 so that directory part of source is preserved. This
will generate targets:
"bin/msvc/debug/dir1/moc_qt_file.cpp" and
"bin/msvc/debug/dir2/moc_qt_file.cpp". No problems.
However, there are some additional questions:
- What if source has absolute file name?
- What if source is "../../include/qt_file.h"?
We can ignore directory names in those cases (i.e. use the current
behaviour) but that would be a bit inconsistent.
Any opinions?
Pedro Ferreira:
I think this is a corner case and BB should not try to solve everything
automatically - otherwise it will become really complex.
I don't see a problem in requiring the user to help the build system by
using solutions 1 or 2.
Of course, the better the error reporting, the easier it will be to
find the cause and the cure of the problem.
TEMPLIE Cedric:
I agree with Pedro. Solution 1 or 2 is the best way to deal with this
problem. Of course I have a preference for the solution 1, but the
solution 2 has the advantage to work without any modification...
Toon Knapen:
I agree.