78 lines
3.0 KiB
Plaintext
78 lines
3.0 KiB
Plaintext
Copyright 2005 Vladimir Prus
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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Summary
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-------
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We need a --build-dir option that users building from read-only
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medium can use to force building to some other location. Pretty much
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every project need this functionality, so it's desirable to have it
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out-of-the box, without explicit setup.
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Design
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------
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We can achieve the desired effect manually by adding something like this
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to Jamroot:
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project .... : build-dir [ my-rule-to-compute-build-dir ] ;
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Where 'my-rule-to-compute-build-dir' would look at the --build-dir option.
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We need to automate this, but essentially, --build-dir will only affect
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the 'build-dir' attribute of Jamroots.
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If Jamroot contains:
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project foo ;
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and --build-dir options' value if /tmp/build, then we'll act as if Jamroot
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contained:
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project foo : build-dir /tmp/build/foo ;
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If the 'project' rule has explicit 'build-dir':
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project foo : build-dir bin.v2 ;
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then with the same value of --build-dir we'd act as if Jamroot contained:
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project foo : build-dir /tmp/build/foo/bin.v2 ;
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We can't drop "bin.v2" because it's quite possible that the name of build dir
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have specific meaning. For example, it can be used to separate Boost.Build V1
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and V2 build results.
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The --build-dir option has no effect if Jamroot does not define any project id.
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Doing otherwise can lead to nasty problems if we're building two distinct
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projects (that is with two different Jamroot). They'll get the same build
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directory. Most likely, user will see the "duplicate target" error, which is
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generally confusing.
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It is expected that any non-trivial project will have top-level "project"
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invocation with non empty id, so the above limitation is not so drastic.
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We'll emit a warning if Jamroot does not define project id, and --build-dir
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is specified.
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Here's the exact behavior of the --build-dir option. If we're loading a
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Jamfile (either root or non-root), that declare some project id and some
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build-dir attribute, the following table gives the value of build-dir
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that will actually be used.
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-------------------------------------------------------------------------------
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Root? Id Build-dir attribute Resulting build dir
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-------------------------------------------------------------------------------
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yes none * --build-dir is ignored, with warning
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yes 'foo' none /tmp/build/foo
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yes 'foo' 'bin.v2' /tmp/build/foo/bin.v2
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yes 'foo' '/tmp/bar' Error [1]
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no * none --build-dir has no effect, inherited
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build dir is used
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no * non-empty Error [2]
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-------------------------------------------------------------------------------
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[1] -- not clear what to do
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[2] -- can be made to work, but non-empty build-dir
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attribute in non-root Jamfile does not make much sense even without --build-dir
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