Ichthyostega
109d682408
Knowledge-Technology(Claude Opus 5) used - to assess the situation and present implementation avenues - for discussion while shaping the solution - for generating code and validating results Clang based tooling is used frequently for code analysis and navigation. This requires however that the exact flags and invocation is captured for each possible translation unit in the code base. That knowledge exists solely in the build system, and the established way to hand it over is the LLVM "JSON Compilation Database". SCons has provided a `CompilationDatabase` builder since 4.0, and it fits our setup well: it installs an emitter on the object builders and captures each command line while the dependency graph is constructed. Hence nothing is compiled -- generating takes about two seconds -- and the result always describes the complete build graph as declared, rather than the target actually requested on this invocation. This feature is provided as ''opt-in'', either through the sticky option `COMPILEDB=yes` or by direct invocation with `scons compiledb` The `compile_commands.json` is generated into the build output `target/' dir For configuration, a `.clangd` in project root instructs the language server where to find this file. __Note__ the ordering constraint recorded in `CompileDB.py`: the emitter must be installed only after `Platform.configure()` has run, or it also captures the `conftest_*` compilations of the configure checks. That is why this is a plain helper invoked from the `SConstruct` -- similar to Setup, Options, Platform -- and not a tool loaded from the `LumieraEnvironment`.
59 lines
3 KiB
Python
59 lines
3 KiB
Python
# coding: utf-8
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##
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## CompileDB.py - SCons build: generate a compilation database for clangd
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##
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# Copyright (C)
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# 2026, Hermann Vosseler <Ichthyostega@web.de>
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#
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# **Lumiera** is free software; you can redistribute it and/or modify it
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# under the terms of the GNU General Public License as published by the
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# Free Software Foundation; either version 2 of the License, or (at your
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# option) any later version. See the file COPYING for further details.
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#####################################################################
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from SCons.Script import COMMAND_LINE_TARGETS
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def setup(env):
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""" Emit a *compilation database*, describing every compiler invocation of the
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complete build. This JSON file is the interface used by `clangd` and the other
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tools built on the Clang front-end, which need to reproduce the exact flags
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of a translation unit in order to parse it the way the build does.
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The actual work is performed by the `CompilationDatabase` builder, which SCons
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provides since 4.0: it installs an additional *emitter* on the object builders,
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capturing each command line while the dependency graph is constructed. Thus no
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compilation is involved -- `scons compiledb` takes about two seconds -- and the
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database always covers the *complete declared build*, not just the requested
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target, since the SConscript definitions are processed into a dependency tree
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on every invocation anyway.
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@return a dependency node, to be added to the `build` alias, or an empty list
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when the feature is switched off (in which case nothing at all is
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installed into the build environment).
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@note **must be invoked after** `Platform.configure(env)`. The emitter would
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otherwise also capture the `conftest_*` compilations performed by the
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configure checks, which then show up as bogus entries below '.sconf_temp'.
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This ordering constraint is why this module is a plain helper invoked
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from the 'SConstruct' -- like `Setup`, `Options` and `Platform` -- and
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not a SCons tool loaded from the `LumieraEnvironment` constructor.
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@remark the database is written into the (relocatable) target tree, while the
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'.clangd' configuration in the project root directs the language server
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there; consumers do not search 'target/' on their own.
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"""
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if not isActivated(env): return []
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env.Tool('compilation_db') # the builder provided by SCons
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env['COMPILATIONDB_USE_ABSPATH'] = True # make recorded content unambiguous
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compileDB = env.CompilationDatabase('$TARGDIR/compile_commands.json')
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env.Alias('compiledb', compileDB)
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return compileDB
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def isActivated(env):
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""" generation is opt-in through the (sticky) build option,
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but can also be requested for a single invocation by naming the target.
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"""
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return env['COMPILEDB'] or 'compiledb' in COMMAND_LINE_TARGETS
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