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| <!--*********************************************************************--> | |
| <h1>Hacking on Clang</h1> | |
| <!--*********************************************************************--> | |
| <p>This document provides some hints for how to get started hacking | |
| on Clang for developers who are new to the Clang and/or LLVM | |
| codebases.</p> | |
| <ul> | |
| <li><a href="#docs">Developer Documentation</a></li> | |
| <li><a href="#debugging">Debugging</a></li> | |
| <li><a href="#testing">Testing</a></li> | |
| <li><a href="#irgen">LLVM IR Generation</a></li> | |
| </ul> | |
| <!--=====================================================================--> | |
| <h2 id="docs">Developer Documentation</h2> | |
| <!--=====================================================================--> | |
| <p>Both Clang and LLVM use doxygen to provide API documentation. Their | |
| respective web pages (generated nightly) are here:</p> | |
| <ul> | |
| <li><a href="http://clang.llvm.org/doxygen">Clang</a></li> | |
| <li><a href="http://llvm.org/doxygen">LLVM</a></li> | |
| </ul> | |
| <p>For work on the LLVM IR generation, the LLVM assembly language | |
| <a href="http://llvm.org/docs/LangRef.html">reference manual</a> is | |
| also useful.</p> | |
| <!--=====================================================================--> | |
| <h2 id="debugging">Debugging</h2> | |
| <!--=====================================================================--> | |
| <p>Inspecting data structures in a debugger:</p> | |
| <ul> | |
| <li>Many LLVM and Clang data structures provide | |
| a <tt>dump()</tt> method which will print a description of the | |
| data structure to <tt>stderr</tt>.</li> | |
| <li>The <a href="docs/InternalsManual.html#QualType"><tt>QualType</tt></a> | |
| structure is used pervasively. This is a simple value class for | |
| wrapping types with qualifiers; you can use | |
| the <tt>isConstQualified()</tt>, for example, to get one of the | |
| qualifiers, and the <tt>getTypePtr()</tt> method to get the | |
| wrapped <tt>Type*</tt> which you can then dump.</li> | |
| </ul> | |
| <!--=====================================================================--> | |
| <h2 id="testing">Testing</h2> | |
| <!--=====================================================================--> | |
| <p>Clang includes a basic regression suite in the tree which can be | |
| run with <tt>make test</tt> from the top-level clang directory, or | |
| just <tt>make</tt> in the <em>test</em> sub-directory. <tt>make | |
| report</tt> can be used after running the tests to summarize the | |
| results, and <tt>make VERBOSE=1</tt> can be used to show more detail | |
| about what is being run.</p> | |
| <p>For more intensive changes, running | |
| the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM | |
| Test Suite</a> with clang is recommended. Currently the best way to | |
| override LLVMGCC, as in: <tt>make LLVMGCC="ccc -std=gnu89" | |
| TEST=nightly report</tt> (make sure ccc is in your PATH or use the | |
| full path).</p> | |
| <!--=====================================================================--> | |
| <h2 id="irgen">LLVM IR Generation</h2> | |
| <!--=====================================================================--> | |
| <p>The LLVM IR generation part of clang handles conversion of the | |
| AST nodes output by the Sema module to the LLVM Intermediate | |
| Representation (IR). Historically, this was referred to as | |
| "codegen", and the Clang code for this lives | |
| in <tt>lib/CodeGen</tt>.</p> | |
| <p>The output is most easily inspected using the <tt>-emit-llvm</tt> | |
| option to clang (possibly in conjunction with <tt>-o -</tt>). You | |
| can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file | |
| which can be processed by the suite of LLVM tools | |
| like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM | |
| <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a> | |
| for more information.</p> | |
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