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Answer a common FAQ:
"Can I compile C or C++ code to platform-independent LLVM bitcode?" git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64222 91177308-0d34-0410-b5e6-96231b3b80d8
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<li><a href="#translatecxx">Can I use LLVM to convert C++ code to C code?</a></li>
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<li><a href="#platformindependent">Can I compile C or C++ code to platform-independent LLVM bitcode?</a></li>
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</ol>
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</li>
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@ -629,6 +631,31 @@ with standard C++ libraries.</p>
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</div>
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<div class="question">
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<p>
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<a name="platformindependent">Can I compile C or C++ code to platform-independent LLVM bitcode?</a>
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</p>
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</div>
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<div class="answer">
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<p>No. C and C++ are inherently platform-dependent languages. The most
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obvious example of this is the preprocessor. A very common way that C code
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is made portable is by using the preprocessor to include platform-specific
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code. In practice, information about other platforms is lost after
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preprocessing, so the result is inherently dependent on the platform that
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the preprocessing was targetting.</p>
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<p>Another example is <tt>sizeof</tt>. It's common for <tt>sizeof(long)</tt>
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to vary between platforms. In most C front-ends, <tt>sizeof</tt> is expanded
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to a constant immediately, thus hardwaring a platform-specific detail.</p>
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<p>Also, since many platforms define their ABIs in terms of C, and since
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LLVM is lower-level than C, front-ends currently must emit platform-specific
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IR in order to have the result conform to the platform ABI.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="cfe_code">Questions about code generated by the GCC front-end</a>
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