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| author | Chris Lattner <sabre@nondot.org> | 2006-07-19 18:19:59 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2006-07-19 18:19:59 +0000 |
| commit | 7b1d3c0a9d55a1b65ce4eeea21a57b44092a48e9 (patch) | |
| tree | c4d1183809758aec64fc6235e03a923928186b1d /llvm/docs/FAQ.html | |
| parent | 18debc21db3a51f92c023f129f32a10832e5402b (diff) | |
| download | bcm5719-llvm-7b1d3c0a9d55a1b65ce4eeea21a57b44092a48e9.tar.gz bcm5719-llvm-7b1d3c0a9d55a1b65ce4eeea21a57b44092a48e9.zip | |
Answer the FAQ: "can llvm convert C++ code to C?"
llvm-svn: 29212
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| -rw-r--r-- | llvm/docs/FAQ.html | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/llvm/docs/FAQ.html b/llvm/docs/FAQ.html index e015f91df54..2ab00ac7e90 100644 --- a/llvm/docs/FAQ.html +++ b/llvm/docs/FAQ.html @@ -79,6 +79,8 @@ How can I disable all optimizations when compiling code using the LLVM GCC front end? </li> + <li><a href="#translatec++">Can I use LLVM to convert C++ code to C code?</a></li> + </ol> </li> @@ -501,6 +503,61 @@ code that you desire. </p> </div> + +<div class="question"> +<p> +<a name="translatec++">Can I use LLVM to convert C++ code to C code?</a> +</p> +</div> + +<div class="answer"> +<p>Yes, you can use LLVM to convert code from any language LLVM supports to C. +Note that the generated C code will be very low level (all loops are lowered +to gotos, etc) and not very pretty (comments are stripped, original source +formatting is totally lost, variables are renamed, expressions are regrouped), +so this may not be what you're looking for. However, this is a good way to add +C++ support for a processor that does not otherwise have a C++ compiler. +</p> + +<p>Use commands like this:</p> + +<ol> +<li><p>Compile your program as normal with llvm-g++:</p></li> + +<div class="doc_code">$ llvm-g++ x.cpp -o program</div> + +<p>or:</p> + +<div class="doc_code"> + llvm-g++ a.cpp -c + llvm-g++ b.cpp -c + llvm-g++ a.o b.o -o program +</div> + +<p>With llvm-gcc3, this will generate program and program.bc. The .bc file is +the LLVM version of the program all linked together.</p> + +<li><p>Convert the LLVM code to C code, using the LLC tool with the C +backend:</p></li> + +<div class="doc_code">$ llc -march=c program.bc -o program.c</div> + +<li><p>Finally, compile the c file:</p></li> + +<div class="doc_code">$ cc x.c</div> + +</ol> + +<p>Note that, by default, the C backend does not support exception handling. +If you want/need it for a certain program, you can enable it by passing +"-enable-correct-eh-support" to the llc program. The resultant code will +use setjmp/longjmp to implement exception support that is correct but +relatively slow. +</p> +</div> + + + <!-- *********************************************************************** --> <div class="doc_section"> <a name="cfe_code">Questions about code generated by the GCC front-end</a> |

