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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+
+<h1>
+<center>
+LLVM: Frequently Asked Questions
+</center>
+</h1>
+
+<hr>
+
+<!--=====================================================================-->
+<h2>
+<a name="source">Source Code</a>
+</h2>
+<!--=====================================================================-->
+
+<dl compact>
+ <dt> <b>In what language is LLVM written?</b>
+ <dd>
+ All of the LLVM tools and libraries are written in C++ with extensive use
+ of the STL.
+ <p>
+
+ <dt><b>How portable is the LLVM source code?</b>
+ <dd>
+ The LLVM source code should be portable to most modern UNIX-like operating
+ systems. Most of the code is written in standard C++ with operating
+ system services abstracted to a support library. The tools required to
+ build and test LLVM have been ported to a plethora of platforms.
+ <p>
+ Some porting problems may exist in the following areas:
+ <ul>
+ <li>The GCC front end code is not as portable as the LLVM suite, so it
+ may not compile as well on unsupported platforms.
+
+ <p>
+
+ <li>The Python test classes are more UNIX-centric than they should be,
+ so porting to non-UNIX like platforms (i.e. Windows, MacOS 9) will
+ require some effort.
+ <p>
+
+ <li>The LLVM build system relies heavily on UNIX shell tools, like the
+ Bourne Shell and sed. Porting to systems without these tools (MacOS 9,
+ Plan 9) will require more effort.
+ </ul>
+</dl>
+
+<hr>
+
+<!--=====================================================================-->
+<h2>
+<a name="build">Build Problems</a>
+</h2>
+<!--=====================================================================-->
+
+<dl compact>
+ <dt><b>When I run configure, it finds the wrong C compiler.</b>
+ <dd>
+ The <tt>configure</tt> script attempts to locate first <tt>gcc</tt> and
+ then <tt>cc</tt>, unless it finds compiler paths set in <tt>CC</tt> and
+ <tt>CXX</tt> for the C and C++ compiler, respectively.
+
+ If <tt>configure</tt> finds the wrong compiler, either adjust your
+ <tt>PATH</tt> environment variable or set <tt>CC</tt> and <tt>CXX</tt>
+ explicitly.
+ <p>
+
+ <dt><b>I compile the code, and I get some error about /localhome</b>.
+ <dd>
+ There are several possible causes for this. The first is that you
+ didn't set a pathname properly when using <tt>configure</tt>, and it
+ defaulted to a pathname that we use on our research machines.
+ <p>
+ Another possibility is that we hardcoded a path in our Makefiles. If
+ you see this, please email the LLVM bug mailing list with the name of
+ the offending Makefile and a description of what is wrong with it.
+
+ <dt><b>The <tt>configure</tt> script finds the right C compiler, but it
+ uses the LLVM linker from a previous build. What do I do?</b>
+ <dd>
+ The <tt>configure</tt> script uses the <tt>PATH</tt> to find
+ executables, so if it's grabbing the wrong linker/assembler/etc, there
+ are two ways to fix it:
+ <ol>
+ <li>Adjust your <tt>PATH</tt> environment variable so that the
+ correct program appears first in the <tt>PATH</tt>. This may work,
+ but may not be convenient when you want them <i>first</i> in your
+ path for other work.
+ <p>
+
+ <li>Run <tt>configure</tt> with an alternative <tt>PATH</tt> that
+ is correct. In a Borne compatible shell, the syntax would be:
+ <p>
+ <tt>PATH=<the path without the bad program> ./configure ...</tt>
+ <p>
+ This is still somewhat inconvenient, but it allows
+ <tt>configure</tt> to do its work without having to adjust your
+ <tt>PATH</tt> permanently.
+ </ol>
+
+ <dt><b>When creating a dynamic library, I get a strange GLIBC error.</b>
+ <dd>
+ Under some operating systems (i.e. Linux), libtool does not work correctly
+ if GCC was compiled with the --disable-shared option. To work around this,
+ install your own version of GCC that has shared libraries enabled by
+ default.
+ <p>
+
+ <dt><b>I've updated my source tree from CVS, and now my build is trying to
+ use a file/directory that doesn't exist.</b>
+ <dd>
+ You need to re-run configure in your object directory. When new Makefiles
+ are added to the source tree, they have to be copied over to the object
+ tree in order to be used by the build.
+ <p>
+
+ <dt><b>I've modified a Makefile in my source tree, but my build tree keeps
+ using the old version. What do I do?</b>
+ <dd>
+ If the Makefile already exists in your object tree, you can just run the
+ following command in the top level directory of your object tree:
+ <p>
+ <tt>./config.status <relative path to Makefile></tt>
+ <p>
+ If the Makefile is new, you will have to modify the configure script to copy
+ it over.
+ <p>
+
+ <dt><b>I've upgraded to a new version of LLVM, and I get strange build
+ errors.</b>
+ <dd>
+ Sometimes changes to the LLVM source code alters how the build system
+ works. Changes in libtool, autoconf, or header file dependencies are
+ especially prone to this sort of problem.
+ <p>
+ The best thing to try is to remove the old files and re-build. In most
+ cases, this takes care of the problem. To do this, just type <tt>make
+ clean</tt> and then <tt>make</tt> in the directory that fails to build.
+ <p>
+</dl>
+<hr>
+
+</body>
+</html>
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