-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+ <title>LLVM: Frequently Asked Questions</title>
+ <style type="text/css">
+ @import url("llvm.css");
+ .question { font-weight: bold }
+ .answer { margin-left: 2em }
+ </style>
+</head>
+<body>
-<h1>
-<center>
-LLVM: Frequently Asked Questions
-</center>
-</h1>
+<div class="doc_title">
+ LLVM: Frequently Asked Questions
+</div>
-<hr>
+<ol>
+ <li><a href="#license">License</a>
+ <ol>
+ <li>Why are the LLVM source code and the front-end distributed under different
+ licenses?</li>
+ <li>Does the University of Illinois Open Source License really qualify as an
+ "open source" license?</li>
+ <li>Can I modify LLVM source code and redistribute the modified source?</li>
+ <li>Can I modify LLVM source code and redistribute binaries or other tools
+ based on it, without redistributing the source?</li>
+ </ol></li>
-<!--=====================================================================-->
-<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>
+ <li><a href="#source">Source code</a>
+ <ol>
+ <li>In what language is LLVM written?</li>
+ <li>How portable is the LLVM source code?</li>
+ </ol></li>
-<hr>
+ <li><a href="#build">Build Problems</a>
+ <ol>
+ <li>When I run configure, it finds the wrong C compiler.</li>
+ <li>The <tt>configure</tt> script finds the right C compiler, but it uses the
+ LLVM linker from a previous build. What do I do?</li>
+ <li>When creating a dynamic library, I get a strange GLIBC error.</li>
+ <li>I've updated my source tree from Subversion, and now my build is trying
+ to use a file/directory that doesn't exist.</li>
+ <li>I've modified a Makefile in my source tree, but my build tree keeps using
+ the old version. What do I do?</li>
+ <li>I've upgraded to a new version of LLVM, and I get strange build
+ errors.</li>
+ <li>I've built LLVM and am testing it, but the tests freeze.</li>
+ <li>Why do test results differ when I perform different types of builds?</li>
+ <li>Compiling LLVM with GCC 3.3.2 fails, what should I do?</li>
+ <li>When I use the test suite, all of the C Backend tests fail. What is
+ wrong?</li>
+ <li>After Subversion update, rebuilding gives the error "No rule to make
+ target".</li>
+ <li><a href="#llvmc">The <tt>llvmc</tt> program gives me errors/doesn't
+ work.</a></li>
+ </ol></li>
+
+ <li><a href="#felangs">Source Languages</a>
+ <ol>
+ <li><a href="#langs">What source languages are supported?</a></li>
+ <li><a href="#langhlsupp">What support is there for higher level source
+ language constructs for building a compiler?</a></li>
+ <li><a href="GetElementPtr.html">I don't understand the GetElementPtr
+ instruction. Help!</a></li>
+ </ol>
+
+ <li><a href="#cfe">Using the GCC Front End</a>
+ <ol>
+ <li>
+ When I compile software that uses a configure script, the configure script
+ thinks my system has all of the header files and libraries it is testing
+ for. How do I get configure to work correctly?
+ </li>
+
+ <li>
+ When I compile code using the LLVM GCC front end, it complains that it
+ cannot find libcrtend.a.
+ </li>
+
+ <li>
+ 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>
+
+ <li><a href="#cfe_code">Questions about code generated by the GCC front-end</a>
+ <ol>
+ <li><a href="#iosinit">What is this <tt>llvm.global_ctors</tt> and
+ <tt>_GLOBAL__I__tmp_webcompile...</tt> stuff that happens when I
+ #include <iostream>?</a></li>
+ <li><a href="#codedce">Where did all of my code go??</a></li>
+ <li><a href="#undef">What is this "<tt>undef</tt>" thing that shows up in my code?</a></li>
+ </ol>
+ </li>
+</ol>
+
+<div class="doc_author">
+ <p>Written by <a href="http://llvm.org">The LLVM Team</a></p>
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="license">License</a>
+</div>
+<!-- *********************************************************************** -->
+
+<div class="question">
+<p>Why are the LLVM source code and the front-end distributed under different
+licenses?</p>
+</div>
+
+<div class="answer">
+<p>The C/C++ front-ends are based on GCC and must be distributed under the GPL.
+Our aim is to distribute LLVM source code under a <em>much less restrictive</em>
+license, in particular one that does not compel users who distribute tools based
+on modifying the source to redistribute the modified source code as well.</p>
+</div>
+
+<div class="question">
+<p>Does the University of Illinois Open Source License really qualify as an
+"open source" license?</p>
+</div>
+
+<div class="answer">
+<p>Yes, the license is <a
+href="http://www.opensource.org/licenses/UoI-NCSA.php">certified</a> by the Open
+Source Initiative (OSI).</p>
+</div>
+
+<div class="question">
+<p>Can I modify LLVM source code and redistribute the modified source?</p>
+</div>
+
+<div class="answer">
+<p>Yes. The modified source distribution must retain the copyright notice and
+follow the three bulletted conditions listed in the <a
+href="http://llvm.org/releases/1.3/LICENSE.TXT">LLVM license</a>.</p>
+</div>
+
+<div class="question">
+<p>Can I modify LLVM source code and redistribute binaries or other tools based
+on it, without redistributing the source?</p>
+</div>
+
+<div class="answer">
+<p>Yes, this is why we distribute LLVM under a less restrictive license than
+GPL, as explained in the first question above.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="source">Source Code</a>
+</div>
+<!-- *********************************************************************** -->
+
+<div class="question">
+<p>In what language is LLVM written?</p>
+</div>
+
+<div class="answer">
+<p>All of the LLVM tools and libraries are written in C++ with extensive use of
+the STL.</p>
+</div>
+
+<div class="question">
+<p>How portable is the LLVM source code?</p>
+</div>
+
+<div class="answer">
+<p>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>
+
+<p>Some porting problems may exist in the following areas:</p>
+
+<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.</li>
+
+ <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.</li>
+</ul>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="build">Build Problems</a>
+</div>
+<!-- *********************************************************************** -->
+
+<div class="question">
+<p>When I run configure, it finds the wrong C compiler.</p>
+</div>
+
+<div class="answer">
+
+<p>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.</p>
+
+<p>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>
+
+</div>
+
+<div class="question">
+<p>The <tt>configure</tt> script finds the right C compiler, but it uses the
+LLVM linker from a previous build. What do I do?</p>
+</div>
+
+<div class="answer">
+<p>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:</p>
+
+<ol>
+ <li><p>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>
+
+ <li><p>Run <tt>configure</tt> with an alternative <tt>PATH</tt> that is
+ correct. In a Borne compatible shell, the syntax would be:</p>
+
+<div class="doc_code">
+<pre>
+% PATH=[the path without the bad program] ./configure ...
+</pre>
+</div>
+
+ <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.</p></li>
+</ol>
+
+</div>
+
+<div class="question">
+<p>When creating a dynamic library, I get a strange GLIBC error.</p>
+</div>
+
+<div class="answer">
+<p>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>
+</div>
+
+<div class="question">
+<p>I've updated my source tree from Subversion, and now my build is trying to
+use a file/directory that doesn't exist.</p>
+</div>
+
+<div class="answer">
+<p>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>
+</div>
+
+<div class="question">
+<p>I've modified a Makefile in my source tree, but my build tree keeps using the
+old version. What do I do?</p>
+</div>
+
+<div class="answer">
+<p>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>
+
+<div class="doc_code">
+<pre>% ./config.status <relative path to Makefile></pre>
+</div>
+
+<p>If the Makefile is new, you will have to modify the configure script to copy
+it over.</p>
+
+</div>
+
+<div class="question">
+<p>I've upgraded to a new version of LLVM, and I get strange build errors.</p>
+</div>
+
+<div class="answer">
+
+<p>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>
+
+<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>
+
+</div>
+
+<div class="question">
+<p>I've built LLVM and am testing it, but the tests freeze.</p>
+</div>
+
+<div class="answer">
+
+<p>This is most likely occurring because you built a profile or release
+(optimized) build of LLVM and have not specified the same information on the
+<tt>gmake</tt> command line.</p>
+
+<p>For example, if you built LLVM with the command:</p>
+
+<div class="doc_code">
+<pre>% gmake ENABLE_PROFILING=1</pre>
+</div>
+
+<p>...then you must run the tests with the following commands:</p>
+
+<div class="doc_code">
+<pre>
+% cd llvm/test
+% gmake ENABLE_PROFILING=1
+</pre>
+</div>
+
+</div>
+
+<div class="question">
+<p>Why do test results differ when I perform different types of builds?</p>
+</div>
+
+<div class="answer">
+
+<p>The LLVM test suite is dependent upon several features of the LLVM tools and
+libraries.</p>
+
+<p>First, the debugging assertions in code are not enabled in optimized or
+profiling builds. Hence, tests that used to fail may pass.</p>
+
+<p>Second, some tests may rely upon debugging options or behavior that is only
+available in the debug build. These tests will fail in an optimized or profile
+build.</p>
+
+</div>
+
+<div class="question">
+<p>Compiling LLVM with GCC 3.3.2 fails, what should I do?</p>
+</div>
+
+<div class="answer">
+<p>This is <a href="http://gcc.gnu.org/PR?13392">a bug in GCC</a>, and
+affects projects other than LLVM. Try upgrading or downgrading your GCC.</p>
+</div>
+
+<div class="question">
+<p>After Subversion update, rebuilding gives the error "No rule to make
+target".</p>
+</div>
+
+<div class="answer">
+<p>If the error is of the form:</p>
+
+<div class="doc_code">
+<pre>
+gmake[2]: *** No rule to make target `/path/to/somefile', needed by
+`/path/to/another/file.d'.<br>
+Stop.
+</pre>
+</div>
+
+<p>This may occur anytime files are moved within the Subversion repository or
+removed entirely. In this case, the best solution is to erase all
+<tt>.d</tt> files, which list dependencies for source files, and rebuild:</p>
+
+<div class="doc_code">
+<pre>
+% cd $LLVM_OBJ_DIR
+% rm -f `find . -name \*\.d`
+% gmake
+</pre>
+</div>
+
+<p>In other cases, it may be necessary to run <tt>make clean</tt> before
+rebuilding.</p>
+</div>
+
+<div class="question"><p><a name="llvmc">
+The <tt>llvmc</tt> program gives me errors/doesn't work.</a></p>
+</div>
+
+<div class="answer">
+<p><tt>llvmc</tt> is experimental and isn't really supported. We suggest
+using <tt>llvm-gcc</tt> instead.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="felangs">Source Languages</a></div>
+
+<div class="question"><p>
+ <a name="langs">What source languages are supported?</a></p>
+</div>
+<div class="answer">
+ <p>LLVM currently has full support for C and C++ source languages. These are
+ available through a special version of GCC that LLVM calls the
+ <a href="#cfe">C Front End</a></p>
+ <p>There is an incomplete version of a Java front end available in the
+ <tt>java</tt> module. There is no documentation on this yet so
+ you'll need to download the code, compile it, and try it.</p>
+ <p>In the <tt>stacker</tt> module is a compiler and runtime
+ library for the Stacker language, a "toy" language loosely based on Forth.</p>
+ <p>The PyPy developers are working on integrating LLVM into the PyPy backend
+ so that PyPy language can translate to LLVM.</p>
+</div>
+<div class="question"><p><a name="langhlsupp">
+ What support is there for a higher level source language constructs for
+ building a compiler?</a></p>
+</div>
+<div class="answer">
+ <p>Currently, there isn't much. LLVM supports an intermediate representation
+ which is useful for code representation but will not support the high level
+ (abstract syntax tree) representation needed by most compilers. There are no
+ facilities for lexical nor semantic analysis. There is, however, a <i>mostly
+ implemented</i> configuration-driven
+ <a href="CompilerDriver.html">compiler driver</a> which simplifies the task
+ of running optimizations, linking, and executable generation.</p>
+</div>
+
+<div class="question"><p><a name="langhlsupp">
+ I don't understand the GetElementPtr instruction. Help!</a></p>
+</div>
+<div class="answer">
+ <p>See <a href="GetElementPtr.html">The Often Misunderstood GEP
+ Instruction</a>.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="cfe">Using the GCC Front End</a>
+</div>
+
+<div class="question">
+<p>
+When I compile software that uses a configure script, the configure script
+thinks my system has all of the header files and libraries it is testing for.
+How do I get configure to work correctly?
+</p>
+</div>
+
+<div class="answer">
+<p>
+The configure script is getting things wrong because the LLVM linker allows
+symbols to be undefined at link time (so that they can be resolved during JIT
+or translation to the C back end). That is why configure thinks your system
+"has everything."
+</p>
+<p>
+To work around this, perform the following steps:
+</p>
+<ol>
+ <li>Make sure the CC and CXX environment variables contains the full path to
+ the LLVM GCC front end.</li>
+
+ <li>Make sure that the regular C compiler is first in your PATH. </li>
+
+ <li>Add the string "-Wl,-native" to your CFLAGS environment variable.</li>
+</ol>
+
+<p>
+This will allow the <tt>llvm-ld</tt> linker to create a native code executable
+instead of shell script that runs the JIT. Creating native code requires
+standard linkage, which in turn will allow the configure script to find out if
+code is not linking on your system because the feature isn't available on your
+system.</p>
+</div>
+
+<div class="question">
+<p>
+When I compile code using the LLVM GCC front end, it complains that it cannot
+find libcrtend.a.
+</p>
+</div>
+
+<div class="answer">
+<p>
+The only way this can happen is if you haven't installed the runtime library. To
+correct this, do:</p>
+
+<div class="doc_code">
+<pre>
+% cd llvm/runtime
+% make clean ; make install-bytecode
+</pre>
+</div>
+</div>
+
+<div class="question">
+<p>
+How can I disable all optimizations when compiling code using the LLVM GCC front end?
+</p>
+</div>
+
+<div class="answer">
+<p>
+Passing "-Wa,-disable-opt -Wl,-disable-opt" will disable *all* cleanup and
+optimizations done at the llvm level, leaving you with the truly horrible
+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>
+
+<div class="doc_code">
+<pre>
+% llvm-g++ x.cpp -o program
+</pre>
+</div>
+
+ <p>or:</p>
+
+<div class="doc_code">
+<pre>
+% llvm-g++ a.cpp -c
+% llvm-g++ b.cpp -c
+% llvm-g++ a.o b.o -o program
+</pre>
+</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>
+
+ <li><p>Convert the LLVM code to C code, using the LLC tool with the C
+ backend:</p>
+
+<div class="doc_code">
+<pre>
+% llc -march=c program.bc -o program.c
+</pre>
+</div></li>
+
+<li><p>Finally, compile the C file:</p>
+
+<div class="doc_code">
+<pre>
+% cc x.c
+</pre>
+</div></li>
+
+</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>
+
+<p>Also note: this specific sequence of commands won't work if you use a
+function defined in the C++ runtime library (or any other C++ library). To
+access an external C++ library, you must manually compile libstdc++ to LLVM
+bitcode, statically link it into your program, then use the commands above to
+convert the whole result into C code. Alternatively, you can compile the
+libraries and your application into two different chunks of C code and link
+them.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="cfe_code">Questions about code generated by the GCC front-end</a>
+</div>
+
+<div class="question">
+<a name="iosinit"></a>
+<p> What is this <tt>llvm.global_ctors</tt> and
+<tt>_GLOBAL__I__tmp_webcompile...</tt> stuff that happens when I #include
+<iostream>?</p>
+</div>
+
+<div class="answer">
+
+<p>If you #include the <iostream> header into a C++ translation unit, the
+file will probably use the <tt>std::cin</tt>/<tt>std::cout</tt>/... global
+objects. However, C++ does not guarantee an order of initialization between
+static objects in different translation units, so if a static ctor/dtor in your
+.cpp file used <tt>std::cout</tt>, for example, the object would not necessarily
+be automatically initialized before your use.</p>
+
+<p>To make <tt>std::cout</tt> and friends work correctly in these scenarios, the
+STL that we use declares a static object that gets created in every translation
+unit that includes <tt><iostream></tt>. This object has a static
+constructor and destructor that initializes and destroys the global iostream
+objects before they could possibly be used in the file. The code that you see
+in the .ll file corresponds to the constructor and destructor registration code.
+</p>
+
+<p>If you would like to make it easier to <b>understand</b> the LLVM code
+generated by the compiler in the demo page, consider using <tt>printf()</tt>
+instead of <tt>iostream</tt>s to print values.</p>
+
+</div>
+
+<!--=========================================================================-->
+
+<div class="question"><p>
+<a name="codedce"></a>
+Where did all of my code go??
+</p></div>
+
+<div class="answer">
+<p>
+If you are using the LLVM demo page, you may often wonder what happened to all
+of the code that you typed in. Remember that the demo script is running the
+code through the LLVM optimizers, so if your code doesn't actually do anything
+useful, it might all be deleted.
+</p>
+
+<p>
+To prevent this, make sure that the code is actually needed. For example, if
+you are computing some expression, return the value from the function instead of
+leaving it in a local variable. If you really want to constrain the optimizer,
+you can read from and assign to <tt>volatile</tt> global variables.
+</p>
+</div>
+
+<!--=========================================================================-->
+
+<div class="question"><p>
+<a name="undef"></a>
+<p>What is this "<tt>undef</tt>" thing that shows up in my code?
+</p></div>
+
+<div class="answer">
+<p>
+<a href="LangRef.html#undef"><tt>undef</tt></a> is the LLVM way of representing
+a value that is not defined. You can get these if you do not initialize a
+variable before you use it. For example, the C function:</p>
+
+<div class="doc_code">
+<pre>
+int X() { int i; return i; }
+</pre>
+</div>
+
+<p>Is compiled to "<tt>ret i32 undef</tt>" because "<tt>i</tt>" never has
+a value specified for it.</p>
+</div>
+
+<!-- *********************************************************************** -->
-<!--=====================================================================-->
-<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>
-
- <dt><b>I've built LLVM and am testing it, but the tests freeze.</b>
- <dd>
- This is most likely occurring because you built a profile or release
- (optimized) build of LLVM and have not specified the same information on
- the <tt>gmake</tt> command line.
- <p>
- For example, if you built LLVM with the command:
- <p>
- <tt>gmake ENABLE_PROFILING=1</tt>
- <p>
- ...then you must run the tests with the following commands:
- <p>
- <tt>cd llvm/test<br>gmake ENABLE_PROFILING=1</tt>
- <p>
-
- <dt><b>Why do test results differ when I perform different types of
- builds?</b>
- <dd>
- The LLVM test suite is dependent upon several features of the LLVM tools
- and libraries.
- <p>
- First, the debugging assertions in code are not enabled in optimized or
- profiling builds. Hence, tests that used to fail may pass.
- <p>
- Second, some tests may rely upon debugging options or behavior that is
- only available in the debug build. These tests will fail in an optimized
- or profile build.
-</dl>
<hr>
+<address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
-<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
-<br>
+ <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date$
+</address>
</body>
</html>
projects / oota-llvm.git / blobdiff