PortsAndClang [FreeBSD WIKI]

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====== Ports and Clang ======

This page is for ports status with the clang compiler. Below you will find some common problems and solutions to some of these problems. Also a list of ports that are known not to work and need to be investigated, like KDE for example.

This is part of the [[BuildingFreeBSDWithClang|ClangBSD]] project.

**Contents**

===== Quickstart =====

In all supported %%FreeBSD%% releases, Clang is the default compiler on all architectures except mips*, powerpc*, and sparc64.  It is installed as cc, c++ and cpp.
To test building ports with clang on other archs, add the following lines to ''%%/etc/make.conf%%'':

<code>
CC=clang
CXX=clang++
CPP=clang-cpp
</code>

===== Build Failures =====

==== New Build failures from clang7 ====

Please see [[PortsAndClang/Clang7Regressions|Clang7Regressions]].

==== New Build failures from clang6 ====

Please see [[PortsAndClang/Clang6Regressions|Clang6Regressions]].

==== Notes on error classification ====

There is a script called [[http://svnweb.freebsd.org/base/projects/portbuild/scripts/processonelog|processonelog]] on the build cluster that attempts to [[http://portsmon.freebsd.org/errorlist.html|classify]] types of build errors.  It is just a sequence of **grep** invocations that we keep updated with the results of various build failures over the years.  You should not assume that its analysis is conclusive.

The errortypes created expressly for **clang** -exp runs:

  * [[http://portsmon.freebsd.org/errorlist.html#assumes_gcc|assumes_gcc]] (for code that fails to configure with clang because of hardwired assumptions about gcc)
  * [[http://portsmon.freebsd.org/errorlist.html#clang|clang]] (for code that fails to compile with clang)
  * [[http://portsmon.freebsd.org/errorlist.html#clang-bug|clang-bug]] (for bugs in the compiler itself, or code or invocation parameters it does not yet support)

Note the that following regressions might not be reported as **clang**, and instead as existing errors:

  * [[http://portsmon.freebsd.org/errorlist.html#bad_C++_code|bad C++ code]] (somewhat common)
  * [[http://portsmon.freebsd.org/errorlist.html#compiler_error|compiler error]] (somewhat common)
  * [[http://portsmon.freebsd.org/errorlist.html#configure_error|configure]] (somewhat less common)
  * [[http://portsmon.freebsd.org/errorlist.html#linker_error|linker error]] (quite common)

We know not all cases of **clang** will be caught by the script; the script needs to be optimized for performance reasons, and thus we cannot include all possible error cases.

Other notes:

  * You will see some errorlogs with reason [[http://portsmon.freebsd.org/errorlist.html#cluster|cluster]].  Often for package builds this is a transient error, as the explanation claims.  However, in some cases what is happening is that the configure step is spitting out **clang** errors having to do with unsupported options, and this makes the classifier script break.  The configure step of these ports needs to be fixed.

==== Older Build failures with fixes ====

^ Failure ^ Why ^ Solution ^
| undefined or duplicate symbols while linking | clang defaults to gnu99, while gcc defaults to gnu89. This causes problems with the inline and restrict keywords (and possibly others). inline does different things in gnu89/gnu99 | add "USE_CSTD=gnu89" to the port Makefile |
| Not respecting ${CC} and/or ${CXX} | Some ports have gcc/g++ hardcoded in their Makefiles. | CC ?= gcc, or reinplace line. |
| /usr/bin/nm: .foo.o: File format not recognized | clang produces llvm bitcode (used for LTO) when compiled with -O4. | Use -O3 or lower. |
| error: expected ';' at end of declaration, nested function definition | clang does not accept nested function definitions | Move the nested function to a static function at global scope. |

:idea: even if you add the **gnu89** stanza to the port Makefile, you still have to re-test your build with **gcc** because the build may break there.  In that case you may have to make the **gnu89** stanza conditional on compiler.

==== Build failures without fixes yet ====

^ Failure ^ Solution ^

| Assertion failed: (//something//) | If you know what you're doing, reduce a testcase and report clang/llvm bug upstream. Otherwise, just explain us how to reproduce it and we'll do it for you. |
| UNREACHABLE executed at //something// | ::: |
| Clang crashes | ::: |

==== Build failure false positives ====

Don't worry about these.  They are not your problem.

(TBA)

===== Runtime failures =====

Just because a port compiles, does not necessarily imply that it functions correctly:

(TBA)

===== If you're interested in helping =====

If you want to help with something mentioned (or not) below, join us on IRC and feel free to talk to us about it.

  * Reporting clang/llvm bugs upstream
  * Debugging miscompilations
  * Submitting ports PR with fixes

===== PRs =====

You may be able to save yourself some time by looking at the [[http://www.freebsd.org/cgi/query-pr-summary.cgi?category=ports&text=clang|current ports/ PRs mentioning clang]].  Some already have patches.

===== Obsolete versions of llvm/clang =====

  * Please see [[ObsoleteLLVMVersions]].

===== Contacts =====
  * irc://irc.oftc.net/#freebsd-clang
  * KoopMast

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{{tag>Ports Stale}}