Packages with the clang use flag

app-doc / doxygen : Documentation system for most programming languages

support for sys-devel/clang assisted parsing

app-forensics / honggfuzz : A general purpose fuzzer with feedback support

Enable clang support (pull sys-libs/blocksruntime dependency).

app-office / libreoffice : A full office productivity suite

Use Clang compiler instead of GCC

dev-lang / moarvm : A 6model-based VM for NQP and Raku

Use clang compiler instead of GCC

dev-lang / nqp : Not Quite Perl, a Raku bootstrapping compiler

Toggle usage of the clang compiler in conjunction with MoarVM

dev-lang / rakudo : A compiler for the Raku programming language

Use Clang to compile the MoarVM backend

dev-lang / spidermonkey : SpiderMonkey is Mozilla's JavaScript engine written in C and C++

Use Clang compiler instead of GCC

dev-qt / qt-creator : Lightweight IDE for C++/QML development centering around Qt

Build clang-based plugins for C/C++ development (code model, formatting, static analysis)

dev-util / edi : An EFL-based IDE

Provide integration with sys-devel/clang and dev-util/bear for autocompletion, inline errors and information about compilation units.

dev-util / gnome-builder : An IDE for writing GNOME-based software

Provide integration with sys-devel/clang for best possible C/C++ autocompletion, semantic highlighting, symbol resolving, and diagnostics support

dev-util / hfstospell : HFST spell checker library and command line tool

Use different logic in ebuild when clang is used

dev-util / perf : Userland tools for Linux Performance Counters

Enable builtin clang and LLVM support

mail-client / thunderbird : Thunderbird Mail Client

Use Clang compiler instead of GCC

net-misc / zerotier : A software-based managed Ethernet switch for planet Earth

Use Clang compiler instead of GCC

sys-libs / compiler-rt : Compiler runtime library for clang (built-in part)

Force building using installed clang (rather than the default CC/CXX).

sys-libs / compiler-rt-sanitizers : Compiler runtime libraries for clang (sanitizers & xray)

Force building using installed clang (rather than the default CC/CXX).

www-client / firefox : Firefox Web Browser

Use Clang compiler instead of GCC