gcc

USE flags

• ada - Build the ADA language (GNAT) frontend
• altivec - Add support for optimizations for G4 and G5/ppc970 processors
• awt - Useful only when building GCJ, this enables Abstract Window Toolkit (AWT) peer support on top of GTK+
• bootstrap - !!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used during original system bootstrapping [make stage2]
• build - !!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used for creating build images and the first half of bootstrapping [make stage1]
• cilk - Support the Cilk Plus language (C/C++ based languages for parallel programming)
• custom-cflags - Build with user-specified CFLAGS (unsupported)
• cxx - Build support for C++ (bindings, extra libraries, code generation, ...)
• d - Enable support for the D programming language
• debug - Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
• doc - Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
• elibc_FreeBSD - ELIBC setting for systems that use the FreeBSD C library
• examples - Install examples, usually source code
• fixed-point - Enable fixed-point arithmetic support for MIPS targets in gcc (Warning: significantly increases compile time!)
• fortran - Add support for fortran
• gcj - Build the GCJ Java language frontend.
• go - Build the GCC Go language frontend.
• graphite - Add support for the framework for loop optimizations based on a polyhedral intermediate representation
• hardened - Activate default security enhancements for toolchain (gcc, glibc, binutils)
• java - Add support for Java
• jit - Enable libgccjit so other applications can embed gcc for Just-In-Time compilation. This will slow down the compiler a bit as it forces all of the toolchain to be shared libs.
• libssp - Build SSP support into a dedicated library rather than use the code in the C library (DO NOT ENABLE THIS IF YOU DON'T KNOW WHAT IT DOES)
• lto - Build using Link Time Optimizations (LTO)
• mpx - Enable support for Intel Memory Protection Extensions (MPX)
• multilib - On 64bit systems, if you want to be able to compile 32bit and 64bit binaries
• nls - Add Native Language Support (using gettext - GNU locale utilities)
• nptl - Enable support for Native POSIX Threads Library, the new threading module (requires linux-2.6 or better usually)
• objc - Build support for the Objective C code language
• objc++ - Build support for the Objective C++ language
• objc-gc - Build support for the Objective C code language Garbage Collector
• openmp - Build support for the OpenMP (support parallel computing), requires >=sys-devel/gcc-4.2 built with USE="openmp"
• pch - Enable precompiled header support for faster compilation at the expense of disk space and memory (>=sys-devel/gcc-3.4 only)
• pgo - Build GCC using Profile Guided Optimization (PGO)
• pie - Build programs as Position Independent Executables (a security hardening technique)
• sanitize - Build support for various sanitizer functions (ASAN/TSAN/etc...)
• source - Zip the sources and install them
• ssp - Build packages with stack smashing protector on by default
• static - !!do not set this during bootstrap!! Causes binaries to be statically linked instead of dynamically
• systemtap - enable systemtap static probe points
• test - Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
• valgrind - Enable valgrind annotations for gcc internals (useful for gcc debugging).
• vanilla - Do not add extra patches which change default behaviour; DO NOT USE THIS ON A GLOBAL SCALE as the severity of the meaning changes drastically
• vtv - Build support for virtual table verification (a C++ hardening feature)
• zstd - Enable support for ZSTD compression