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Haiku compilers

For legacy reason, Haiku uses gcc2 to build parts of the system. This only applies to the x86 32bit version of Haiku, which maintains binary compatibility with BeOS applications. The other ports of Haiku are not affected by this, and use a more modern version of GCC (version 10 at the time of the writing).

The compilers are available in the separate “buildtools” repository. This repository contains gcc as well as the binutils (assembler, linker, etc). These are modified versions of the GNU tools, to handle the specifics of Haiku. The gcc2 compiler is still getting some maintenance updates and bugfixes. For the modern tools, the goal is to eventually re-integrate these changes into the upstream version.

There is also work in progress to be able to build Haiku with llvm/clang as an alternative to gcc.

Summary of changes made to gcc for Haiku support

This is an incomplete list of the changes.

The -pthread option does nothing. In Haiku, pthreads are always enabled.

The -fPIE option does the same thing as -fPIC. In Haiku, executables are also loadable as shared libraries because they can be loaded using load_add_on for use as replicants. Using the standard gcc implementation of -fPIE would then break, because it generates code that can’t be used in a shared library. For this reason, -fPIE in Haiku instead does the same thing as -fPIC.

Header search path in Mac OS is case sensitive. Mac OS can handle both case sensitive and case insensitive filesystems. Building Haiku requires a case sensitive filesystem, otherwise it’s not possible to tell apart headers like string.h and String.h. When compiling gcc for Mac OS, it normally has code to force case insensitive comparison of header filenames, no matter what the underlying filesystem offers. This is disabled in our version of gcc.