Starting with version 4.4, the FSF the licenses the GCC run-time library with a special exception:
| Under Section 7 of GPL version 3, you are granted additional | permissions described in the GCC Runtime Library Exception, version | 3.1, as published by the Free Software Foundation. The exception is reproduced below. Code covered by the exception includes routines in gcc/libgcc2.c, which are linked statically with many GCC-compiled programs, providing functionality like 64/64 -> 64 bit division for 32 bit architectures. (It's not just the C++ unwinder, as I originally thought.) At least with a strict interpretation, the run-time exception suffers from a significant issue with compilers which are not licensed under a GPLv3-compatible license (such as the GPLv2, or the QPL), and which are implemented in the language itself. (One such compiler is Objective Caml.) After compilation with GCC 4.4, such a compiler is a "work based on GCC" because it links to the GCC run-time library. Therefore, it's output cannot use the run-time library exception (it's not the result of an Eligible Compilation Process because it's neither the result of running "GCC, alone or with other GPL-compatible software," nor "it is done without using any work based on GCC"), and the resulting binary is covered by the GPLv3 (potentially among other licenses). Bootstrapping the compiler results in a non-redistributable binary if the compiler is not licensed under a GPLv3-compatible license (such as the QPL, in the Objective Caml example). We might weasel out of this if we always bootstrap off GCC 4.3, but this is not how the Objective Caml build system works (it bootstraps the compiler off pre-compiled bytecode shipped along the sources). Perhaps the above interpretation is too narrow, but I don't think it's a fringe reading. The FSF obviously wants to outlaw proprietary compilers, and from a purely license-centric point of view, a proprietary compiler is as good or bad as one licensed in a way which is not compatible with the GPLv3. What makes the license interpretation some awkward is the bootstrapping process and its recursive nature. I've asked the FSF for a clarification (the second time, the first clarification resulted in the Java bytecode exception). Until we know for sure how to interpret the exception, it's probably best not to make GCC 4.4 the default compiler in sid/squeeze. GCC RUNTIME LIBRARY EXCEPTION Version 3.1, 31 March 2009 Copyright (C) 2009 Free Software Foundation, Inc. <http://fsf.org/> Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. This GCC Runtime Library Exception ("Exception") is an additional permission under section 7 of the GNU General Public License, version 3 ("GPLv3"). It applies to a given file (the "Runtime Library") that bears a notice placed by the copyright holder of the file stating that the file is governed by GPLv3 along with this Exception. When you use GCC to compile a program, GCC may combine portions of certain GCC header files and runtime libraries with the compiled program. The purpose of this Exception is to allow compilation of non-GPL (including proprietary) programs to use, in this way, the header files and runtime libraries covered by this Exception. 0. Definitions. A file is an "Independent Module" if it either requires the Runtime Library for execution after a Compilation Process, or makes use of an interface provided by the Runtime Library, but is not otherwise based on the Runtime Library. "GCC" means a version of the GNU Compiler Collection, with or without modifications, governed by version 3 (or a specified later version) of the GNU General Public License (GPL) with the option of using any subsequent versions published by the FSF. "GPL-compatible Software" is software whose conditions of propagation, modification and use would permit combination with GCC in accord with the license of GCC. "Target Code" refers to output from any compiler for a real or virtual target processor architecture, in executable form or suitable for input to an assembler, loader, linker and/or execution phase. Notwithstanding that, Target Code does not include data in any format that is used as a compiler intermediate representation, or used for producing a compiler intermediate representation. The "Compilation Process" transforms code entirely represented in non-intermediate languages designed for human-written code, and/or in Java Virtual Machine byte code, into Target Code. Thus, for example, use of source code generators and preprocessors need not be considered part of the Compilation Process, since the Compilation Process can be understood as starting with the output of the generators or preprocessors. A Compilation Process is "Eligible" if it is done using GCC, alone or with other GPL-compatible software, or if it is done without using any work based on GCC. For example, using non-GPL-compatible Software to optimize any GCC intermediate representations would not qualify as an Eligible Compilation Process. 1. Grant of Additional Permission. You have permission to propagate a work of Target Code formed by combining the Runtime Library with Independent Modules, even if such propagation would otherwise violate the terms of GPLv3, provided that all Target Code was generated by Eligible Compilation Processes. You may then convey such a combination under terms of your choice, consistent with the licensing of the Independent Modules. 2. No Weakening of GCC Copyleft. The availability of this Exception does not imply any general presumption that third-party software is unaffected by the copyleft requirements of the license of GCC. -- To UNSUBSCRIBE, email to debian-legal-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
