On Sun, Jan 19, 2014 at 9:14 PM, Stephen J. Turnbull wrote: > > He has no objection to clang (or LLVM) itself, because it *is* free > software. However, the GNU Project sets higher standards, and Emacs > (and GCC) try to conform to them. Specifically, *defending* freedom, > including *shutting the door* on cooperation with non-free software: > > Do you mean, [gcc-xml outputs] the entire parse tree in full > detail? > Would it be conceivable to feed this into a nonfree back-end? > Would this mean that nonfree backends could take advantage > of our free front-ends? > That cat already seems to be out of the bag: http://dragonegg.llvm.org/ If so, it is very dangerous -- it would open the door to a > terrible setback for our defense of users' freedom. Namely, the > use of free software as part of compilers that are partly nonfree. > I don't remember, but I would guess that is why we have refused to > merge it into GCC. > > LLVM and Clang open the door to the same terrible setback. Since > they are not copylefted, their front-ends can be used with nonfree > back-ends and vice versa. [from the cited thread] > > So his objection is to emission of information that could be > conveniently used by non-free software to integrate free software into > a non-free toolchain. AIUI, this is basically the same configuration > that led to the confrontation with Steve Jobs over Objective-C, except > that if the output of the compiler front-end is part of the spec, you > would have almost no leverage in court to claim that it's a single > Work which is a derivative of the copyleft front-end. > RMS may have an inflated sense of the extent to which the greater compiler community (those developing and those using compilers) value gcc over clang / llvm. For many reason the latter is winning the day. Speed, memory footprint, modularity, ease of entry, size of development community all favor clang / llvm. Anecdotal evidence: my startup (Gnu / Linux based product) has just switched from gcc to clang. /john