Build issues on macOS - Githubissues

The PR is a one-line change, but there are really several apparent issues here. I'm only glancingly familiar with the internal details of autoconf and Homebrew, so I hesitate to suggest a specific fix. But let me see if I can describe the problems in sufficient detail that someone more familiar with these tools might know the proper update.

The top-level issue is that as of the current beta of macOS High Sierra (10.13.5, build 17F45c, with Xcode 9.3) --- and possibly for a while --- /usr/include/ucontext.h explicitly checks to see if the preprocessor symbol _XOPEN_SOURCE is defined, and if it is not, it aborts with the message "The deprecated ucontext routines require _XOPEN_SOURCE to be defined." riofs doesn't include this header directly, but it's being pulled in by something else. So currently, if you just use the recommended installation method of

brew install https://raw.github.com/skoobe/riofs/master/riofs.rb

the compilation aborts midway through.

Defining this symbol lets the compilation proceed, and riofs seems to work fine. This PR adds it to the Homebrew control file, but perhaps there's somewhere else in the configuration that it could go so as to cover non-Homebrew builds.

_XOPEN_SOURCE is some kind of POSIX compatibility flag, and it's supposed to have a value, as described here. Unfortunately, values of 700L, 600L, and 500L all produce catastrophic compilation meltdowns because of stuff that goes on in /usr/include/sys/cdefs.h. Just defining it without a value seems to be sufficient to sneak by the ucontext.h police without causing problems.

I also found that if you try to build riofs outside of Homebrew, the build system aborts because it can't confirm that libcrypto is installed. In macOS, this library is part of the base system. Homebrew provides a synthetic pkg-config receipt for it (on my system, /usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig/10.5/libcrypto.pc) and is able to set up the environment so that pkg-config finds it.

However, when you run the build through ./configure directly, you have to provide an explicit PKG_CONFIG_DIR=/usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig/10.5 argument to fix this problem. Unfortunately, you can't include that same argument in the riofs.rb file since it seems to screw up other autoconfiguration that Homebrew is already doing. The build then finds libcrypto but not glibc.

Perhaps the right solution is just to take this PR as-is and to clarify that riofs must only be installed through Homebrew; manual compilation isn't supported.

skoobe / riofs

Build issues on macOS #155