apple-gcc42 failed to compile: conflicting types for 'psignal'

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I was trying to install mkvutoolnix but the installation stopped when compiling apple-gcc42. I'm on a core i7 macbook air (2011) with Lion.

$ uname -a Darwin MacBook-Air.local 11.2.0 Darwin Kernel Version 11.2.0: Tue Aug 9 20:54:00 PDT 2011; root:xnu-1699.24.8~1/RELEASE_X86_64 x86_64

$ xcodebuild -version Xcode 4.2 Build version 4D199

I'm attaching the complete log file, here's the first error I see:

info:build /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_apple-gcc42/apple-gcc42/work/objroot/src/libiberty/strsignal.c:552:1: error: conflicting types for 'psignal' :info:build psignal (unsigned signo, char *message) :info:build ^{:info:build /usr/include/signal.h:105:6: note: previous declaration is here :info:build void psignal(unsigned int, const char *); :info:build} :info:build /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_apple-gcc42/apple-gcc42/work/objroot/src/libiberty/strsignal.c:558:30: warning: comparison of integers of different signs: 'unsigned int' and 'int' [-Wsign-compare]

:info:build if ((signo <= 0)

(signo >= sys_nsig))

:info:build ~ ^{:info:build 1 warning and 1 error generated. :info:build make[4]: * [strsignal.o] Error 1 :info:build make[4]: * Waiting for unfinished jobs.... :info:build make[5]: Nothing to be done for `all'. :info:build make[3]: * [all-stage1-libiberty] Error 2 :info:build make[2]: * [stage1-bubble] Error 2 :info:build make[1]: * [all] Error 2 :info:build + exit 1 :info:build make: * [install] Error 1 :info:build make: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_apple-gcc42/apple-gcc42/work/gcc-5666.3'}