1.9.1 preview 1 does not build on mac OSX 10.5.5
I downloaded the tarball from uby-lang.org, untarred and ran ./configure, which succeeded.
I am of the opinion that things should 'work out of the box' on each platform, with just ./configure, make, and sudo make install required to build and install.
Running make reveals problems with readline.c :
gcc -I. -I../../.ext/include/i386-darwin9.5.0 -I../.././include -I../.././ext/readline -DRUBY_EXTCONF_H="extconf.h" -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common -O2 -g -Wall -Wno-parentheses -pipe -fno-common -o readline.o -c readline.c
readline.c: In function ‘filename_completion_proc_call’:
readline.c:1131: warning: implicit declaration of function ‘completion_matches’
readline.c:1132: error: ‘filename_completion_function’ undeclared (first use in this function)
readline.c:1132: error: (Each undeclared identifier is reported only once
readline.c:1132: error: for each function it appears in.)
readline.c:1132: warning: assignment makes pointer from integer without a cast
readline.c: In function ‘username_completion_proc_call’:
readline.c:1157: error: ‘username_completion_function’ undeclared (first use in this function)
readline.c:1157: warning: assignment makes pointer from integer without a cast
make: *** [readline.o] Error 1
make: *** [exts] Error 1