Bus error from b64f08784cc50861dec80c26fce715982c02c9e9

[ksss]

compile warnings from macOS & clang.

CC    src/vm.c -> build/test/src/vm.o
/Users/ksss/src/github.com/ksss/mruby/src/vm.c:1210:11: warning: variable 'ci' is uninitialized when used here [-Wuninitialized]
          ci->nregs = bidx+1;
          ^~
/Users/ksss/src/github.com/ksss/mruby/src/vm.c:1192:23: note: initialize the variable 'ci' to silence this warning
      mrb_callinfo *ci;
                      ^
                       = NULL
1 warning generated.

$ mruby -e 'a(&1)'
[1]    79295 bus error  ./build/host/bin/mruby -e 'a(&1)'

[ksss]

Maybe from here b64f087