Backtrace:
In ice-9/boot-9.scm:
  1752:10 15 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          14 (apply-smob/0 #<thunk 7f8c263e4300>)
In ice-9/boot-9.scm:
    724:2 13 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8 12 (_ #(#(#<directory (guile-user) 7f8c263e7c80>)))
In mescc/mescc.scm:
   123:16 11 (mescc:assemble ((kernel . "linux") (arch . "x86_64") ?))
In srfi/srfi-1.scm:
   586:17 10 (map1 ("crt1.c"))
In ice-9/ports.scm:
   433:17  9 (call-with-input-file _ _ #:binary _ #:encoding _ # _)
    472:4  8 (_ _)
In mescc/compile.scm:
    64:14  7 (c99-ast->info #<<info> types: (("char" . #<<type> typ?> ?)
In srfi/srfi-1.scm:
   460:18  6 (fold #<procedure ast->info (o info)> _ _)
In mescc/compile.scm:
  2688:17  5 (fctn-defn->info ((decl-spec-list (type-spec (?))) # #) #)
  1729:20  4 (fk)
In srfi/srfi-1.scm:
   460:18  3 (fold #<procedure ast->info (o info)> #<<info> types: ?> ?)
In mescc/compile.scm:
  1939:20  2 (fk)
    899:6  1 (expr->register (asm-expr (@ (extension "GNUC")) (# ?)) #)
  1450:11  0 (fk)

mescc/compile.scm:1450:11: In procedure fk:
expr->register: not supported:  (asm-expr (@ (extension "GNUC")) (string "mov____%rbp,%rax"))
make: *** [GNUmakefile:99：build] Error 1