I found something that causes a fatal GCC bug with both the stock
GCC, and gcc-2.8.1 built from ports.  Here's how it aborts:

  cc -c -O -pipe -DFREEBSD_ELF     -I. -I. -I./config -DHAVE_CONFIG_H \
   -I./../include/opcode -I./../readline  -I../bfd -I./../bfd  -I./../include \
   ada-lang.c
  ada-lang.c: In function `ada_evaluate_subexp':
  ada-lang.c:5951: internal error--insn does not satisfy its constraints:
  (insn 2997 2996 4542 (parallel[ 
              (set (reg:DI 1 %edx)
                  (minus:DI (reg:DI 0 %eax)
                      (reg/v:DI 3 %ebx)))
              (clobber (scratch:SI))
          ] ) 135 {subdi3} (insn_list 2982 (insn_list 2994 (nil)))
      (expr_list:REG_DEAD (mem:DI (plus:SI (reg:SI 6 %ebp)
                  (const_int -64)))
          (expr_list:REG_DEAD (reg/v:DI 3 %ebx)
              (expr_list:REG_UNUSED (scratch:SI)
                  (nil)))))
  cc: Internal compiler error: program cc1 got fatal signal 6
  *** Error code 1

Fix: 

I don't know how to fix GCC, but a work-around to the bug can
be made by changing 2 ocurrences of the following line:

      (*pos) += 3 + BYTES_TO_EXP_ELEM (tem + 1);

in ada-lang.c to

      (*pos) = (*pos) + 3 + BYTES_TO_EXP_ELEM (tem + 1);
How-To-Repeat: This can be reproduced by building the Ada-aware GDB port found at:

  ftp://ftp.pcnet.com/users/eischen/FreeBSD/adagdb-4.17-port.tar.gz

and building with 'make EXPOSE_FATAL_GCC_ERROR=yes'.  If you
don't define EXPOSE_FATAL_GCC_ERROR, a work-around patch is
applied and the port successfully builds.