arm-none-eabi-gcc 编译错误:error: address of explicit register variable 'r_page

qqrilxk

在移植l4ka:pistachio过程中，当编译user程序时，出现如下编译错误，望大侠指教，谢 谢。

编译语句如下：
arm-none-eabi-gcc -x c++ -I../../../user/include -I../.. -I../../../user/../contrib/include   -DARM_LITTLE_ENDIAN -nostdinc -g -O2 -Wall -Wshadow -Wconversion  -DARM_LITTLE_ENDIAN -fno-exceptions -c ../../../user/lib/io/arm-getc.cc -o arm-getc.o


出现如下错误，
../../../user/include/l4/arm/syscalls.h: In function 'L4_ThreadId_t L4_ExchangeRegisters(L4_ThreadId_t, L4_Word_t, L4_Word_t, L4_Word_t, L4_Word_t, L4_Word_t, L4_ThreadId_t, L4_Word_t*, L4_Word_t*, L4_Word_t*, L4_Word_t*, L4_Word_t*, L4_ThreadId_t*)':
../../../user/include/l4/arm/syscalls.h:128: error: address of explicit register variable 'r_pager' requested
../../../user/include/l4/arm/syscalls.h:130: error: address of explicit register variable 'r_dest' requested
../../../user/include/l4/arm/syscalls.h: In function 'L4_MsgTag_t L4_Ipc(L4_ThreadId_t, L4_ThreadId_t, L4_Word_t, L4_ThreadId_t*)':
../../../user/include/l4/arm/syscalls.h:253: error: address of explicit register variable 'r_dest' requested
../../../user/include/l4/arm/syscalls.h: In function 'L4_MsgTag_t L4_Lipc(L4_ThreadId_t, L4_ThreadId_t, L4_Word_t, L4_ThreadId_t*)':
../../../user/include/l4/arm/syscalls.h:309: error: address of explicit register variable 'r_dest' requested

出现错误的函数如下;
L4_INLINE L4_ThreadId_t L4_ExchangeRegisters (L4_ThreadId_t dest,
                                              L4_Word_t control,
                                              L4_Word_t sp,
                                              L4_Word_t ip,
                                              L4_Word_t flags,
                                              L4_Word_t UserDefHandle,
                                              L4_ThreadId_t pager,
                                              L4_Word_t *old_control,
                                              L4_Word_t *old_sp,
                                              L4_Word_t *old_ip,
                                              L4_Word_t *old_flags,
                                              L4_Word_t *old_UserDefHandle,
                                    L4_ThreadId_t *old_pager)
{
    register L4_ThreadId_t r_dest   asm ("r0") = dest;
    register L4_Word_t r_control    asm ("r1") = control;
    register L4_Word_t r_sp            asm ("r2") = sp;
    register L4_Word_t r_ip            asm ("r3") = ip;
    register L4_Word_t r_flags            asm ("r4") = flags;
    register L4_Word_t r_userhandle asm ("r5") = UserDefHandle;
    register L4_ThreadId_t r_pager  asm ("r6") = pager;
    register __L4_ExchangeRegisters_t r_syscall asm ("r12")
            = __L4_ExchangeRegisters;

    __asm__ __volatile (
        __L4_SYSCALL
    : "=r" (r_dest), "=r" (r_control), "=r" (r_sp), "=r" (r_ip),
      "=r" (r_flags), "=r" (r_userhandle), "=r" (r_pager), "=r" (r_syscall)
    : "r" (r_syscall), "r" (r_dest), "r" (r_control), "r" (r_sp),
      "r" (r_ip), "r" (r_flags), "r" (r_userhandle), "r" (r_pager)
    : "r7", "lr", __L4_ALWAYS_CLOBBER
    );

    *old_control = r_control;
    *old_sp = r_sp;
    *old_ip = r_ip;
    *old_flags = r_flags;
    *old_UserDefHandle = r_userhandle;
    *old_pager = r_pager;

    return r_dest;
}



不知这是什么错误，怎么解决？

EricFisher

../../../user/include/l4/arm/syscalls.h:128: error: address of explicit register variable 'r_pager' requested

这行的代码是什么？

这个错误的意思是，如果一个变量被显式的放在寄存器中，那么就不能对这个变量进行寻址操作了，否则报错。

这里摘抄一个gcc testsuite中的测试例子

1. void g(int *);
   
2. 
   
3. void f(void)
   
4. {
   
5.   register int x __asm ("eax");
   
6.   g(&x);        /* { dg-error "address of explicit register variable" } */
   
7. }
   

复制代码