Question

是这个代码PIC（位置独立）？只要我知道PIC代码中一定没有库函数，但我不确定printf在这里被认为是库函数。

同样，在执行此代码后，edx寄存器中的值是多少？它是to_printf或printf的绝对地址，还是to_printf和next_i的地址差异？

to_printf: dd printf
get_my_loc:
call next_i
next_i: 
pop edx
ret
call get_my_loc
push edx
add edx, (to_print - next_i)

Answer 1

绝对地址，与第一次遇到子程序next_i时标签next_i的地址相同。之后，＆＃34;推edx＆＃34;执行时，edx仍然包含指令地址＆＃34; pop edx＆＃34;

sequence of execution   effect
---------------------------------------------------------------------------------------------------------------------
call get_my_loc                addr of next instruction (push edx) stacked. call it "addr1"     
call next_i                          addr of next instruction (pop edx) stacked.  "addr2"
pop edx                             addr2 -> edx
ret                                      continues at addr1. addr2 was popped already.
; next operations work on edx, containing addr2, pointing to "pop edx"             
push edx    
add edx, ...

在pic代码中使用库函数

1 个答案: