c++ - 函数调用时入栈参数与局部变量在栈中地址问题

Question

{代码...} 输出：gcc 4.9.2 -32bit release:Address of a: 0x6efea0Address of b: 0x6efea4Address of c: 0x6efea8Address of d: 0x6efeacAddress of e: 0x6efe8c而就我目前的知识了解，栈是从高地址到底地址存储...

阿神 · Answer

LZ, you’d better put a piece of your assembly code and just add -S when compiling.
I ran your code and my output is as follows:

Address of a: 0x7fff3e06b44c
Address of b: 0x7fff3e06b448
Address of c: 0x7fff3e06b444
Address of d: 0x7fff3e06b440
Address of e: 0x7fff3e06b45c
Address of f: 0x7fff3e06b458

The difference between e and a is 0x10, which is 16 in decimal.

I used your code to generate a piece of assembly, and found that the parameters of foo() were not pushed onto the stack. Instead, the parameters were given to register first, and then the register value was stored in the stack, so it is similar to your situation. Different, you can see that the address of a is higher than that of d, and the addresses of these parameters are smaller than the local variables.

.globl main
    .type    main, @function
main:
.LFB958:
    .cfi_startproc
    .cfi_personality 0x3,__gxx_personality_v0
    pushq    %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset 6, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register 6
    movl    , %ecx
    movl    , %edx
    movl    , %esi
    movl    , %edi
    call    _Z3fooiiii
    movl    .LC0:
    .string    "Address of a: "
.LC1:
    .string    "Address of b: "
.LC2:
    .string    "Address of c: "
.LC3:
    .string    "Address of d: "
.LC4:
    .string    "Address of e: "
.LC5:
    .string    "Address of f: "
    .text
.globl _Z3fooiiii
    .type    _Z3fooiiii, @function
_Z3fooiiii:
.LFB957:
    .cfi_startproc
    .cfi_personality 0x3,__gxx_personality_v0
    pushq    %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset 6, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register 6
    subq    , %rsp
    movl    %edi, -20(%rbp)
    movl    %esi, -24(%rbp)
    movl    %edx, -28(%rbp)
    movl    %ecx, -32(%rbp)
    movl    $_ZSt3hexRSt8ios_base, %esi
    movl    $_ZSt4cout, %edi
    call    _ZNSolsEPFRSt8ios_baseS0_E
    movl    $.LC0, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -20(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    $.LC1, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -24(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    $.LC2, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -28(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    $.LC3, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -32(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    $.LC4, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -4(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    $.LC5, %esi
    movl    $_ZSt4cout, %edi
    call    _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
    leaq    -8(%rbp), %rdx
    movq    %rdx, %rsi
    movq    %rax, %rdi
    call    _ZNSolsEPKv
    movl    $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, %esi
    movq    %rax, %rdi
    call    _ZNSolsEPFRSoS_E
    movl    -20(%rbp), %edx
    movl    -24(%rbp), %eax
    addl    %eax, %edx
    movl    -28(%rbp), %eax
    addl    %eax, %edx
    movl    -32(%rbp), %eax
    leal    (%rdx,%rax), %eax
    leave
    .cfi_def_cfa 7, 8
    ret
    .cfi_endproc
, %eax
    leave
    .cfi_def_cfa 7, 8
    ret
    .cfi_endproc

rrreee

迷茫 · Answer

This problem is related to the platform, the calling convention adopted, and the compiler.
i386 platform, under the default _cdecl calling convention, on the runtime stack, between function parameters and function local variables are 1: return address (pc after call instruction), 2: caller’s stack frame base address ( ebp), 3: callee save registers (the number is different on different platforms), 4: information added to the stack in order to handle exceptions (different compilers may implement different things, gcc will add things)