为想明白的函数指针

komany

int *max(int a,int b)
{                 if(a>b) return &a;
         else return &b;        
}
void main()
{        
int * p = max(40,50);
int * q = max(10,20);
  printf("%d \n",(*q) + (* p) );
printf("%d \n",(*max(79,89))+(*max(10,40)));
}

komany

1. push ebp
   
2. .text:00401091 mov ebp, esp
   
3. .text:00401093 sub esp, 44h
   
4. .text:00401096 push ebx
   
5. .text:00401097 push esi
   
6. .text:00401098 push edi
   
7. .text:00401099 push 32h ; b
   
8. .text:0040109B push 28h ; a
   
9. .text:0040109D call j__max
   
10. .text:004010A2 add esp, 8
    
11. .text:004010A5 mov [ebp+p], eax
    
12. .text:004010A8 push 46h ; b
    
13. .text:004010AA push 3Ch ; a
    
14. .text:004010AC call j__a1
    
15. .text:004010B1 add esp, 8
    
16. .text:004010B4 mov eax, [eax]
    
17. .text:004010B6 mov ecx, [ebp+p]
    
18. .text:004010B9 add eax, [ecx]
    
19. .text:004010BB push eax
    
20. .text:004010BC push offset format ; "%d \n"
    
21. .text:004010C1 call _printf
    
22. .text:004010C6 add esp, 8
    
23. .text:004010C9 pop edi
    
24. .text:004010CA pop esi
    
25. .text:004010CB pop ebx
    
26. .text:004010CC mov esp, ebp
    
27. .text:004010CE pop ebp
    
28. .text:004010CF retn
    
29. .text:004010CF _main endp
    
30. int *__cdecl j__a1(int a, int b)
    
31. .text:0040100F j__a1 proc near ; CODE XREF: _main+1Cp
    
32. .text:0040100F jmp _a1
    
33. .text:0040100F j__a1 endp
    
34. .text:0040100F
    
35. .text:0040100F ; ---------------------------------------------------------------------------
    
36. .text:00401014 db 1Ch dup(0CCh)
    
37. .text:00401030
    
38. .text:00401030 ; =============== S U B R O U T I N E =======================================
    
39. .text:00401030
    
40. .text:00401030 ; Attributes: bp-based frame
    
41. .text:00401030
    
42. .text:00401030 ; int *__cdecl max(int a, int b)
    
43. .text:00401030 _max proc near ; CODE XREF: j__maxj
    
44. .text:00401030
    
45. .text:00401030 a = dword ptr 8
    
46. .text:00401030 b = dword ptr 0Ch
    
47. .text:00401030
    
48. .text:00401030 push ebp
    
49. .text:00401031 mov ebp, esp
    
50. .text:00401033 sub esp, 40h
    
51. .text:00401036 push ebx
    
52. .text:00401037 push esi
    
53. .text:00401038 push edi
    
54. .text:00401039 mov eax, [ebp+a]
    
55. .text:0040103C cmp eax, [ebp+b]
    
56. .text:0040103F jle short loc_401046
    
57. .text:00401041 lea eax, [ebp+a]
    
58. .text:00401044 jmp short loc_401049
    
59. .text:00401046 ; ---------------------------------------------------------------------------
    
60. .text:00401046
    
61. .text:00401046 loc_401046: ; CODE XREF: _max+Fj
    
62. .text:00401046 lea eax, [ebp+b]
    
63. .text:00401049
    
64. .text:00401049 loc_401049: ; CODE XREF: _max+14j
    
65. .text:00401049 pop edi
    
66. .text:0040104A pop esi
    
67. .text:0040104B pop ebx
    
68. .text:0040104C mov esp, ebp
    
69. .text:0040104E pop ebp
    
70. .text:0040104F retn
    
71. .text:0040104F _max endp
    
72. .text:0040104F
    
73. .text:0040104F ; ---------------------------------------------------------------------------
    
74. .text:00401050 db 10h dup(0CCh)
    
75. .text:00401060
    
76. .text:00401060 ; =============== S U B R O U T I N E =======================================
    
77. .text:00401060
    
78. .text:00401060 ; Attributes: bp-based frame
    
79. .text:00401060
    
80. .text:00401060 ; int *__cdecl a1(int a, int b)
    
81. .text:00401060 _a1 proc near ; CODE XREF: j__a1j
    
82. .text:00401060
    
83. .text:00401060 a = dword ptr 8
    
84. .text:00401060 b = dword ptr 0Ch
    
85. .text:00401060
    
86. .text:00401060 push ebp
    
87. .text:00401061 mov ebp, esp
    
88. .text:00401063 sub esp, 40h
    
89. .text:00401066 push ebx
    
90. .text:00401067 push esi
    
91. .text:00401068 push edi
    
92. .text:00401069 mov eax, [ebp+a]
    
93. .text:0040106C cmp eax, [ebp+b]
    
94. .text:0040106F jle short loc_401076
    
95. .text:00401071 lea eax, [ebp+a]
    
96. .text:00401074 jmp short loc_401079
    
97. .text:00401076 ; ---------------------------------------------------------------------------
    
98. .text:00401076
    
99. .text:00401076 loc_401076: ; CODE XREF: _a1+Fj
    
100. .text:00401076 lea eax, [ebp+b]
     
101. .text:00401079
     
102. .text:00401079 loc_401079: ; CODE XREF: _a1+14j
     
103. .text:00401079 pop edi
     
104. .text:0040107A pop esi
     
105. .text:0040107B pop ebx
     
106. .text:0040107C mov esp, ebp
     
107. .text:0040107E pop ebp
     
108. .text:0040107F retn
     
109. .text:0040107F _a1 endp
     

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komany

想明白了，结贴/:12

liuxianfu

看了有收获

yhtjay

/:L 给点中文……新手更明白……