The problem of function return value in C language

C language in the function of the return value of the problem, in the function of the local variables are mainly on the stack open, out of the function variable is recycled, for the function return is worth the problem, give the following a few more specific examples to illustrate:

2. function return value is a local variable defined in the function

   This type of return value can be used in the main function, because it is worthwhile to return a local variable, it is worth a copy, and in the main function we need only this value, so it is possible, for example

   
   

4. int fun (char *arr)

6. {

8. int num = 0;

10. while (*arr! = ' \\0 ')

12. {

14. num = num * + *arr-' 0 ';

18. arr++;

20. }

22. return num;

24. printf ("%d", num);

26. }

28. int main ()

30. {

32. int tem = 0;

34. Char *arr = "12345";

36. tem = Fun (arr);

38. printf ("%d", tem);

40. System ("pause");

42. return 0;

44. }

46. 2. The function returns the pointer variable defined in the function

48. Char *fun ()

50. {

54. Char *arr = "1234";

56. return arr;

58. }

60. int main ()

62. {

64. Char *tem = fun ();

66. printf ("%s", tem);

68. System ("pause");

70. return 0;

72. }

74. This is also true in the process of operation.

76. 3. Function cannot return the address of a local variable

80. int *fun ()

82. {

84. int a = 10;

86. Return &a;

88. }

90. int main ()

92. {

94. int *tem = Fun ();

96. printf ("%d", *tem);

98. System ("pause");

100. return 0;

102. }

104. 4. Function also cannot return the first address of an array

106. int *fun ()

108. {

110. int arr[] = {1, 2, 3, 4};

112. return arr;

114. }

116. int main ()

118. {

120. int *tem = Fun ();

122. System ("pause");

124. return 0;

126. }

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The problem of function return value in C language