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34 .Nd memory reallocation function
40 .Fn reallocarray "void *ptr" "size_t nmemb" "size_t size"
44 function is similar to the
51 and checks for integer overflow in the calculation
58 function returns a pointer to the allocated space; otherwise, a
60 pointer is returned and
67 when there is multiplication in the
73 For example, avoid this common idiom as it may lead to integer overflow:
74 .Bd -literal -offset indent
75 if ((p = malloc(num * size)) == NULL)
79 A drop-in replacement is the
83 .Bd -literal -offset indent
84 if ((p = reallocarray(NULL, num, size)) == NULL)
85 err(1, "reallocarray");
90 be careful to avoid the following idiom:
91 .Bd -literal -offset indent
93 if ((p = realloc(p, size)) == NULL)
97 Do not adjust the variable describing how much memory has been allocated
98 until the allocation has been successful.
99 This can cause aberrant program behavior if the incorrect size value is used.
100 In most cases, the above sample will also result in a leak of memory.
101 As stated earlier, a return value of
103 indicates that the old object still remains allocated.
104 Better code looks like this:
105 .Bd -literal -offset indent
107 if ((newp = realloc(p, newsize)) == NULL) {
119 it is important to ensure the new size value will not overflow;
120 i.e. avoid allocations like the following:
121 .Bd -literal -offset indent
122 if ((newp = realloc(p, num * size)) == NULL) {
128 .Bd -literal -offset indent
129 if ((newp = reallocarray(p, num, size)) == NULL) {
137 function first appeared in