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A similar situation arises when realloc() is supplied a pointer to non-dynamically nondynamically allocated memory. The realloc() function is used to resize a block of dynamic memory. If realloc() is supplied a pointer to memory not allocated by a memory allocation function, such as malloc(), the program may terminate abnormally.
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| Code Block | ||
|---|---|---|
| ||
enum { MAX_ALLOCATION = 1000 };
int main(int argc, const char *argv[]) {
char *str = NULL;
size_t len;
if (argc == 2) {
len = strlen(argv[1])+1;
if (len > MAX_ALLOCATION) {
/* Handle Errorerror */
}
str = (char *)malloc(len);
if (str == NULL) {
/* Handle Allocationallocation Errorerror */
}
strcpy(str, argv[1]);
}
else {
str = "usage: $>a.exe [string]";
printf("%s\n", str);
}
/* ... */
free(str);
return 0;
}
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In the compliant solution, the program has been modified to eliminate the possibility of str referencing non-dynamic nondynamic memory when it is supplied to free().
| Code Block | ||
|---|---|---|
| ||
enum { MAX_ALLOCATION = 1000 };
int main(int argc, const char *argv[]) {
char *str = NULL;
size_t len;
if (argc == 2) {
len = strlen(argv[1])+1;
if (len > MAX_ALLOCATION) {
/* Handle Errorerror */
}
str = (char *)malloc(len);
if (str == NULL) {
/* Handle Allocationallocation Errorerror */
}
strcpy(str, argv[1]);
}
else {
printf("%s\n", "usage: $>a.exe [string]");
return -1;
}
/* ... */
free(str);
return 0;
}
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