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This noncompliant code example converts the string token stored in the static array buff to a signed integer value using the atoi() function.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
int si;
if (argc > 1) {
si = atoi(argv[1]);
}
|
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Unfortunately, atoi() and related functions lack a mechanism for reporting errors for invalid values. Specifically, the atoi(), atol(), and atoll() functions
- do Do not need to set
errnoon an error. - have Have undefined behavior if the value of the result cannot be represented. (See undefined behavior 119 of Annex J of the C Standard.)
- return Return 0 if the string does not represent an integer (which is indistinguishable from a correctly formatted, zero-denoting input string), but the C Standard only specifies the behavior of these functions on success.
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This compliant solution uses strtol() to convert a string token to an integer and ensures that the value is in the range of int.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
long sl;
int si;
char *end_ptr;
if (argc > 1) {
errno = 0;
sl = strtol(argv[1], &end_ptr, 10);
if ((sl == LONG_MIN || sl == LONG_MAX)
&& errno != 0)
{
perror("strtol error");
}
else if (end_ptr == argv[1]) {
if (puts("error encountered during conversion") == EOF) {
/* Handle Error */
}
}
else if (sl > INT_MAX) {
printf("%ld too large!\n", sl);
}
else if (sl < INT_MIN) {
printf("%ld too small!\n", sl);
}
else if ('\0' != *end_ptr) {
if (puts("extra characters on input line\n") == EOF) {
/* Handle Error */
}
}
else {
si = (int)sl;
}
}
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This noncompliant code example sets the file position indicator of an input stream back to the beginning using rewind().:
| Code Block | ||||
|---|---|---|---|---|
| ||||
char *file_name;
FILE *fp;
/* Initialize file_name */
fp = fopen(file_name, "r");
if (fp == NULL) {
/* Handle open error */
}
/* Read data */
rewind(fp);
/* Continue */
|
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This compliant solution uses fseek() instead of rewind() and checks to see if the operation succeeded.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
char *file_name;
FILE *fp;
/* Initialize file_name */
fp = fopen(file_name, "r");
if (fp == NULL) {
/* Handle open error */
}
/* Read data */
if (fseek(fp, 0L, SEEK_SET) != 0) {
/* Handle repositioning error */
}
/* Continue */
|
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This noncompliant code example calls setbuf() with a buf argument of NULL.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
FILE *file; /* Setup file */ setbuf(file, NULL); /* ... */ |
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This compliant solution calls setvbuf(), which returns nonzero if the operation failed.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
FILE *file;
char *buf = NULL;
/* Setup file */
if (setvbuf(file, buf, buf ? _IOFBF : _IONBF, BUFSIZ) != 0) {
/* Handle error */
}
/* ... */
|
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| [Klein 2002] | "Bullet Proof Integer Input Using strtol() |
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