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How should I verify that an integer value passed in from argv won't overflow?
The Next CEO of Stack OverflowWhy is there no strtoi in stdlib.h?How to detect unsigned integer multiply overflow?Write a program that sums the sequence of integers, as well as the smallest in the sequenceImprove INSERT-per-second performance of SQLite?Speed comparison with Project Euler: C vs Python vs Erlang vs HaskellC Programming: How to read input byte at a time and output only integers as tokens?How to avoid overflow error when finding LCM for series of large integersDoes the implementation of strtoul in glibc conflicts with the C11 standard?How do I re enter an integer value in a 'while' loop?C - Can't read user integer inputHow I can handle integer overflow?
I have a program that requires the user to enter an integer as a command line argument, in the form of ./program 100.
Obviously this will read the value in as a string, so I need to parse it to an integer. I have to ensure that the input value won't overflow an integer variable. I have read about strtol(), but it works with long variables and I have to stick with a regular int.
Is there anything similar that can be used for an int?
c
asked 4 hours ago
JakeJake
109212
|
show 10 more comments
I have a program that requires the user to enter an integer as a command line argument, in the form of ./program 100.
Obviously this will read the value in as a string, so I need to parse it to an integer. I have to ensure that the input value won't overflow an integer variable. I have read about strtol(), but it works with long variables and I have to stick with a regular int.
Is there anything similar that can be used for an int?
c
asked 4 hours ago
JakeJake
109212
7
Usestrtoland compare to INT_MAX/MIN.
– Eugene Sh.
4 hours ago
2
if (longvalue > INT_MAX) /* overflow */;don't forget to#include <limits.h>
– pmg
4 hours ago
1
@pmg check would fail for platforms whensizeof(int) == sizeof(long) = true.
– SergeyA
4 hours ago
1
@pmg, you can do it in a single check by just comparing for>= INT_MAX. This will always work.
– SergeyA
4 hours ago
1
@SergeyA Yeah, apparently one should handlestrtolerrors too. I assumed OP is already aware of that when mentioned usingstrtol.
– Eugene Sh.
4 hours ago
|
show 10 more comments
I have a program that requires the user to enter an integer as a command line argument, in the form of ./program 100.
Obviously this will read the value in as a string, so I need to parse it to an integer. I have to ensure that the input value won't overflow an integer variable. I have read about strtol(), but it works with long variables and I have to stick with a regular int.
Is there anything similar that can be used for an int?
c
asked 4 hours ago
JakeJake
109212
I have a program that requires the user to enter an integer as a command line argument, in the form of ./program 100.
Obviously this will read the value in as a string, so I need to parse it to an integer. I have to ensure that the input value won't overflow an integer variable. I have read about strtol(), but it works with long variables and I have to stick with a regular int.
Is there anything similar that can be used for an int?
c
c
asked 4 hours ago
JakeJake
109212
asked 4 hours ago
JakeJake
109212
asked 4 hours ago
JakeJake
109212
asked 4 hours ago
JakeJake
109212
asked 4 hours ago
JakeJake
109212
109212
7
Usestrtoland compare to INT_MAX/MIN.
– Eugene Sh.
4 hours ago
2
if (longvalue > INT_MAX) /* overflow */;don't forget to#include <limits.h>
– pmg
4 hours ago
1
@pmg check would fail for platforms whensizeof(int) == sizeof(long) = true.
– SergeyA
4 hours ago
1
@pmg, you can do it in a single check by just comparing for>= INT_MAX. This will always work.
– SergeyA
4 hours ago
1
@SergeyA Yeah, apparently one should handlestrtolerrors too. I assumed OP is already aware of that when mentioned usingstrtol.
– Eugene Sh.
4 hours ago
|
show 10 more comments
7
Usestrtoland compare to INT_MAX/MIN.
– Eugene Sh.
4 hours ago
2
if (longvalue > INT_MAX) /* overflow */;don't forget to#include <limits.h>
– pmg
4 hours ago
1
@pmg check would fail for platforms whensizeof(int) == sizeof(long) = true.
– SergeyA
4 hours ago
1
@pmg, you can do it in a single check by just comparing for>= INT_MAX. This will always work.
– SergeyA
4 hours ago
1
@SergeyA Yeah, apparently one should handlestrtolerrors too. I assumed OP is already aware of that when mentioned usingstrtol.
– Eugene Sh.
4 hours ago
7
7
Use
strtol and compare to INT_MAX/MIN.– Eugene Sh.
4 hours ago
Use
strtol and compare to INT_MAX/MIN.– Eugene Sh.
4 hours ago
2
2
if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>– pmg
4 hours ago
if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>– pmg
4 hours ago
1
1
@pmg check would fail for platforms when
sizeof(int) == sizeof(long) = true.– SergeyA
4 hours ago
@pmg check would fail for platforms when
sizeof(int) == sizeof(long) = true.– SergeyA
4 hours ago
1
1
@pmg, you can do it in a single check by just comparing for
>= INT_MAX. This will always work.– SergeyA
4 hours ago
@pmg, you can do it in a single check by just comparing for
>= INT_MAX. This will always work.– SergeyA
4 hours ago
1
1
@SergeyA Yeah, apparently one should handle
strtol errors too. I assumed OP is already aware of that when mentioned using strtol.– Eugene Sh.
4 hours ago
@SergeyA Yeah, apparently one should handle
strtol errors too. I assumed OP is already aware of that when mentioned using strtol.– Eugene Sh.
4 hours ago
|
show 10 more comments
2 Answers
2
active
oldest
votes
You can use strtol for this. You'll first need to check if this function fails to convert the value. If it convert successfully, then check if the value is in the range of INT_MIN to INT_MAX:
errno = 0;
long x = strtol(argv[1], NULL, 10);
if (errno) {
perror("conversion failed");
} else if (x < INT_MIN) {
printf("value too smalln");
} else if (x > INT_MAX) {
printf("value too bign");
} else {
printf("value = %ldn", x);
}
Note that this will work whether long is the same size as int or larger.
If sizeof(long) > sizeof(int), the INT_MIN and INT_MAX checks will catch the cases where the value fits in a long but not an int. If sizeof(long) == sizeof(int), an out of range value will result in errno being set to non-zero to catch the error, and the INT_MIN and INT_MAX cases will never be true.
edited 4 hours ago
Keith Thompson
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
2
Strictly speaking, it's the ranges ofintandlongthat are relevant here, not their sizes. In the presence of padding bits, it's possible forintandlongto have the same size, but forlongto have a wider range. (Few if any implementations actually use padding bits, though.)
– Keith Thompson
4 hours ago
if (errno) {is not a sufficient test to detect "conversion failed" aserrnocan still be 0.
– chux
1 hour ago
add a comment |
How should I verify that an integer value passed in from argv won't overflow?
Use strtol() and check the end pointer. Then check errno and maybe a range test
if (argc > 1) {
char *endptr;
errno = 0;
long num = strtol(argv[1], &endptr, 10);
if (argv[1] == endptr) {
puts("No conversion");
} else if (errno == ERANGE) {
puts("Value outside long range");
#if LONG_MIN < INT_MIN || LONG_MAX > INT_MAX
} else if (num < INT_MAX || num > INT_MAX) {
errno = ERANGE;
puts("Value outside int range");
#endif
} else {
// If code wants to look for trailing junk
if (*endptr) {
puts("Non-numeric text");
} else {
printf("Success %dn", (int) num);
}
}
Based on Why is there no strtoi in stdlib.h?
answered 2 hours ago
chuxchux
84.8k874157
#elseshould be#endif
– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You can use strtol for this. You'll first need to check if this function fails to convert the value. If it convert successfully, then check if the value is in the range of INT_MIN to INT_MAX:
errno = 0;
long x = strtol(argv[1], NULL, 10);
if (errno) {
perror("conversion failed");
} else if (x < INT_MIN) {
printf("value too smalln");
} else if (x > INT_MAX) {
printf("value too bign");
} else {
printf("value = %ldn", x);
}
Note that this will work whether long is the same size as int or larger.
If sizeof(long) > sizeof(int), the INT_MIN and INT_MAX checks will catch the cases where the value fits in a long but not an int. If sizeof(long) == sizeof(int), an out of range value will result in errno being set to non-zero to catch the error, and the INT_MIN and INT_MAX cases will never be true.
edited 4 hours ago
Keith Thompson
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
2
Strictly speaking, it's the ranges ofintandlongthat are relevant here, not their sizes. In the presence of padding bits, it's possible forintandlongto have the same size, but forlongto have a wider range. (Few if any implementations actually use padding bits, though.)
– Keith Thompson
4 hours ago
if (errno) {is not a sufficient test to detect "conversion failed" aserrnocan still be 0.
– chux
1 hour ago
add a comment |
You can use strtol for this. You'll first need to check if this function fails to convert the value. If it convert successfully, then check if the value is in the range of INT_MIN to INT_MAX:
errno = 0;
long x = strtol(argv[1], NULL, 10);
if (errno) {
perror("conversion failed");
} else if (x < INT_MIN) {
printf("value too smalln");
} else if (x > INT_MAX) {
printf("value too bign");
} else {
printf("value = %ldn", x);
}
Note that this will work whether long is the same size as int or larger.
If sizeof(long) > sizeof(int), the INT_MIN and INT_MAX checks will catch the cases where the value fits in a long but not an int. If sizeof(long) == sizeof(int), an out of range value will result in errno being set to non-zero to catch the error, and the INT_MIN and INT_MAX cases will never be true.
edited 4 hours ago
Keith Thompson
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
2
Strictly speaking, it's the ranges ofintandlongthat are relevant here, not their sizes. In the presence of padding bits, it's possible forintandlongto have the same size, but forlongto have a wider range. (Few if any implementations actually use padding bits, though.)
– Keith Thompson
4 hours ago
if (errno) {is not a sufficient test to detect "conversion failed" aserrnocan still be 0.
– chux
1 hour ago
add a comment |
You can use strtol for this. You'll first need to check if this function fails to convert the value. If it convert successfully, then check if the value is in the range of INT_MIN to INT_MAX:
errno = 0;
long x = strtol(argv[1], NULL, 10);
if (errno) {
perror("conversion failed");
} else if (x < INT_MIN) {
printf("value too smalln");
} else if (x > INT_MAX) {
printf("value too bign");
} else {
printf("value = %ldn", x);
}
Note that this will work whether long is the same size as int or larger.
If sizeof(long) > sizeof(int), the INT_MIN and INT_MAX checks will catch the cases where the value fits in a long but not an int. If sizeof(long) == sizeof(int), an out of range value will result in errno being set to non-zero to catch the error, and the INT_MIN and INT_MAX cases will never be true.
edited 4 hours ago
Keith Thompson
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
You can use strtol for this. You'll first need to check if this function fails to convert the value. If it convert successfully, then check if the value is in the range of INT_MIN to INT_MAX:
errno = 0;
long x = strtol(argv[1], NULL, 10);
if (errno) {
perror("conversion failed");
} else if (x < INT_MIN) {
printf("value too smalln");
} else if (x > INT_MAX) {
printf("value too bign");
} else {
printf("value = %ldn", x);
}
Note that this will work whether long is the same size as int or larger.
If sizeof(long) > sizeof(int), the INT_MIN and INT_MAX checks will catch the cases where the value fits in a long but not an int. If sizeof(long) == sizeof(int), an out of range value will result in errno being set to non-zero to catch the error, and the INT_MIN and INT_MAX cases will never be true.
edited 4 hours ago
Keith Thompson
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
edited 4 hours ago
Keith Thompson
194k26290484
edited 4 hours ago
Keith Thompson
194k26290484
edited 4 hours ago
Keith Thompson
194k26290484
194k26290484
answered 4 hours ago
dbushdbush
103k13108145
answered 4 hours ago
dbushdbush
103k13108145
answered 4 hours ago
dbushdbush
103k13108145
103k13108145
2
Strictly speaking, it's the ranges ofintandlongthat are relevant here, not their sizes. In the presence of padding bits, it's possible forintandlongto have the same size, but forlongto have a wider range. (Few if any implementations actually use padding bits, though.)
– Keith Thompson
4 hours ago
if (errno) {is not a sufficient test to detect "conversion failed" aserrnocan still be 0.
– chux
1 hour ago
add a comment |
2
Strictly speaking, it's the ranges ofintandlongthat are relevant here, not their sizes. In the presence of padding bits, it's possible forintandlongto have the same size, but forlongto have a wider range. (Few if any implementations actually use padding bits, though.)
– Keith Thompson
4 hours ago
if (errno) {is not a sufficient test to detect "conversion failed" aserrnocan still be 0.
– chux
1 hour ago
2
2
Strictly speaking, it's the ranges of
int and long that are relevant here, not their sizes. In the presence of padding bits, it's possible for int and long to have the same size, but for long to have a wider range. (Few if any implementations actually use padding bits, though.)– Keith Thompson
4 hours ago
Strictly speaking, it's the ranges of
int and long that are relevant here, not their sizes. In the presence of padding bits, it's possible for int and long to have the same size, but for long to have a wider range. (Few if any implementations actually use padding bits, though.)– Keith Thompson
4 hours ago
if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.– chux
1 hour ago
if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.– chux
1 hour ago
add a comment |
How should I verify that an integer value passed in from argv won't overflow?
Use strtol() and check the end pointer. Then check errno and maybe a range test
if (argc > 1) {
char *endptr;
errno = 0;
long num = strtol(argv[1], &endptr, 10);
if (argv[1] == endptr) {
puts("No conversion");
} else if (errno == ERANGE) {
puts("Value outside long range");
#if LONG_MIN < INT_MIN || LONG_MAX > INT_MAX
} else if (num < INT_MAX || num > INT_MAX) {
errno = ERANGE;
puts("Value outside int range");
#endif
} else {
// If code wants to look for trailing junk
if (*endptr) {
puts("Non-numeric text");
} else {
printf("Success %dn", (int) num);
}
}
Based on Why is there no strtoi in stdlib.h?
answered 2 hours ago
chuxchux
84.8k874157
#elseshould be#endif
– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
add a comment |
How should I verify that an integer value passed in from argv won't overflow?
Use strtol() and check the end pointer. Then check errno and maybe a range test
if (argc > 1) {
char *endptr;
errno = 0;
long num = strtol(argv[1], &endptr, 10);
if (argv[1] == endptr) {
puts("No conversion");
} else if (errno == ERANGE) {
puts("Value outside long range");
#if LONG_MIN < INT_MIN || LONG_MAX > INT_MAX
} else if (num < INT_MAX || num > INT_MAX) {
errno = ERANGE;
puts("Value outside int range");
#endif
} else {
// If code wants to look for trailing junk
if (*endptr) {
puts("Non-numeric text");
} else {
printf("Success %dn", (int) num);
}
}
Based on Why is there no strtoi in stdlib.h?
answered 2 hours ago
chuxchux
84.8k874157
#elseshould be#endif
– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
add a comment |
How should I verify that an integer value passed in from argv won't overflow?
Use strtol() and check the end pointer. Then check errno and maybe a range test
if (argc > 1) {
char *endptr;
errno = 0;
long num = strtol(argv[1], &endptr, 10);
if (argv[1] == endptr) {
puts("No conversion");
} else if (errno == ERANGE) {
puts("Value outside long range");
#if LONG_MIN < INT_MIN || LONG_MAX > INT_MAX
} else if (num < INT_MAX || num > INT_MAX) {
errno = ERANGE;
puts("Value outside int range");
#endif
} else {
// If code wants to look for trailing junk
if (*endptr) {
puts("Non-numeric text");
} else {
printf("Success %dn", (int) num);
}
}
Based on Why is there no strtoi in stdlib.h?
answered 2 hours ago
chuxchux
84.8k874157
How should I verify that an integer value passed in from argv won't overflow?
Use strtol() and check the end pointer. Then check errno and maybe a range test
if (argc > 1) {
char *endptr;
errno = 0;
long num = strtol(argv[1], &endptr, 10);
if (argv[1] == endptr) {
puts("No conversion");
} else if (errno == ERANGE) {
puts("Value outside long range");
#if LONG_MIN < INT_MIN || LONG_MAX > INT_MAX
} else if (num < INT_MAX || num > INT_MAX) {
errno = ERANGE;
puts("Value outside int range");
#endif
} else {
// If code wants to look for trailing junk
if (*endptr) {
puts("Non-numeric text");
} else {
printf("Success %dn", (int) num);
}
}
Based on Why is there no strtoi in stdlib.h?
answered 2 hours ago
chuxchux
84.8k874157
edited 1 hour ago
answered 2 hours ago
chuxchux
84.8k874157
answered 2 hours ago
chuxchux
84.8k874157
answered 2 hours ago
chuxchux
84.8k874157
84.8k874157
#elseshould be#endif
– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
add a comment |
#elseshould be#endif
– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
#else should be #endif– chqrlie
2 hours ago
#else should be #endif– chqrlie
2 hours ago
@chqrlie Yes, code amended.
– chux
1 hour ago
@chqrlie Yes, code amended.
– chux
1 hour ago
add a comment |
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7
Use
strtoland compare to INT_MAX/MIN.– Eugene Sh.
4 hours ago
2
if (longvalue > INT_MAX) /* overflow */;don't forget to#include <limits.h>– pmg
4 hours ago
1
@pmg check would fail for platforms when
sizeof(int) == sizeof(long) = true.– SergeyA
4 hours ago
1
@pmg, you can do it in a single check by just comparing for
>= INT_MAX. This will always work.– SergeyA
4 hours ago
1
@SergeyA Yeah, apparently one should handle
strtolerrors too. I assumed OP is already aware of that when mentioned usingstrtol.– Eugene Sh.
4 hours ago