How should I verify that an integer value passed in from argv won't overflow?












6















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







share|improve this question


















  • 7





    Use strtol and compare to INT_MAX/MIN.

    – Eugene Sh.
    6 hours ago






  • 2





    if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

    – pmg
    6 hours ago






  • 1





    @pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

    – SergeyA
    6 hours ago








  • 1





    @pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

    – SergeyA
    6 hours ago






  • 1





    @SergeyA Yeah, apparently one should handle strtol errors too. I assumed OP is already aware of that when mentioned using strtol.

    – Eugene Sh.
    6 hours ago
















6















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







share|improve this question


















  • 7





    Use strtol and compare to INT_MAX/MIN.

    – Eugene Sh.
    6 hours ago






  • 2





    if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

    – pmg
    6 hours ago






  • 1





    @pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

    – SergeyA
    6 hours ago








  • 1





    @pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

    – SergeyA
    6 hours ago






  • 1





    @SergeyA Yeah, apparently one should handle strtol errors too. I assumed OP is already aware of that when mentioned using strtol.

    – Eugene Sh.
    6 hours ago














6












6








6


0






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







share|improve this question














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






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 6 hours ago









JakeJake

109212




109212








  • 7





    Use strtol and compare to INT_MAX/MIN.

    – Eugene Sh.
    6 hours ago






  • 2





    if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

    – pmg
    6 hours ago






  • 1





    @pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

    – SergeyA
    6 hours ago








  • 1





    @pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

    – SergeyA
    6 hours ago






  • 1





    @SergeyA Yeah, apparently one should handle strtol errors too. I assumed OP is already aware of that when mentioned using strtol.

    – Eugene Sh.
    6 hours ago














  • 7





    Use strtol and compare to INT_MAX/MIN.

    – Eugene Sh.
    6 hours ago






  • 2





    if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

    – pmg
    6 hours ago






  • 1





    @pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

    – SergeyA
    6 hours ago








  • 1





    @pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

    – SergeyA
    6 hours ago






  • 1





    @SergeyA Yeah, apparently one should handle strtol errors too. I assumed OP is already aware of that when mentioned using strtol.

    – Eugene Sh.
    6 hours ago








7




7





Use strtol and compare to INT_MAX/MIN.

– Eugene Sh.
6 hours ago





Use strtol and compare to INT_MAX/MIN.

– Eugene Sh.
6 hours ago




2




2





if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

– pmg
6 hours ago





if (longvalue > INT_MAX) /* overflow */; don't forget to #include <limits.h>

– pmg
6 hours ago




1




1





@pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

– SergeyA
6 hours ago







@pmg check would fail for platforms when sizeof(int) == sizeof(long) = true.

– SergeyA
6 hours ago






1




1





@pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

– SergeyA
6 hours ago





@pmg, you can do it in a single check by just comparing for >= INT_MAX. This will always work.

– SergeyA
6 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.
6 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.
6 hours ago












2 Answers
2






active

oldest

votes


















5














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.






share|improve this answer





















  • 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
    6 hours ago











  • if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

    – chux
    3 hours ago



















1















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?






share|improve this answer


























  • #else should be #endif

    – chqrlie
    3 hours ago











  • @chqrlie Yes, code amended.

    – chux
    3 hours ago












Your Answer






StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55462918%2fhow-should-i-verify-that-an-integer-value-passed-in-from-argv-wont-overflow%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









5














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.






share|improve this answer





















  • 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
    6 hours ago











  • if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

    – chux
    3 hours ago
















5














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.






share|improve this answer





















  • 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
    6 hours ago











  • if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

    – chux
    3 hours ago














5












5








5







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.






share|improve this answer















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.







share|improve this answer














share|improve this answer



share|improve this answer








edited 6 hours ago









Keith Thompson

194k26290484




194k26290484










answered 6 hours ago









dbushdbush

103k13108145




103k13108145








  • 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
    6 hours ago











  • if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

    – chux
    3 hours ago














  • 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
    6 hours ago











  • if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

    – chux
    3 hours 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
6 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
6 hours ago













if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

– chux
3 hours ago





if (errno) { is not a sufficient test to detect "conversion failed" as errno can still be 0.

– chux
3 hours ago













1















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?






share|improve this answer


























  • #else should be #endif

    – chqrlie
    3 hours ago











  • @chqrlie Yes, code amended.

    – chux
    3 hours ago
















1















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?






share|improve this answer


























  • #else should be #endif

    – chqrlie
    3 hours ago











  • @chqrlie Yes, code amended.

    – chux
    3 hours ago














1












1








1








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?






share|improve this answer
















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?







share|improve this answer














share|improve this answer



share|improve this answer








edited 3 hours ago

























answered 3 hours ago









chuxchux

84.8k874157




84.8k874157













  • #else should be #endif

    – chqrlie
    3 hours ago











  • @chqrlie Yes, code amended.

    – chux
    3 hours ago



















  • #else should be #endif

    – chqrlie
    3 hours ago











  • @chqrlie Yes, code amended.

    – chux
    3 hours ago

















#else should be #endif

– chqrlie
3 hours ago





#else should be #endif

– chqrlie
3 hours ago













@chqrlie Yes, code amended.

– chux
3 hours ago





@chqrlie Yes, code amended.

– chux
3 hours ago


















draft saved

draft discarded




















































Thanks for contributing an answer to Stack Overflow!


  • Please be sure to answer the question. Provide details and share your research!

But avoid …



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55462918%2fhow-should-i-verify-that-an-integer-value-passed-in-from-argv-wont-overflow%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







-

Popular posts from this blog

Bundesstraße 106

Image
Dieser Artikel beschreibt die Bundesstraße 106 in Deutschland. Zur gleichnamigen Straße in Österreich siehe Mölltal Straße. Vorlage:Infobox hochrangige Straße/Wartung/DE-B Bundesstraße 106 in Deutschland Karte Basisdaten Betreiber: Deutschland  Bundesrepublik Deutschland Straßenbeginn: Wismar ( 53° 54′  N , 11° 24′  O 53.900536 11.396875 ) Straßenende: Schwerin ( 53° 36′  N , 11° 24′  O 53.592785 11.404892 ) Gesamtlänge: 40,7 km Bundesland: Mecklenburg-Vorpommern Ausbauzustand: zweistreifig [1] Bundesstraße 106 in Schwerin (Umgehungsstraße) Straßenverlauf Land Mecklenburg-Vorpommern Landkreis Nordwestmecklenburg Ortsumgehung Wismar Wallensteingraben über   Dorf Mecklenburg Wallensteingraben Groß Stieten Bad Kleinen OT Niendorf Bahnstrecke Lübeck–Bad Kleinen Zickhusen Lübstorf Klein Trebbow OT Kirch Stück
Read more

Verónica Boquete

Image
Verónica Boquete im Trikot der Nationalmannschaft (2013) Personalia Name Verónica Boquete Giadans Geburtstag 9. April 1987 Geburtsort Santiago de Compostela, Spanien Größe 159 cm Position Mittelfeld / Sturm Juniorinnen Jahre Station 2001–2005 Xuventú Aguiño Frauen Jahre Station Spiele (Tore) 1 2005–2008 Prainsa Zaragoza 83 (40) 2008–2010 Espanyol Barcelona 53 (30) 2010 Buffalo Flash 9 0 (9) 2010 Chicago Red Stars 3 0 (1) 2010–2011 Espanyol Barcelona 26 (41) 2011 Philadelphia Independence 13 0 (5) 2011 Energija Woronesch 5 0 (1) 2012–2014 Tyresö FF 39 (14) 2014 Portland Thorns FC 15 0 (4) 2014–2015 1. FFC Frankfurt 23 0 (7) 2015–2016 FC Bayern München 9 0 (0) 2016–2018 Paris Saint-Germain 31 0 (8) 2018 Peking BG Phoenix 2019– Utah Royals FC 0 0 (0) Nationalmannschaft Jahre Auswahl
Read more

Ida-Boy-Ed-Garten

Image
Die Lage des Ida-Boy-Ed-Gartens, rot markiert Der Ida-Boy-Ed-Garten Der Ida-Boy-Ed-Garten, Blick von der Wakenitzmauer durch das Tor in der Stadtmauer Der Ida-Boy-Ed-Garten ist eine Straße der Lübecker Altstadt. Inhaltsverzeichnis 1 Lage 2 Geschichte 3 Literatur 4 Weblinks Lage | Der etwa 90 Meter lange Ida-Boy-Ed-Garten befindet sich an der nördlichen Spitze der Altstadtinsel, vor dem Burgtor. Die in einem Bogen durch eine Grünanlage hangaufwärts führende Straße verbindet die Wakenitzmauer mit der Burgtorbrücke. Geschichte | Der heutige Ida-Boy-Ed-Garten wurde ursprünglich als Verlängerung der Wakenitzmauer angelegt. 1903 wurde in den erhaltenen Teil der mittelalterlichen Stadtmauer, an dem die Wakenitzmauer bei der Einmündung der Kaiserstraße begann, ein Tor mit einem großen Bogen für die Durchführung der Straße und zwei kleineren seitlichen Öffnungen für Fußgänger gebrochen, um für die neu errichteten Wohnhäuser in diesem Bereich
Read more