{"id":26193,"date":"2017-10-26T20:24:48","date_gmt":"2017-10-26T14:54:48","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=26193"},"modified":"2017-10-26T20:24:48","modified_gmt":"2017-10-26T14:54:48","slug":"c-programming-check-integer-overflow","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/c-programming-check-integer-overflow\/","title":{"rendered":"C Programming-Check for Integer Overflow"},"content":{"rendered":"

Write a \u201cC\u201d function, int addOvf(int* result, int a, int b) If there is no overflow, the function places the resultant = sum a+b in \u201cresult\u201d and returns 0. Otherwise it returns -1. The solution of casting to long and adding to find detecting the overflow is not allowed.
\nMethod 1<\/strong>
\nThere can be overflow only if signs of two numbers are same, and sign of sum is opposite to the signs of numbers.<\/p>\n

1)  Calculate sum\r\n2)  If both numbers are positive and sum is negative then return -1\r\n     Else \r\n        If both numbers are negative and sum is positive then return -1\r\n        Else return 0<\/pre>\n
 
 C Programming<\/span> <\/div> 
#include<stdio.h>#include<stdlib.h> \/* Takes pointer to result and two numbers as    arguments. If there is no overflow, the function    places the resultant = sum a+b in \u201cresult\u201d and    returns 0, otherwise it returns -1 *\/ int addOvf(int* result, int a, int b) {     *result = a + b;     if(a > 0 && b > 0 && *result < 0)         return -1;     if(a < 0 && b < 0 && *result > 0)         return -1;     return 0; }  int main() {     int *res = (int *)malloc(sizeof(int));     int x = 2147483640;     int y = 10;      printf("%d", addOvf(res, x, y));      printf("\\n %d", *res);     getchar();     return 0;}<\/code><\/pre> <\/div>\n
Time Complexity :<\/strong> O(1)
\nSpace Complexity:<\/strong> O(1)<\/p>\n[ad type=”banner”]\n
Method 2<\/strong>
\nThanks to Himanshu Aggarwal for adding this method. This method doesn\u2019t modify *result if there us an overflow.<\/p>\n
 
 C Programming<\/span> <\/div> 
#include<stdio.h>#include<limits.h>#include<stdlib.h> int addOvf(int* result, int a, int b){   if( a > INT_MAX - b)     return -1;   else   {     *result = a + b;      return 0;   }} int main(){  int *res = (int *)malloc(sizeof(int));  int x = 2147483640;  int y = 10;   printf("%d", addOvf(res, x, y));  printf("\\n %d", *res);  getchar();  return 0;}<\/code><\/pre> <\/div>\n
Time Complexity :<\/strong> O(1)
\nSpace Complexity:<\/strong> O(1)<\/p>\n[ad type=”banner”]\n","protected":false},"excerpt":{"rendered":"
C Programming Check for Integer Overflow – Bit Algorithm – The solution of casting to long and adding to find detecting the overflow is not allowed.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[69969,74852,69866,1],"tags":[77713,77728,77712,77721,77705,77707,77745,77706,77727,77730,77746,77735,77738,77736,77722,77744,77747,77709,77719,77741,77733,77739,77724,77726,77704,77711,77732,77731,77703,77734,74445,77725,77720,77737,77718,77742,77723,77715,77716,77700,77714,77710,77717,77708,77743,77729,77701,77702,77740,75264],"class_list":["post-26193","post","type-post","status-publish","format-standard","hentry","category-algorithm","category-bit-algorithms","category-c-programming","category-coding","tag-16-bit-range","tag-16-bit-signed-integer-converter","tag-64-bit-long","tag-buffer-c","tag-buffer-overflow","tag-buffer-overflow-attack-example","tag-buffer-overflow-example","tag-buffer-overflow-vulnerability","tag-buffer-overrun","tag-c-buffer","tag-c-char","tag-c-char-type","tag-c-int","tag-c-language-float","tag-c-long-long","tag-c-programming-data-types","tag-c-short","tag-c-short-type","tag-c-uint","tag-datatypes-of-c","tag-double-c-language","tag-double-c-programming","tag-double-data-type-c","tag-float-long-double","tag-function-of-buffer","tag-how-to-check-for-overflow","tag-int-32-max","tag-int-32-range","tag-int-c","tag-int-c-programming","tag-integers-examples","tag-integers-test","tag-long-32-bit","tag-long-c-programming","tag-long-data-type-c","tag-long-double-float","tag-long-integer-range","tag-long-long-c","tag-long-long-double","tag-long-long-in-c","tag-long-long-limit","tag-max-int32","tag-overflow-detection","tag-short-type-c","tag-size-of-float","tag-size-of-long","tag-stack-in-c-programming","tag-stack-program-in-c","tag-type-char","tag-unsigned-int-in-c"],"_links":{"self":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/26193","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/comments?post=26193"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/26193\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=26193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=26193"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=26193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}