Segmentation fault sorry :(

Question

techno_weenie 0 Newbie Poster

14 Years Ago

Hello i'm getting a segmentation fault in my is_validport() function and could somebody people point out what i'm doing wrong please?

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <ctype.h>
#include <string.h>

/* Function definitions. */
//char *is_uid(char *s);
char *is_destportseq(char *s);
char *is_destport(char *s);
char *is_validport(char *s);
char *trimwhitespacestartandend(char *str);

/* Main method - driver. */
int main() {
    char *string = "80,  443, 8080";

    /*
        char *string2 = "65536";
        if(atoi(string2) <= 65535){
            if(0 <= atoi(string2)){
            printf("%s %s\n", string2, "Is Valid");
            }
        }else{
            printf("%s %s\n", string2, "Is NOT Valid");
        }
     */


    if (is_validport(string)) {
        printf("Valid PORTS.\n");
        return EXIT_SUCCESS;
    } else {
        printf("Invalid PORTS.\n");
        return EXIT_FAILURE;
    }

    /* The entire program is checking if our input is a sentences. */
    if (is_destportseq(string)) {
        printf("Valid sentence.\n");
        return EXIT_SUCCESS; /* Zero means success. */
    } else {
        printf("Invalid sentence.\n");
        return EXIT_FAILURE;
    }
}

char *is_destportseq(char *s) {
    char *r1, *r2; /* Report variables. */

    /* We recursively evaluate the string, passing back the pointer after each
       call. */
    r1 = is_destport(s);
    if (r1) {
        if (*r1 == 0) {
            return r1;
            /* Either it's a sentences or it isn't. */
        } else {
            if (*r1 == ',') {
                r1++;
            } else {
                return NULL;
            }
            while (*r1 == ' ') {
                r1++;
            }
            r2 = is_destportseq(r1);
            if (r2) {
                return r2;
            } else {
                return NULL;
            }
        }
    }

    return NULL;
}

char *is_destport(char *s) {
    if (!isdigit((int) * s)) {
        return NULL;
    }

    /* Remember, for a root element, you return one past. */
    while (isdigit((int) * s)) {
        s++;
    }
    return s;
}
//segmentation fault
char *is_validport(char *s) {
    char *firstport;
    char *temps;
    char *temps2;

    *temps = *s;
    //printf("s %s \n", s);
    //printf("temps %s \n", temps);
    firstport = strtok(s, ",");

    if (*s == 0) {
        return s;
    } else {
        if (atoi(firstport) <= 65535) {
            if (0 <= atoi(firstport)) {
                //printf("s = %s \n", s);
                temps2 = strstr(s, " ");
                temps2 = trimwhitespacestartandend(temps2);
                is_validport(temps2);
            }
        } else {
            return NULL;
        }
    }
    return NULL;
}

char *trimwhitespacestartandend(char *str) {
    char *end;
    // Trim leading space
    while (isspace((int) * str)) str++;
    // Trim trailing space
    end = str + strlen(str) - 1;
    while (end > str && isspace((int) * end)) end--;
    // Write new null terminator
    *(end + 1) = 0;
    return str;
}

its trying to break up a string "80, 443, 8080" into "80" "443" "8080" and make sure each number >=0 & <= 65535.

Thanks in advance.

c

2 Contributors
3 Replies
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Latest Post 14 Years Ago Latest Post by techno_weenie

Dave Sinkula 2,398 long time no c

14 Years Ago

Some lint:

--- Module: main.c (C++)
main.c 3 error 537: (Warning -- Repeated include file 'D:\Programs\CodeBlocks\MinGW\lib\gcc\mingw32\3.4.5\install-tools\include\stddef.h')
main.c 16 error 1776: (Info -- Converting a string literal to char * is not const safe (initialization))
main.c 39 error 527: (Warning -- Unreachable code at token 'if')
main.c 96 error 530: (Warning -- Symbol 'temps' (line 93) not initialized)
main.c 93 error 830: (Info -- Location cited in prior message)
main.c 104 error 668: (Warning -- Possibly passing a null pointer to function 'atoi(const char *)', arg. no. 1 [Reference: file main.c: line 99])
main.c 99 error 831: (Info -- Reference cited in prior message)
main.c 109 error 534: (Warning -- Ignoring return value of function 'is_validport(char *)' (compare with line 91))
main.c 91 error 830: (Info -- Location cited in prior message)
During Specific Walk:
File main.c line 30: is_validport(!=0)
main.c 104 error 668: (Warning -- Possibly passing a null pointer to function 'atoi(const char *)', arg. no. 1 [Reference: file main.c: line 99])
main.c 99 error 831: (Info -- Reference cited in prior message)
During Specific Walk:
File main.c line 109: is_validport(?)
main.c 104 error 668: (Warning -- Possibly passing a null pointer to function 'atoi(const char *)', arg. no. 1 [Reference: file main.c: line 99])
main.c 99 error 831: (Info -- Reference cited in prior message)
During Specific Walk:
File main.c line 108: trimwhitespacestartandend(0?)
main.c 121 error 613: (Warning -- Possible use of null pointer 'str' in argument to operator 'unary *' [Reference: file main.c: lines 107, 108])
main.c 107 error 831: (Info -- Reference cited in prior message)
main.c 108 error 831: (Info -- Reference cited in prior message)
During Specific Walk:
File main.c line 108: trimwhitespacestartandend(0?)
main.c 121 error 613: (Warning -- Possible use of null pointer 'str' in argument to operator '++' [Reference: file main.c: lines 107, 108])
main.c 107 error 831: (Info -- Reference cited in prior message)
main.c 108 error 831: (Info -- Reference cited in prior message)
During Specific Walk:
File main.c line 108: trimwhitespacestartandend(0?)
main.c 123 error 802: (Info -- Conceivably passing a null pointer to function 'strlen(const char *)', arg. no. 1 [Reference: file main.c: lines 107, 108])
main.c 107 error 831: (Info -- Reference cited in prior message)
main.c 108 error 831: (Info -- Reference cited in prior message)
During Specific Walk:
File main.c line 108: trimwhitespacestartandend(0?)
main.c 123 error 794: (Info -- Conceivable use of null pointer 'str' in left argument to operator 'ptr+int' [Reference: file main.c: lines 107, 108])
main.c 107 error 831: (Info -- Reference cited in prior message)
main.c 108 error 831: (Info -- Reference cited in prior message)

[edit]You can't write here:

char *is_validport(char *s) {
    char *firstport;
    char *temps;
    char *temps2;

    *temps = *s;

because temps doesn't point anywhere.

[edit=2]D'oh!

But you can't use strtok on a string literal:

char *string = "80,  443, 8080";

[edit=3]Do you really need all that code? Are you doing something like this?

#include <stdio.h>

void foo(const char *string)
{
   int a, b, c;
   if ( sscanf(string, "%d, %d, %d", &a, &b, &c) == 3 )
   {
      if ( a >= 0 && a <= 65535 &&
           b >= 0 && b <= 65535 &&
           c >= 0 && c <= 65535 )
      {
         printf("a = %d, b = %d, c = %d\n", a, b, c);
      }
   }
}

int main() 
{
   foo("80,  443, 8080");
   return 0;
}

/* my output
a = 80, b = 443, c = 8080
*/

Edited 14 Years Ago by Dave Sinkula because: n/a

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techno_weenie 0 Newbie Poster · Answer 1 · 2010-02-18T09:44:23+00:00

I'm sorry but I don't really understand that inorder to fix it.

Before i added

firstport = strtok(s, ",");

i had it in my main function as and i could print out the result as "80" from the original string but i don't know what i can't use it in that function.

also i've changed it so that atoi shouldn't process a null value:

char *is_validport(char *s) {
    char *firstport;
    char *temps;
    char *temps2;

    temps = s;
    //printf("s %s \n", s);
    //printf("temps %s \n", temps);
    if (*s == 0) {
        return s;
    } else {
        firstport = strtok(s, ",");
        if (*firstport == 0) {
            return s;
        } else {
            if (atoi(firstport) <= 65535) {
                if (0 <= atoi(firstport)) {
                    //printf("s = %s \n", s);
                    temps2 = strstr(s, " ");
                    temps2 = trimwhitespacestartandend(temps2);
                    is_validport(temps2);
                }
            } else {
                return NULL;
            }
        }
    }
    return NULL;
}

techno_weenie 0 Newbie Poster · Answer 2 · 2010-02-18T09:50:36+00:00

I would do it like [edit=3] however i don't know how many different numbers i will get so i was doing it recursively. As the string is valid as long as it matchs this BNF grammar

It will make sure the string is valid for the grammar. the problem is making sure each port >=0 & <= 65535 for a n number of ports