I am writing a function to combine strings, but when I execute I get a segmentation fault, which doesn't make sence. Segmentation fault is when you try to acess a point of memory that doesn't exist, like trying to acess array[10] when you declared array[7].
Here is the source code:
Code:
#include <stdio.h>
/* #include <string.h> == cheating! */
#define MAXINPUT 1000
char combine(char string1[MAXINPUT], char string2[MAXINPUT]) {
int count1, count2 = 0;
while (string1[count1] != '\0')
++count1;
while (string2[count2] != '\0')
string1[count1++] = string2[count2++];
string1[count1] = '\0';
}
main() {
char string1[MAXINPUT];
char string2[MAXINPUT];
int i = 0;
printf("Enter two strings each under 1000 characters:\n");
while(i = 0) {
printf("1: ");
scanf("%s", string1);
if ((sizeof string1) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
i = 1;
}
i = 0;
while(i = 0) {
printf("\n2: ");
scanf("%s", string2);
if ((sizeof string2) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
i = 1;
}
printf("%s and %s combined is %s", string1, string2, combine(string1, string2));
return 0;
}
I know there are functions in the string.h header, but as you can see, I wanted to do it without them, thus calling those functions "cheating".
(sizeof string1) is a constant and will not vary depending on the contents of string1. And what if 1200 characters were entered? Where do you think the extra 200 will be? You seem to be intentionally blowing arrays.
But your problem is the combine routine. It returns a character, not a string. Or it would had you returned *anything*. Then you use this character as a pointer to character. It looks like you might mean for combine to return a pointer to character. If so, define it that way and put in a return statement.
But your problem is the combine routine. It returns a character, not a string. Or it would had you returned *anything*. Then you use this character as a pointer to character. It looks like you might mean for combine to return a pointer to character. If so, define it that way and put in a return statement.
I'm sorry, but what does that have to do with the segmentation fault?
char combine(char string1[MAXINPUT], char string2[MAXINPUT]) {
int count1, count2 = 0;
while (string1[count1] != '\0')
++count1;
while (string2[count2] != '\0')
string1[count1++] = string2[count2++];
string1[count1] = '\0';
}
the function is declared as returning char; however there is no return statement that actually returns a char. In this case the function will return a "garbage" value even if the syntax is not necessarily incorrect!
2.nd problem:
Code:
..
printf("Enter two strings each under 1000 characters:\n");
while(i = 0) { // should be while (i == 0)
printf("1: ");
scanf("%s", string1);
if ((sizeof string1) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
i = 1;
}
i = 0;
while(i = 0) { // should be while (i == 0)
printf("\n2: ");
scanf("%s", string2);
if ((sizeof string2) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
...
Thanks milhan, you explained it better. I still get a segmentation fault that I don't understand, the current source (almost same as before) :
Code:
#include <stdio.h>
/* #include <string.h> == cheating! */
#define MAXINPUT 1000
char combine(char string1[MAXINPUT], char string2[MAXINPUT]) {
int count1, count2 = 0;
while (string1[count1] != '\0')
++count1;
while (string2[count2] != '\0')
string1[count1++] = string2[count2++];
string1[count1] = '\0';
return string1;
}
main() {
char string1[MAXINPUT];
char string2[MAXINPUT];
int i = 0;
printf("Enter two strings each under 1000 characters:\n");
while(i == 0) {
printf("1: ");
scanf("%s", string1);
if ((sizeof string1) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
i = 1;
}
i = 0;
while(i == 0) {
printf("2: ");
scanf("%s", string2);
if ((sizeof string2) > MAXINPUT) {
i = 0;
printf("I said under 1000 characters, please enter it again:\n");
}
else
i = 1;
}
printf("%s and %s combined is %s", string1, string2, combine(string1, string2));
return 0;
}
I get an erorr related to
Code:
return string1;
Which is exactly as put:
Code:
combine-strings.c:15: warning: return makes integer from pointer without a cast
so, I assume that I could redeclare string1 as an int, to make the program compile, even though it wouldn't run correctly, because int is numbers(it can be ascii, but that adds up fast), and char is text. So I declare string1 like:
Code:
return (int) string1;
and I get a segmentaton fault after I enter the two strings. I assume that the int was the problem, so I try a few other examples:
Code:
return string1[0];
Which produces segmentation erorr when executed.
Code:
return string1[MAXLINE];
Also produces segmentation erorr when executed.
The odd part is I don't seem to be asking for a part of memory that doesn't exist.
octal look at your combine(char [], char[]) function again. I didn't see it at my previous post either.
Code:
char combine(char string1[MAXINPUT], char string2[MAXINPUT]) {
int count1, count2 = 0; // you didn't initialize count1, so=> int count1 = 0, count2 = 0;
while (string1[count1] != '\0')
++count1;
while (string2[count2] != '\0')
string1[count1++] = string2[count2++];
string1[count1] = '\0';
return string1;
}
Quote:
Code:
return string1[0];
Which produces segmentation erorr when executed.
return string1[0] is correct. The segmentation fault can't come from here. Try running again with the correction in the combine func. and return string1[0]..
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