trim function dumping core

[rkk]

Hi,

I've written a small trim function to trim away the whitespaces in a
given string. It works well with solaris forte cc compiler, but on
mingw/cygwin gcc it isn't. Here is the code:

char *trim(char *s)
{
char *begin,*end;
begin = s;
/* ltrim start */
while(*begin != '\0') {
if(isspace(*beg in)) {
begin++;
} else {
s = begin;
break;
}
}
/* ltrim end */

/* rtrim start */
end = s + strlen(s) -1;
while( end !=s && isspace(*end) ) {
end--;
}
printf("%c\n",* end);
*(end+1) = '\0';
while(*s && isspace(*s)) s++;
/* rtrim end */
return s;
}

It is failing in the line having the code *(end+1) = '\0';. I think it
may be due to portablility issues & I need this code to work on all
well known platforms & compilers. Any sugesstions/help please?

Thank you.

Regards
Kalyan

[Kohn Emil Dan]

Hi,
If this code works on Linux, Solaris, and Windows, than the day you wrote
that code was one of your luckiest days ;-))

On Thu, 6 Dec 2006, rkk wrote:

All,

Thank you for your code snippets & help provided. Here is my code which
works on Linux, Solaris & windows:

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

#define MAX_STR_LEN 4000

char *trim(char *s);
char *rtrim(char *s);
char *ltrim(char *s);

char *trim(char *s)
{
char t[MAX_STR_LEN];

<SNIPPED>

s = t;

return s;

Here you are returning a pointer to a local variable (the local array t).
The memory has been released when the function returns. The fact that it
still contains your original data and is even accessible at all is a mere
coincidence.

}

Also if you have such arbitrary limitations on the lengths of strings that
you accept (less than MAX_STR_LEN), you should check that the caller does
not pass strings larger than MAX_STR_LEN, and fail if it does so.
Emil

<SNIPPED>

[rkk]

Hi Dan,
Thanks for pointing it out. Here is the corrected code:

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

#define MAX_STR_LEN 4000

char *trim(char *s);
char *rtrim(char *s);
char *ltrim(char *s);

char *trim(char *s)
{
char *begin,*end;
begin = s;

while(*begin != '\0') {
if(isspace(*beg in)) begin++;
else {
s = begin;
break;
}
}

end = s + strlen(s) - 1;
while(end != s && isspace(*end)) end--;
*(end + 1) = '\0';
while (*s && isspace(*s)) s++;
return s;
}
char *ltrim(char *s)
{
char *begin;
begin = s;
while(*begin != '\0') {
if(isspace(*beg in)) begin++;
else {
s = begin;
break;
}
}
return s;
}

char *rtrim(char *s)
{
char *end;
end = s + strlen(s) - 1;
while(end != s && isspace(*end)) end--;
*(end + 1) = '\0';
while (*s && isspace(*s)) s++;
return s;
}

int main()
{
char str[MAX_STR_LEN] = " sample string ";
printf("Before trim str= [%s]\n",str);
strcpy(str,trim (str));
printf("After trim str= [%s]\n",str);
return 0;
}

Regards
RKK
Kohn Emil Dan wrote:

Hi,
If this code works on Linux, Solaris, and Windows, than the day you wrote
that code was one of your luckiest days ;-))

On Thu, 6 Dec 2006, rkk wrote:

All,

Thank you for your code snippets & help provided. Here is my code which
works on Linux, Solaris & windows:

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

#define MAX_STR_LEN 4000

char *trim(char *s);
char *rtrim(char *s);
char *ltrim(char *s);

char *trim(char *s)
{
char t[MAX_STR_LEN];

<SNIPPED>

s = t;

return s;

Here you are returning a pointer to a local variable (the local array t).
The memory has been released when the function returns. The fact that it
still contains your original data and is even accessible at all is a mere
coincidence.

}

Also if you have such arbitrary limitations on the lengths of strings that
you accept (less than MAX_STR_LEN), you should check that the caller does
not pass strings larger than MAX_STR_LEN, and fail if it does so.
Emil

<SNIPPED>