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

[pete]

rkk wrote:

>
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?

/* BEGIN new.c */

#include <stdio.h>
#include <ctype.h>

char *trim(char *s1);

int main(void)
{
char string[] = "This is a string with tabs \t\t and spaces"
" and\rother space\fcharacte rs\v.";

puts(trim(strin g));
return 0;
}

char *trim(char *s1)
{
char *const p1 = s1;
char *p2;

for (p2 = s1; *s1 != '\0'; ++s1) {
if (!isspace((unsi gned char)*s1)) {
*p2++ = *s1;
}
}
*p2 = '\0';
return p1;
}

/* END new.c */
--
pete

[Richard Heathfield]

rkk said:

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.

Could you please provide some test data that is known to fail? In the
meantime, let's try it with the empty string - always a good test.

Here is the code:

....and your tabbed indenting was stripped out somewhere along the line -
probably by my client. I've mended it kinda...

>
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 */

Okay, the empty string will skip right around that first loop, and go on to
here...

/* rtrim start */
end = s + strlen(s) -1;

Whoops, there's a bug already. s + 0 - 1 is s - 1, which is an invalid
pointer. Fix that, and let us know if you still have problems. If so, give
us the latest code and some test data that is known to fail.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[Chris Dollin]

rkk wrote:

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;
}

Um. Er. "Small"? Don't you think that this is just a bit big
for left-and-right trimming?

Here's my effort, which I offer as a target ...

#include <stdio.h>
#include <ctype.h>

char *trim( char *s )
{
char *lastNonSpace = 0;
char *current;
while (isspace( *s )) s += 1;
current = s;
while (*current)
{
if (!isspace( *current )) lastNonSpace = current;
current += 1;
}
if (lastNonSpace) lastNonSpace[1] = 0;
return s;
}

int main( int argc, char **argv )
{
char e1[] = "";
char e2[] = "1";
char e3[] = "spoo";
char e4[] = " spoo ";
char e5[] = " spoo for tea! ";
char e6[] = " theLongAndWindi ngRoad";
fprintf( stderr, "'%s'\n", trim( e1 ) );
fprintf( stderr, "'%s'\n", trim( e2 ) );
fprintf( stderr, "'%s'\n", trim( e3 ) );
fprintf( stderr, "'%s'\n", trim( e4 ) );
fprintf( stderr, "'%s'\n", trim( e5 ) );
fprintf( stderr, "'%s'\n", trim( e6 ) );
return 0;
}

Notes:

`0` aka `'\0'` is not a space character. Hence the first loop
will terminate safely, at either the end of the string or
on its first non-space character.

If `lastNonSpace` is not null, it is always legal to
assign to `lastNonSpace[1]`. Either the last non-space
was the last character of the string, in which case
`lastNonSpace+1 ` points to the terminating null, or
it isn't, in which case `lastNonSpace+1 ` points to
a space.

This `trim` updates the passed string. Hence it must
not be used on string literals. Hence the examples
in `main` are string /array/ objects /initialised
from/ string literals.

--
Chris "Perikles triumphant" Dollin
Meaning precedes definition.

[rkk]

Chris Dollin wrote:

rkk wrote:

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;
}

Um. Er. "Small"? Don't you think that this is just a bit big
for left-and-right trimming?

Here's my effort, which I offer as a target ...

#include <stdio.h>
#include <ctype.h>

char *trim( char *s )
{
char *lastNonSpace = 0;
char *current;
while (isspace( *s )) s += 1;
current = s;
while (*current)
{
if (!isspace( *current )) lastNonSpace = current;
current += 1;
}
if (lastNonSpace) lastNonSpace[1] = 0;
return s;
}

int main( int argc, char **argv )
{
char e1[] = "";
char e2[] = "1";
char e3[] = "spoo";
char e4[] = " spoo ";
char e5[] = " spoo for tea! ";
char e6[] = " theLongAndWindi ngRoad";
fprintf( stderr, "'%s'\n", trim( e1 ) );
fprintf( stderr, "'%s'\n", trim( e2 ) );
fprintf( stderr, "'%s'\n", trim( e3 ) );
fprintf( stderr, "'%s'\n", trim( e4 ) );
fprintf( stderr, "'%s'\n", trim( e5 ) );
fprintf( stderr, "'%s'\n", trim( e6 ) );
return 0;
}

Notes:

`0` aka `'\0'` is not a space character. Hence the first loop
will terminate safely, at either the end of the string or
on its first non-space character.

If `lastNonSpace` is not null, it is always legal to
assign to `lastNonSpace[1]`. Either the last non-space
was the last character of the string, in which case
`lastNonSpace+1 ` points to the terminating null, or
it isn't, in which case `lastNonSpace+1 ` points to
a space.

This `trim` updates the passed string. Hence it must
not be used on string literals. Hence the examples
in `main` are string /array/ objects /initialised
from/ string literals.

Chris "Perikles triumphant" Dollin
Meaning precedes definition.

This code doesn't work on my machine. Seems to be broken somewhere.

Thanks for your effort.

Cheers
Kalyan

[santosh]

rkk wrote:

Chris Dollin wrote:

rkk wrote:

<snip>

I've written a small trim function to trim away the whitespaces in a
given string.

<snip>

Um. Er. "Small"? Don't you think that this is just a bit big
for left-and-right trimming?

Here's my effort, which I offer as a target ...

#include <stdio.h>
#include <ctype.h>

char *trim( char *s )
{
char *lastNonSpace = 0;
char *current;
while (isspace( *s )) s += 1;
current = s;
while (*current)
{
if (!isspace( *current )) lastNonSpace = current;
current += 1;
}
if (lastNonSpace) lastNonSpace[1] = 0;
return s;
}

int main( int argc, char **argv )
{
char e1[] = "";
char e2[] = "1";
char e3[] = "spoo";
char e4[] = " spoo ";
char e5[] = " spoo for tea! ";
char e6[] = " theLongAndWindi ngRoad";
fprintf( stderr, "'%s'\n", trim( e1 ) );
fprintf( stderr, "'%s'\n", trim( e2 ) );
fprintf( stderr, "'%s'\n", trim( e3 ) );
fprintf( stderr, "'%s'\n", trim( e4 ) );
fprintf( stderr, "'%s'\n", trim( e5 ) );
fprintf( stderr, "'%s'\n", trim( e6 ) );
return 0;
}

<snip>

This code doesn't work on my machine. Seems to be broken somewhere.

It compiles fine and appears to work well enough here. A couple of
warnings about unused argc and argv are produced.

[Richard Heathfield]

rkk said:

<snip>

>
This code doesn't work on my machine.

Symptoms?
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[Chris Dollin]

rkk wrote:

Chris Dollin wrote:

(fx:snip)

>#include <stdio.h>
#include <ctype.h>

char *trim( char *s )

(fx:snip more)

This code doesn't work on my machine. Seems to be broken somewhere.

Hell's teeth, man, can't you be more explicit? What were the
symptoms? What implementation are you using? What, if any,
were the compiler messages? What was the output? Did you compile
the code exactly as I posted it?

If there's a mistake in it, I'd like to know where, but since
my crystal ball is back being repaired right now, I don't
know where to start ...

--
Chris "Perikles triumphant" Dollin
"We did not have time to find out everything we wanted to know."
- James Blish, /A Clash of Cymbals/

[Fred Kleinschmidt]

"Chris Dollin" <ch**********@h p.comwrote in message
news:el******** **@murdoch.hpl. hp.com...

rkk wrote:

>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;
}

Um. Er. "Small"? Don't you think that this is just a bit big
for left-and-right trimming?

Here's my effort, which I offer as a target ...

#include <stdio.h>
#include <ctype.h>

char *trim( char *s )
{
char *lastNonSpace = 0;
char *current;
while (isspace( *s )) s += 1;
current = s;
while (*current)
{
if (!isspace( *current )) lastNonSpace = current;
current += 1;
}
if (lastNonSpace) lastNonSpace[1] = 0;
return s;
}

int main( int argc, char **argv )
{
char e1[] = "";
char e2[] = "1";
char e3[] = "spoo";
char e4[] = " spoo ";
char e5[] = " spoo for tea! ";
char e6[] = " theLongAndWindi ngRoad";
fprintf( stderr, "'%s'\n", trim( e1 ) );
fprintf( stderr, "'%s'\n", trim( e2 ) );
fprintf( stderr, "'%s'\n", trim( e3 ) );
fprintf( stderr, "'%s'\n", trim( e4 ) );
fprintf( stderr, "'%s'\n", trim( e5 ) );
fprintf( stderr, "'%s'\n", trim( e6 ) );
return 0;
}

Notes:

`0` aka `'\0'` is not a space character. Hence the first loop
will terminate safely, at either the end of the string or
on its first non-space character.

If `lastNonSpace` is not null, it is always legal to
assign to `lastNonSpace[1]`. Either the last non-space
was the last character of the string, in which case
`lastNonSpace+1 ` points to the terminating null, or
it isn't, in which case `lastNonSpace+1 ` points to
a space.

This `trim` updates the passed string. Hence it must
not be used on string literals. Hence the examples
in `main` are string /array/ objects /initialised
from/ string literals.

--
Chris "Perikles triumphant" Dollin
Meaning precedes definition.

What happens here?

int main( int argc, char **argv ) {
fprintf( stderr, "'%s'\n", trim(NULL) );
return 0;
}

--
Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project

[Chris Dollin]

Fred Kleinschmidt wrote:

"Chris Dollin" <ch**********@h p.comwrote in message

(fx:snip)

>char *trim( char *s )
{
char *lastNonSpace = 0;
char *current;
while (isspace( *s )) s += 1;
current = s;
while (*current)
{
if (!isspace( *current )) lastNonSpace = current;
current += 1;
}
if (lastNonSpace) lastNonSpace[1] = 0;
return s;
}

(fx:snip more)

What happens here?

int main( int argc, char **argv ) {
fprintf( stderr, "'%s'\n", trim(NULL) );
return 0;
}

Undefined behaviour. I should have documented that `trim` expects
a string. (So does the OPs `trim`.)

--
Chris "Perikles triumphant" Dollin
"It took a very long time, much longer than the most generous estimates."
- James White, /Sector General/