New to C: Getting Application error when running program

[Mike Polinske]

I am new to the C programming language but have been programming in
Cobol for over 10 years. When I compile the following code, it
compiles clean but I get an application error both under Windows XP and
Win2K.

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

char title[] = "Year End Report";

char work_buffer[51];

main()
{
strcpy(work_buf fer,title);
strncenter(work _buffer,50);
printf("%s\n",w ork_buffer);
strljust(work_b uffer);
printf("%s\n",w ork_buffer);
strrjust(work_b uffer);
printf("%s\n",w ork_buffer);
}

/* Left justify a string */
strljust(str)
char *str;
{
int len;

len = strlen(str);
while (isspace(str) != 0) {
memmove (str,str + 1,len);
str[len] = ' ';
}
}

/* Reverse a string */
strrev(str)
char *str;
{
char ch;
char *end;

end = str + strlen(str) - 1;

while (str < end) {
ch = *end;
*end-- = *str;
*str++ = ch;
}
}

/* Right justify a string */
strrjust(str)
char *str;
{
strrev(str);
strljust(str);
strrev(str);
}

/* Truncate to last non-white character */
strtrunc(str)
char *str;
{
char *end;

end = str + strlen(str) - 1;

while ((*str != 0) && (isspace (*end) != 0)) {
*end-- = 0;
}
}

/* Pad a string for len with spaces */
struntrunc(str, len)
char *str;
int len;
{
while (strlen (str) < len) {
strcat (str,' ');
}
}

/* Center a string */
strcenter(str)
char *str;
{
strncenter (str, strlen(str));
}

/* Center a string within width */
strncenter(str, width)
char *str;
int width;
{
int non_blank_len, padding;

strtrunc (str);
strrev (str);
strtrunc (str);
non_blank_len = strlen (str);

padding = (width - non_blank_len) / 2;

struntrunc (str,padding);
strrev (str);
struntrunc (str,width);
}

It seems to be blowing up in the struntrunc function, but I can't
understand why. I know that this program is trying to take a string,
center it, left justify it and right justify it.

Any ideas on how I can get this program to run?

I am using Open Watcom C/C++ 1.4 but I had the same problem when I
tried it with OW 1.3.

Thanks

[lothar.behrens]

Be sure, there will be no buffer overrun. Try a buffer with 52 or some
more chars.

Yust a thought :-)

Lothar

[Mark McIntyre]

On 17 Jan 2006 14:47:28 -0800, in comp.lang.c , "Mike Polinske"
<mp******@execp c.com> wrote:

compiles clean but I get an application error both under Windows XP and
Win2K.
Turn warninglevels up to max on your compiler. There are several
coding errors that ought to have been alerted to you.
#include <stdio.h>
#include <ctype.h>

char title[] = "Year End Report";
char work_buffer[51];
no need for these to be globals, they can be inside main.
main()
{
strcpy(work_buf fer,title);
you should get a warning from your compiler here - you need a
declaration of strcpy() in scope, usually provided by #include
<string.h>
strncenter(work _buffer,50);
you have the same problem here. Put a prototype for strncenter()
before the start of main.

Also, its a bad idea to name functions str followed by a lower case
letter. Such names are reserved for the compiler. strCenter would be
ok tho, or str_center.
printf("%s\n",w ork_buffer);
strljust(work_b uffer);
printf("%s\n",w ork_buffer);
strrjust(work_b uffer);
printf("%s\n",w ork_buffer);
}

/* Left justify a string */
strljust(str )
char *str;
this style of function definition is 20 years out of date. The normal
modern style is
void strladjust(char *str)

There's two differences here - firstly your original function was
implicitly returning an int, which is permissible but deprecated ;
secondly, you should include the parameter type in the parens.

Also, a function must return something, unless its declared void.
Yours is declared as returning an int, but doesn't return anything.
Oops!
{
int len;

len = strlen(str);
while (isspace(str) != 0) {
isspace() expects a single character - str is a string.
Did you mean *str. ?
memmove (str,str + 1,len);
str[len] = ' ';
}
}

/* Reverse a string */
strrev(str)
char *str;
this name may conflict with a builtin library function. Did this
actually compile?
struntrunc(str ,len)
char *str;
int len;
{
while (strlen (str) < len) {
strcat (str,' ');

strcat requires the 2nd parameter to be a string, not a char.
strcat(str, " ");

by the way, one can do this entire operation much more simply with
sprintf()

Mark McIntyre
--

[Flash Gordon]

Mike Polinske wrote:

I am new to the C programming language but have been programming in
Cobol for over 10 years. When I compile the following code, it
compiles clean but I get an application error both under Windows XP and
Win2K.

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

char title[] = "Year End Report";

char work_buffer[51];

main()
Main returns an int, and as you are not using the optional parameters it
is better to say so explicitly.

int main(void)
{
strcpy(work_buf fer,title);
strncenter(work _buffer,50);
printf("%s\n",w ork_buffer);
strljust(work_b uffer);
printf("%s\n",w ork_buffer);
strrjust(work_b uffer);
printf("%s\n",w ork_buffer);
Main returns an int, so return an int!
return 0;
}

/* Left justify a string */
strljust(str)
char *str;
Replace whatever resource you are learning from. That style went out in
1989. Use the prototype style instead

strljust(char *str)

Also, add a prototype definition before main so that the compiler is
required to validate the parameters.

Also, function names starting str followed by a lower case letter are
reserved, so you should pick a different name. Possibly str_ljust.
{
int len;

len = strlen(str);
while (isspace(str) != 0) {
Why not simply
while (isspace(str))
?
memmove (str,str + 1,len);
str[len] = ' ';
C arrays are indexed from 0 not from 1, so this is your problem. You are
overwriting the null termination of the string instead of the last
non-null character.
}
Also, why not work out how far you need to move it then move it all the
way in one go? I know we say don't optimise until you know you have a
problem, but there is no need to go overboard and make it obviously
inefficient!
}

/* Reverse a string */
strrev(str)
char *str;
Same comments as before.
{
char ch;
char *end;

end = str + strlen(str) - 1;

while (str < end) {
ch = *end;
*end-- = *str;
*str++ = ch;
}
}

/* Right justify a string */
strrjust(str)
char *str;
Same comments.
{
strrev(str);
strljust(str);
strrev(str);
}

/* Truncate to last non-white character */
strtrunc(str)
char *str;
Same comments again.

<snip unchecked additional code>
It seems to be blowing up in the struntrunc function, but I can't
understand why. I know that this program is trying to take a string,
center it, left justify it and right justify it.

Any ideas on how I can get this program to run?
First fix everything I (and anyone else who responds) have pointed out,
then go through the code looking for any other similar errors. I've
you've made a given class of mistakes once yoy may well have made it
more than once.
I am using Open Watcom C/C++ 1.4 but I had the same problem when I
tried it with OW 1.3.

On comp.lang.c the compiler is irrelevant since we only deal with
standard C. However, your problem looks to be with standard C rather
than the compiler, so it is perfectly on topic in comp.lang.c
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[Roberto Waltman]

<mp******@execp c.com> wrote:

I am new to the C programming language but have been programming in
Cobol for over 10 years. When I compile the following code, it
compiles clean but I get an application error both under Windows XP and
Win2K.

In addition to what others pointed out re: "old style" declarations,
these are the few errors I can see:

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

char title[] = "Year End Report";

char work_buffer[51];

main()
{
strcpy(work_buf fer,title);
strncenter(work _buffer,50);
printf("%s\n",w ork_buffer);
strljust(work_b uffer);
printf("%s\n",w ork_buffer);
strrjust(work_b uffer);
printf("%s\n",w ork_buffer);
}

/* Left justify a string */
strljust(str )
char *str;
{
int len;

len = strlen(str);
while (isspace(str) != 0) { %%%%%% should be isspace(*str) - isspace expects a char, not a pointer
to one memmove (str,str + 1,len);
str[len] = ' ';
}
}

/* Reverse a string */
strrev(str) %%%%%% strrev is already defined. choose another namechar *str;
{
char ch;
char *end;

end = str + strlen(str) - 1;

while (str < end) {
ch = *end;
*end-- = *str;
*str++ = ch;
}
}

/* Right justify a string */
strrjust(str )
char *str;
{
strrev(str);
strljust(str);
strrev(str);
}

/* Truncate to last non-white character */
strtrunc(str )
char *str;
{
char *end;

end = str + strlen(str) - 1;

while ((*str != 0) && (isspace (*end) != 0)) {
*end-- = 0;
}
}

/* Pad a string for len with spaces */
struntrunc(str ,len)
char *str;
int len;
{
while (strlen (str) < len) {
strcat (str,' '); %%%%%% should be strcat(str, " "); - strcat() expects two strings }
}

/* Center a string */
strcenter(st r)
char *str;
{
strncenter (str, strlen(str));
}

/* Center a string within width */
strncenter(str ,width)
char *str;
int width;
{
int non_blank_len, padding;

strtrunc (str);
strrev (str);
strtrunc (str);
non_blank_len = strlen (str);

padding = (width - non_blank_len) / 2;

struntrunc (str,padding);
strrev (str);
struntrunc (str,width);
}

It seems to be blowing up in the struntrunc function, but I can't
understand why. I know that this program is trying to take a string,
center it, left justify it and right justify it.

Roberto Waltman

[ Please reply to the group, ]
[ return address is invalid. ]

[pete]

Mike Polinske wrote:

I am new to the C programming language but have been programming in
Cobol for over 10 years. When I compile the following code, it
compiles clean but I get an application error both under Windows XP and
Win2K.

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

char title[] = "Year End Report";

char work_buffer[51];

main()
{
strcpy(work_buf fer,title);
strncenter(work _buffer,50);
printf("%s\n",w ork_buffer);
strljust(work_b uffer);
printf("%s\n",w ork_buffer);
strrjust(work_b uffer);
printf("%s\n",w ork_buffer);
}

/* Left justify a string */
strljust(str)
char *str;
{
int len;

len = strlen(str);
while (isspace(str) != 0) {
memmove (str,str + 1,len);
str[len] = ' ';
}
}

/* Reverse a string */
strrev(str)
char *str;
{
char ch;
char *end;

end = str + strlen(str) - 1;

while (str < end) {
ch = *end;
*end-- = *str;
*str++ = ch;
}
}

/* Right justify a string */
strrjust(str)
char *str;
{
strrev(str);
strljust(str);
strrev(str);
}

/* Truncate to last non-white character */
strtrunc(str)
char *str;
{
char *end;

end = str + strlen(str) - 1;

while ((*str != 0) && (isspace (*end) != 0)) {
*end-- = 0;
}
}

/* Pad a string for len with spaces */
struntrunc(str, len)
char *str;
int len;
{
while (strlen (str) < len) {
strcat (str,' ');
}
}

/* Center a string */
strcenter(str)
char *str;
{
strncenter (str, strlen(str));
}

/* Center a string within width */
strncenter(str, width)
char *str;
int width;
{
int non_blank_len, padding;

strtrunc (str);
strrev (str);
strtrunc (str);
non_blank_len = strlen (str);

padding = (width - non_blank_len) / 2;

struntrunc (str,padding);
strrev (str);
struntrunc (str,width);
}

It seems to be blowing up in the struntrunc function, but I can't
understand why. I know that this program is trying to take a string,
center it, left justify it and right justify it.

Any ideas on how I can get this program to run?

/* BEGIN new.c */

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

void str_ljust(char *str);
void str_rev(char *str);
void str_rjust(char *str, size_t len);
void str_trunc(char *str);
void str_untrunc(cha r *str, size_t len);
void str_center(char *str);
void str_ncenter(cha r *str, size_t len);

int main(void)
{
char title[] = " Year End Report ";
char work_buffer[51];

strcpy(work_buf fer, title);

str_ncenter(wor k_buffer, 50);
printf("%s\n",w ork_buffer);

str_ljust(work_ buffer);
printf("%s\n", work_buffer);

str_rjust(work_ buffer, 50);
printf("%s\n", work_buffer);

return 0;
}

void str_ljust(char *str)
{
char *ptr = str;

while (isspace(*ptr)) {
++ptr;
}
memmove(str, ptr, strlen(ptr) + 1);
}

void str_rev(char *str)
{
char ch;
char *end;

if (str[0] != '\0') {
end = str + strlen(str + 1);
while (str < end) {
ch = *end;
*end-- = *str;
*str++ = ch;
}
}
}

void str_rjust(char *str, size_t len)
{
size_t pad;

str_rev(str);
str_trunc(str);
str_rev(str);
str_trunc(str);
pad = len - strlen(str);
memmove(str + pad, str, strlen(str) + 1);
memset(str, ' ', pad);
}

void str_trunc(char *str)
{
char *end = str + strlen(str);

while (end != str && isspace(*--end)) {
*end = '\0';
}
}

void str_untrunc(cha r *str, size_t len)
{
memset(str + strlen(str), ' ', len - strlen(str));
str[len] = '\0';
}

void str_center(char *str)
{
str_ncenter (str, strlen(str));
}

void str_ncenter(cha r *str, size_t len)
{
size_t pad;

str_rev(str);
str_trunc(str);
str_rev(str);
str_trunc(str);
pad = (len - strlen(str)) / 2;
memmove(str + pad, str, strlen(str) + 1);
memset(str, ' ', pad);
}

/* END new.c */
--
pete

[Mike Polinske]

Thank you everyone!!

I am using a book called "Moving from Cobol to C" by Mo Budlong which
is from 1993.

I thought it would be good to start with this book rather than K&R's C
Programming, but I guess I was wrong :-)

I didn't realize C had changed that much and I had ignored the compiler
warnings about no prototypes. I also thought that since C++ is derived
from C I would start out with C programming.

Coming from the nice "wordiness" of Cobol, C and C++ feel like a bunch
of shorthand or hieroglyphics :-)

I'm going to keep on trying to learn C and C++ since I'd like to expand
my programming language knowledge.

[Flash Gordon]

Mike Polinske wrote:

Thank you everyone!!

I am using a book called "Moving from Cobol to C" by Mo Budlong which
is from 1993.
It looks like that book was out of date even when it was written. The C
standard which introduced prototypes came out in 1989!
I thought it would be good to start with this book rather than K&R's C
Programming, but I guess I was wrong :-)
You were. You would be far better off starting with K&R.
I didn't realize C had changed that much and I had ignored the compiler
warnings about no prototypes.
Never ignore warnings because they almost always indicate that you
really do have a problem.
I also thought that since C++ is derived
from C I would start out with C programming.
Yes, learning C before C++ is reasonable.
Coming from the nice "wordiness" of Cobol, C and C++ feel like a bunch
of shorthand or hieroglyphics :-)

I'm going to keep on trying to learn C and C++ since I'd like to expand
my programming language knowledge.

Just remember that although C++ was derived from C in the early days the
languages have diverged significantly so things which are good style in
C are errors in C++ and vice versa.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[Richard Bos]

Flash Gordon <sp**@flash-gordon.me.uk> wrote:

Mike Polinske wrote:

I didn't realize C had changed that much and I had ignored the compiler
warnings about no prototypes.

Never ignore warnings because they almost always indicate that you
really do have a problem.

But also do note that warnings do not always point out exactly the
problem that the text of the warning seems to indicate. One infamous
warning is the one about "converting integer to pointer without a cast",
which most usually does _not_ indicate that you're missing a cast, but
that you've forgot to #include the required header which would tell the
compiler that there is no integer to convert.

Richard

[Default User]

Flash Gordon wrote:

Mike Polinske wrote:

I also thought that since C++ is derived
from C I would start out with C programming.

Yes, learning C before C++ is reasonable.

The C++ people tend to disagree with this. I would generally agree that
if you only want to learn C++, then start with it. I don't agree with
them that C is a handicap to learning C++, not if one chooses a proper
introductory book for that language.

If you'd like to become at least familiar with both languages, then C
is probably the better starting point, as it's a smaller language.

I'm going to keep on trying to learn C and C++ since I'd like to
expand my programming language knowledge.

Just remember that although C++ was derived from C in the early days
the languages have diverged significantly so things which are good
style in C are errors in C++ and vice versa.

And some things that are good style in C are permissible in C++, but
not the optimal way to do things.
Brian