Unresolved external

[Kenny M]

I am trying to build a program written by a colleague and get an
'unresolved external' error when I run the Borland make utility
(offending function below). Any ideas what's wrong? I am not a c++
programmer so a simple solution would be very welcome.

/*
* strtoko.cpp
*
* Does exactly the same as the standard function "strtok", but
* also rebuilds the original string as it goes, but storing the
* separator which was overwritten with an end-of-string and
restoring
* it on the subsequent entry.
*
* Returns a pointer to the next symbol found, or NULL if end of
string.
*
* s i-o : string to be scanned.
* ct in : string containing all valid separators.
*/

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

char *strtoko( char *s, const char *ct )

{ static char *localp, hold;
char *token;

if ( s != NULL )
localp = s;
else
{ if ( localp == NULL )
{ fprintf( stderr, "\nError in 'strtoko' : Called with NULL
prior " );
fprintf( stderr, "to a call with string for scanning.\n"
);
exit(1);
}
if ( hold == '\0' ) return( NULL );
*localp = hold;
localp++;
}

localp += strspn( localp, ct ); /* skip over any separator
characters */
if ( localp == '\0' ) return( NULL );
token = localp;
localp += strcspn( localp, ct ); /* skip to next separator (or
end-string)*/
hold = *localp;
*localp = '\0';
return( token );
}

 

[Thomas J. Gritzan]

I am trying to build a program written by a colleague and get an
'unresolved external' error when I run the Borland make utility
(offending function below). Any ideas what's wrong? I am not a c++
programmer so a simple solution would be very welcome.

First, this is not a program, it is a function. You would have to
provide a main function that calls the function.
The simplest solution would be to ask your colleague for a main function.

Second, the code compiles with a C compiler, so it actually is C code.
It is C++ code too, but in modern C++ you normally want to use
std::string and friends.

/*
* strtoko.cpp
*
* Does exactly the same as the standard function "strtok", but
* also rebuilds the original string as it goes, but storing the
* separator which was overwritten with an end-of-string and
restoring
* it on the subsequent entry. [...]

char *strtoko( char *s, const char *ct )

{ static char *localp, hold;
char *token;

The function is not reentrant. Since this function is supposed to be a
better strtok, I would at least fix that. Of course the interface
(function signature) would need to be changed for this.

if ( s != NULL )
localp = s;
else
{ if ( localp == NULL )
{ fprintf( stderr, "\nError in 'strtoko' : Called with NULL
prior " );
fprintf( stderr, "to a call with string for scanning.\n"
);
exit(1);

I would ASSERT here (in debug mode), and return NULL otherwise. It is a
programming/logic error, and a library function shouldn't exit() a program.

if ( hold == '\0' ) return( NULL );
*localp = hold;
localp++;
}

localp += strspn( localp, ct ); /* skip over any separator
characters */
if ( localp == '\0' ) return( NULL );

This condition is never true. It should be:

if ( *localp == '\0' ) return( NULL );

Otherwise, it won't find the end of the string sometimes.

 

[Kenny M]

Thanks for pointing this out, Thomas. I have replaced his own strtoko
function with the strtok function in string.h and it seems to compile.

I am trying to build a program written by a colleague and get an
'unresolved external' error when I run the Borland make utility
(offending function below). Any ideas what's wrong? I am not a c++
programmer so a simple solution would be very welcome.

First, this is not a program, it is a function. You would have to
provide a main function that calls the function.
The simplest solution would be to ask your colleague for a main function.

Second, the code compiles with a C compiler, so it actually is C code.
It is C++ code too, but in modern C++ you normally want to use
std::string and friends.

/*
* strtoko.cpp
*
* Does exactly the same as the standard function "strtok", but
* also rebuilds the original string as it goes, but storing the
* separator which was overwritten with an end-of-string and
restoring
* it on the subsequent entry. [...]

char *strtoko( char *s, const char *ct )

{ static char *localp, hold;
char *token;

The function is not reentrant. Since this function is supposed to be a
better strtok, I would at least fix that. Of course the interface
(function signature) would need to be changed for this.

if ( s != NULL )
localp = s;
else
{ if ( localp == NULL )
{ fprintf( stderr, "\nError in 'strtoko' : Called with NULL
prior " );
fprintf( stderr, "to a call with string for scanning.\n"
);
exit(1);

I would ASSERT here (in debug mode), and return NULL otherwise. It is a
programming/logic error, and a library function shouldn't exit() a program.

if ( hold == '\0' ) return( NULL );
*localp = hold;
localp++;
}

localp += strspn( localp, ct ); /* skip over any separator
characters */
if ( localp == '\0' ) return( NULL );

This condition is never true. It should be:

if ( *localp == '\0' ) return( NULL );

Otherwise, it won't find the end of the string sometimes.

token = localp;
localp += strcspn( localp, ct ); /* skip to next separator (or
end-string)*/
hold = *localp;
*localp = '\0';
return( token );
}