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NNTP-Posting-Date: Sat, 04 Aug 2012 11:27:34 -0500
Message-ID: <501D4D74.F6C@mindspring.com>
Date: Sat, 04 Aug 2012 12:27:32 -0400
From: pete <pfiland@mindspring.com>
Reply-To: pfiland@mindspring.com
Organization: PF
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Subject: Re: Trying to figure out how to dynamically re-allocate strings while concatenating
References: <eb47af15-f8ff-4737-983d-3f54307c1081@googlegroups.com> <check-20120804172635@ram.dialup.fu-berlin.de>
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Xref: csiph.com comp.lang.c:24213

Stefan Ram wrote:
> 
> Shriramana Sharma <jamadagni@gmail.com> writes:
> >Can anyone kindly point me to what I am doing wrong with realloc?
> 
>   The result of an attempt should always be checked according
>   to me. The »free« below is not really required for this
>   small program, but would be helpful in many cases, where the
>   code is repeatedly executed in a program.
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> 
> char * strapp( char * * const a, char const * const b )
> { *a = realloc( *a, 1 + strlen( *a )+ strlen( b ));
>   if( *a )strcat( *a, b );
>   return *a; }
> 
> int main( void )
> { char const * const name_ = "my name is";
>   char * name = malloc( strlen( name_ )+ 1 );
>   if( name )
>   { strcpy( name, name_ );
>     if( strapp( &name, " this or " ))
>     if( strapp( &name, "that." ))
>     printf( "%s\n", name );
>     free( name ); }}

I see from your call to the free function,
that you intend to free the allocated memory within main.

If either call to strapp returns a null pointer,
then your call to free, will free a null pointer instead.

-- 
pete