error C2065: 'NULL'

This is a discussion on error C2065: 'NULL' within the C Programming forums, part of the General Programming Boards category; I'm using Visual Studio 2005 on Windows XP. I'm trying to compile a C program. I'm down to one error. ...

  1. #1
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    error C2065: 'NULL'

    I'm using Visual Studio 2005 on Windows XP. I'm trying to compile a C program. I'm down to one error. When I try to compile the following, I get the error:

    initmol.c(20) : error C2065: 'NULL' : undeclared identifier

    Here's the code. It errors out on the IF statement:


    Code:
    #include <malloc.h>
    #include "molecule.h"
    
    MOLECULE *InitMol( void )
    {
       MOLECULE *m;
        
     
       if ( (m = (MOLECULE *)malloc( sizeof( *m ) )) == NULL ) {
          return( NULL );
       }
    
       m->N_Hydro = -1;
       m->N_Atoms =  0;
       m->N_Bonds =  0;
       m->N_Comps =  0;
       return( m );
    }

  2. #2
    Code Goddess Prelude's Avatar
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    malloc.h is archaic. Use stdlib.h instead. You also don't need to cast the return of malloc.
    My best code is written with the delete key.

  3. #3
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    Thanks Prelude,

    That solved the problem:

    new code:
    Code:
    #include <stdlib.h>
    #include "molecule.h"
    
    MOLECULE *InitMol( void )
    {
       MOLECULE *m;
      
       if ( (m = (MOLECULE *) sizeof( *m ) ) == NULL ) {
    	  return( NULL );
       }
    
       m->N_Hydro = -1;
       m->N_Atoms =  0;
       m->N_Bonds =  0;
       m->N_Comps =  0;
       return( m );
    }

  4. #4
    and the hat of wrongness Salem's Avatar
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    > if ( (m = (MOLECULE *) sizeof( *m ) ) == NULL )
    http://faq.cprogramming.com/cgi-bin/...&id=1043284351
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  5. #5
    Frequently Quite Prolix dwks's Avatar
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    Code:
    if ( (m = (MOLECULE *) sizeof( *m ) ) == NULL ) {
    Presumably you meant
    Code:
    if ( (m = (MOLECULE *)malloc( sizeof( *m ) )) == NULL ) {
    in which case you should read the FAQ and then change it to this:
    Code:
    if ( (m = malloc( sizeof( *m ) )) == NULL ) {
    dwk

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