insert linked list - segment violation

This is a discussion on insert linked list - segment violation within the C Programming forums, part of the General Programming Boards category; what is wrong with this function? This function insert a new node in the linked list, but it'not works. Code: ...

  1. #1
    Registered User
    Join Date
    Dec 2007
    Posts
    25

    insert linked list - segment violation

    what is wrong with this function? This function insert a new node in the linked list, but it'not works.

    Code:
    void insertFrontierAstar ( FrontierNodePtr *headPtr, TreeNodePtr ptr )
    {
    	FrontierNodePtr currentPtr, previousPtr;
    	
    	FrontierNodePtr newPtr;
    
    	newPtr = malloc ( sizeof ( FrontierNode ) );
    
    	if ( newPtr == NULL )                            
    	{
    		printf( "can't allocate memory for FrontierNodePtr\nexit program\n" );
    		exit ( 3 );
    	}
    
    	else
    	{
    		newPtr->leaf = ptr;
    		newPtr->next = NULL;
    
    		previousPtr = NULL;
    		currentPtr = *headPtr;
    
    		while ( currentPtr != NULL && currentPtr->leaf->sum < newPtr->leaf->sum )
    		{
    			previousPtr = currentPtr;
    			currentPtr = currentPtr->next;
    		}
    
    		if ( previousPtr == NULL )
    		{
    			newPtr->next = *headPtr;
    			*headPtr = newPtr;
    			return;
    		}
    
    		if ( currentPtr->leaf->sum > newPtr->leaf->sum )
    		{
    			previousPtr->next = newPtr;
    			newPtr->next = currentPtr;
    		}
    
    		if ( currentPtr->leaf->sum == newPtr->leaf->sum )
    		{
    			while ( currentPtr->leaf->g >= newPtr->leaf->g )
    			{
    				previousPtr = currentPtr;
    				currentPtr = currentPtr->next;
    			}
    
    			previousPtr->next = newPtr;
    			newPtr->next = currentPtr;
    
    		}
    
    
    
    
    
    	}
    
    
    
    }
    thank you in advance
    Code:
    # define EVERYTHINK 0
    int main ( void )
    { 
       while ( C_learning )
                 english_learning ( );
       return EVERYTHINK;
    }

  2. #2
    Kernel hacker
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    Farncombe, Surrey, England
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    Code:
    		if ( currentPtr->leaf->sum > newPtr->leaf->sum )
    		{
    			previousPtr->next = newPtr;
    			newPtr->next = currentPtr;
    		}
    
    		if ( currentPtr->leaf->sum == newPtr->leaf->sum )
    		{
    			while ( currentPtr->leaf->g >= newPtr->leaf->g )
    			{
    				previousPtr = currentPtr;
    				currentPtr = currentPtr->next;
    			}
    
    			previousPtr->next = newPtr;
    			newPtr->next = currentPtr;
    
    		}
    This section can be entered with currentPtr == NULL - which will cause segmentation fault, of course.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Registered User
    Join Date
    Dec 2007
    Posts
    25
    thank You Mats, for quick response. I' will check it
    Code:
    # define EVERYTHINK 0
    int main ( void )
    { 
       while ( C_learning )
                 english_learning ( );
       return EVERYTHINK;
    }

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
    Join Date
    Oct 2007
    Posts
    22,172
    Before dereferencing any pointers, be sure to check them for NULL!
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
    For information on how to enable C++11 on your compiler, look here.
    よく聞くがいい!私は天才だからね! ^_^

  5. #5
    Registered User
    Join Date
    Dec 2007
    Posts
    25
    well, i learn my lesson, thank you Mats (again) and Elysia, you are the best,
    here is my function, completed and running.

    Code:
    void insertFrontierAstar ( FrontierNodePtr *headPtr, FrontierNodePtr *tailPtr, TreeNodePtr ptr )
    {
    	FrontierNodePtr currentPtr, previousPtr;  
    	FrontierNodePtr newPtr;
    
    	newPtr = malloc ( sizeof ( FrontierNode ) );
    
    	if ( newPtr == NULL )                             
    	{
    		printf( "can't allocate memory for FrontierNodePtr\nexit program\n" );
    		exit ( 3 );
    	}
    
    	else
    	{
    		newPtr->leaf = ptr;
    		newPtr->next = NULL;
    
    		if ( *headPtr == NULL )
    		{
    			newPtr->next = *headPtr;
    			*headPtr = newPtr;
    		}
    
    		else
    		{
    			previousPtr = NULL;
    			currentPtr = *headPtr;
    
    			if ( currentPtr->leaf->sum > newPtr->leaf->sum )
    			{
    				newPtr->next = *headPtr;
    				*headPtr = newPtr;
    			}
    
    			else if ( currentPtr->leaf->sum < newPtr->leaf->sum )
    			{
    				while ( currentPtr != NULL && currentPtr->leaf->sum < newPtr->leaf->sum )
    				{
    					previousPtr = currentPtr;
    					currentPtr = currentPtr->next;
    				}
    
    				if ( currentPtr == NULL )
    				{
    					( *tailPtr )->next = newPtr;
    					*tailPtr = newPtr;
    				}
    
    				else if ( currentPtr != NULL && currentPtr->leaf->sum > newPtr->leaf->sum )
    				{
    					previousPtr->next = newPtr;
    					newPtr->next = currentPtr;
    				}
    
    				else if ( currentPtr != NULL && currentPtr->leaf->sum == newPtr->leaf->sum )
    				{
    					while ( currentPtr != NULL && currentPtr->leaf->sum == newPtr->leaf->sum
    							&& currentPtr->leaf->g >= newPtr->leaf->g )
    					{
    						previousPtr = currentPtr;
    						currentPtr = currentPtr->next;
    					}
    
    					if ( currentPtr == NULL )
    					{
    						( *tailPtr )->next = newPtr;
    						*tailPtr = newPtr;
    					}
    
    					else
    					{
    						previousPtr->next = newPtr;
    						newPtr->next = currentPtr;
    					}
    				}
    			}
    
    			else
    			{
    				while ( currentPtr != NULL && currentPtr->leaf->sum == newPtr->leaf->sum
    							&& currentPtr->leaf->g >= newPtr->leaf->g )
    				{
    					previousPtr = currentPtr;
    					currentPtr = currentPtr->next;
    				}
    
    				if ( currentPtr == NULL )
    				{
    					( *tailPtr )->next = newPtr;
    					*tailPtr = newPtr;
    				}
    
    				else if ( previousPtr == NULL )
    				{
    					newPtr->next = *headPtr;
    					*headPtr = newPtr;
    				}
    
    				else
    				{
    					previousPtr->next = newPtr;
    					newPtr->next = currentPtr;
    				}
    			}
    		}
    
    	}
    
    
    
    }
    Code:
    # define EVERYTHINK 0
    int main ( void )
    { 
       while ( C_learning )
                 english_learning ( );
       return EVERYTHINK;
    }

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