error in 2 consecutive assignments

Hi there,

within an extensive code that I am developing I obtained a very strange behavior from the code itself, and I cannot figure out what it it that is not done correctly.
Specifically (code reported down here), I allocate certain arrays (2d and 1d) dynamically with standard dynamic allocation using malloc, and right after I assign them with the corresponding values.

The problem here comes from the first assignment of the 2D arrat "vars2[][]" through the 1D array rh_vals[] assigned elsewhere. With the first assignment within a "while loop" I verify the correctness of it by printing the "vars2[][]" and all is right, however, once I exit the while loop and I printf again "vars2[][]", here it is when I do not get the same array.

I hope someone can help although the sample code may seem large
best
CFD

Code:

	
	int i,j,k;
	
	int *dims;
	int *vardims;

	static char varname[NC_MAX_NAME+1];
	const char **varnames2;	//array of pointers to chars
	
	float *rh_vals; //vector
	float **vars2;  //matrix
			
	int lonlength, latlength;	//constants
	
	lonlength  = 64;
	latlength = 512;
	nvars = 126;
	
	
    	// Dynamic allocation of the arrays to pointers char **varnames and float **vars;
    	// This line only allocates the number of entries but NOT the length of the entries:
    	
	varnames2 = (const char**) malloc(1* sizeof(char));
	varnames2[0] = (const char*) malloc( 12 * sizeof(char));
	
	rh_vals = (float*) malloc( latlength*lonlength * sizeof(float));
    	
    	vars2 = (float**) malloc(1* sizeof(float));
	vars2[0] = (float*) malloc( latlength*lonlength * sizeof(float));
    		
	strncpy(varnames2[0], "T", 1);
	
        //WHILE LOOP starts HERE		
    	n = 0;
	while(n < nvars){

	rh_val[n] = dumb_function(rh_val); //This function to find rh_vals isn't reported
	varname = dumb_function(varname); //This function to assign varname isn't reported
			
	strncpy(varnames2[n], varname, sizeof(varname));
			
	          if( strncmp(varnames2[n],"T",1) == 1){
				
			k=0;
			for(i=0; i<lonlength; i++){
				for(j=0; j<latlength; j++){
						
					vars2[0][k] = rh_vals[k];
					
                                  	//FIRST PRINT TO CHECK VARS2
					printf("k=%d  rhvals[%d]: %f\n",k, k,vars2[0][k]);
					
                                        k++;
			      }//end for j
		       }//end for i
		}end if
		
	n++;
	}//END OF WHILE LOOP HERE.
		
	
        //ERROR HERE!!!!
	for(k=0; k<=latlength*lonlength; k++){
		if(vars2[0][k] != 0.0)
		//SECOND PRINT TO CHECK VARS2
		printf("k=%d  rhvals[%d]: %f\n",k, k,vars2[0][k]);
	}
		
	
  	//FREE DYN MEMORY:
	free(vars2);
	free(rh_vals);
	free(varnames2);

Code:

    	vars2 = (float**) malloc(1* sizeof(float));

should be

Code:

    	vars2 = (float**) malloc(1* sizeof(float *));

If this is a 64-bit machine, it will make a difference.


Same applies to:

Code:

	varnames2 = (const char**) malloc(1* sizeof(char));

--
Mats

Code:

for(k=0; k<=latlength*lonlength; k++)

should be

Code:

for(k=0; k < latlength*lonlength; k++)

I am a but confused here. Are you trying to do something like this

Code:

varnames2 = (const char**) malloc(1* sizeof(char));
varnames2[0] = (const char*) malloc( 12 * sizeof(char));

if( ( varnames2 = (const char**) malloc(12 * sizeof(char * ) ) ) != NULL )
    for( i=0; i < 12; i++ )
         if( ( varnames2[i] = (const char*) malloc( 12 ) ) != NULL )
         { }

and

Code:

free(vars2);
free(rh_vals);
free(varnames2);

you just can free like this. This will result in a memeory leak. Try using the valgrind tool (assuming that your on Unix platform). Thats would give you more information. You better sweapup properly before you leave mean. Or you end up lots of memory leak. As you mentioned that you working on a large amount of code. Doing this will avoid lots of problems in the futhure.

-ssharish

Originally Posted by matsp

Code:

    	vars2 = (float**) malloc(1* sizeof(float));

should be

Code:

    	vars2 = (float**) malloc(1* sizeof(float *));

If this is a 64-bit machine, it will make a difference.


Same applies to:

Code:

	varnames2 = (const char**) malloc(1* sizeof(char));

--
Mats

Hi Mat, thanks for helping< it is a 64/bit machine,
thank you

Originally Posted by itCbitC

Code:

for(k=0; k<=latlength*lonlength; k++)

should be

Code:

for(k=0; k < latlength*lonlength; k++)

Hi there, thanks for the hint;
cfd

Originally Posted by ssharish2005

I am a but confused here. Are you trying to do something like this

Code:

varnames2 = (const char**) malloc(1* sizeof(char));
varnames2[0] = (const char*) malloc( 12 * sizeof(char));

if( ( varnames2 = (const char**) malloc(12 * sizeof(char * ) ) ) != NULL )
    for( i=0; i < 12; i++ )
         if( ( varnames2[i] = (const char*) malloc( 12 ) ) != NULL )
         { }

and

Code:

free(vars2);
free(rh_vals);
free(varnames2);

you just can free like this. This will result in a memeory leak. Try using the valgrind tool (assuming that your on Unix platform). Thats would give you more information. You better sweapup properly before you leave mean. Or you end up lots of memory leak. As you mentioned that you working on a large amount of code. Doing this will avoid lots of problems in the futhure.

-ssharish

Hi Sharish,
thank you for replying

Is the first part of the code that you suggested the way to allocate memory for an array of pointers?
Also, if free(vars2) etc. is not the correct way to free, should I do it within a loop? something like:

Code:

for( i=0; i < 12; i++ )
    free( varnames2[i])

?

thank you again

Hi everyone who helped. it all works fine now
thank you very much!

cdf