Thread: I can't fix this c code! Who can??

Greetings.

Am in dire need of help here. I have been building a certain system which is part of an RPC/PHP extension that creates memory-based matrices for certain data analysis purposes. Am not good in memory management code, I must admit in advance. And hence, am currently stuck in a notorious C's memory miry clay - for sure! All sorts of memory errors and bugs have plagued me for a while now. I need urgent help to finish this application within a few weeks.

I have recreated, in the following much lesser code (below), to simulate the senario within the other code that seems to be the culprit. After compiling, with Intel C++ Compiler 9.1 or MS Studio 2003, I get the same type of access violation errors of all sorts, including: -
"The thread 'Win32 Thread' (0x1520) has exited with code 0 (0x0).
Unhandled exception at 0x7c910ef4 in WIN32ConsoleApp.exe: 0xC0000005: Access violation reading location 0xfffffff8."

Where am I going wrong??? I can't seem to overcome this bug. I have to stick to C - no matter the rugged edges and bleeding corners. SOMEBODY HELP!!!

Code:

/* RECEIVE CONSOLE INPUT AND CREATE A MOCK REPRESENTATION MATRIX */ 
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define EQL == /* Equal To */
#define NEQL != /* Not Equal To */
#define LOEQL <= /* Less Than or Equal To */
#define GOEQL >= /* Greater Than or Equal To */

typedef unsigned int uint;
typedef signed int sint;

#define e 2.718281828
#define ROWS 5
#define COLS 5
#define MAX_INPUT_LEN 254

void deallocate2D(double **array, int nrows) {

	/*  deallocate each row  */
	int i;
	for(i = 0; i < nrows; i++) {
		free(array[i]);
		array[i]=NULL;
	}
	/*  deallocate array of pointers  */
	free(array);
	array=NULL;
}

void deallocate2C(char **array, int nrows) {

	/*  deallocate each row  */
	int i;
	for(i = 0; i < nrows; i++) {
		free(array[i]);
		array[i]=NULL;
	}
	/*  deallocate array of pointers  */
	free(array);
	array=NULL;
}

void quitapp(uint rowcnt,double **mem2Dblock_a,char **mem2Dblock_b)
{
	deallocate2D(mem2Dblock_a,rowcnt);
	deallocate2C(mem2Dblock_b,rowcnt);
	fcloseall();
	fprintf(stderr,"\nCleaned up.\nExiting.\nBye!");
	exit(0);
}

void restartapp(char *appexec,uint rowcnt,double **mem2Dblock_a,char **mem2Dblock_b)
{
	deallocate2D(mem2Dblock_a,rowcnt);
	deallocate2C(mem2Dblock_b,rowcnt);
	fcloseall();
	system(appexec);
	exit(0);
}

int main(int argc,char *argv[])
{ 
	static uint i=0,j=0,k=0,m=0,n=0,lastknown_rows=0,lastknown_cols=0,lastknown_dims=0,outputlen=0,ramgrowth=0;
	size_t inputlen;
	char **kylst=malloc(sizeof(char*)*1);
	double **kbmtx=malloc(sizeof(double*)*1);
	char buff[MAX_INPUT_LEN];

	char *dimfilenm = "~dim.tmp";
	char *kyfilenm = "~ky.lst";
	char *kbfilenm = "~kb.bin";
	char *outfilenm = "~out.tmp";
	FILE *kbfile=NULL;
	FILE *dimfile=NULL;
	FILE *kyfile=NULL;
	FILE *outfile=NULL;

	if(argc==2)
	{
		if(((dimfile=fopen(dimfilenm, "r")) NEQL NULL) && (lastknown_dims=fscanf(dimfile,"%d %d",&lastknown_rows,&lastknown_cols))EQL 2)
		{
			m=lastknown_rows;
			n=lastknown_cols;
			printf("/* Found a valid DIM file showing %dx%d to be the last known dimensions */\n",m,n);
			printf("/* Locate and try reading the stored KY list file */\n");
			if((kyfile = fopen(kyfilenm, "r")) EQL NULL) 
			{ 
				m=0;
				n=0;
				if((kyfile = fopen(kyfilenm, "w")) NEQL NULL) 
				{ 
					printf("/* Created a new KY list file */\n");
					//restartapp(argv[0],m,kbmtx,kylst); 
					if((kbfile = fopen(kbfilenm, "wb")) NEQL NULL) 
					{ 
						printf("/* Created a new KB list file */\n");
						//restartapp(argv[0],m,kbmtx,kylst); 
						printf("/* Please restart %s to proceed */\n",argv[0]);
						fprintf(dimfile,"%d %d\n",m,n);
						quitapp(m,kbmtx,kylst);
					}  else {
						fprintf(stderr, "/* Error creating a new KB list file */\n");
						quitapp(m,kbmtx,kylst);
					}
				}  else { /* if((kyfile = fopen(kyfilenm, "w")) NEQL NULL) */
					fprintf(stderr, "/* Error creating a new KY list file */\n");
					quitapp(m,kbmtx,kylst);
				}				
				fclose(kbfile);
			} else { /* if((kyfile = fopen(kyfilenm, "r")) EQL NULL) */
				if(m>0&&n>0)
				{
					m=lastknown_rows;
					n=lastknown_cols;
					printf("/* Resize 'char** kylst' to accommodate the last known rows : %d */\n",m);
					kylst=(char**)realloc(kylst,(size_t)(sizeof(char*)*(m)));
					if(kylst EQL NULL)quitapp(m,kbmtx,kylst);	
					k=0;
					for(i=0;i<(m);i++)
					{
						k+=fscanf(kyfile,"%s",buff);
						if(i > k) {i--; break;}
						if((kylst[i] = (char *)malloc((size_t)((strlen(buff)+1)*sizeof(char)))) EQL NULL)quitapp(m,kbmtx,kylst);
						strcpy(kylst[i],buff);
					}
					printf("/* Locate and try reading the stored KB data file */\n");
					if((kbfile = fopen(kbfilenm, "rb")) NEQL NULL) 
					{ 
						printf("/* Resize 'double **kbmtx' to accommodate the last known dimensions : %dx%d */\n",m,n);
						kbmtx=(double**)realloc(kbmtx,sizeof(double*)*m);
						if(kbmtx==NULL)quitapp(m,kbmtx,kylst);
						printf("/* Initialize KB with zeros. */\n");
						for(i = 0; i < m; i++) 
						{
							kbmtx[i]=(double*)malloc(sizeof(double)*n);
							if(kbmtx[i]==NULL) quitapp(m,kbmtx,kylst);
							for(j = 0; j < n; j++)
							{
								kbmtx[i][j]=0.0;
								printf("%lg\t",kbmtx[i][j]);
							}
							printf("\n");		
						}
						printf("/* Load the binary file data into KB, row by row. */\n");
						for (i = 0; i < m; i++) 
						{
							if (fread(kbmtx[i], sizeof(double), n, kbfile) != n) 
							{ 
								fprintf(stderr, "Error writing to file."); 
								quitapp(m,kbmtx,kylst);
							} 
						}

						printf("/* Close the binary file */\n");
						fclose(kbfile);

						printf("/* Now print KB to the screen. */\n");
						for (i = 0; i < m; i++) 
						{
							for(j = 0; j < n; j++)
							{
								printf("%lg\t",kbmtx[i][j]);
							}
							printf("\n");
						}
						printf("/* Show KB RAM addresses on the screen. */\n");
						for (i = 0; i < m; i++) 
						{
							for(j = 0; j < n; j++)
							{
								printf("%d\t",&kbmtx[i][j]);
							}
							printf("\n");
						}
					}  else { /* if((kbfile = fopen(kbfilenm, "rb")) NEQL NULL) */
						fprintf(stderr, "/* Cannot read the KB data file */\n");
						quitapp(m,kbmtx,kylst);
					}
				}
				fclose(kyfile);
			}
			fclose(dimfile);
			puts("Type A New String and Press <ENTER> To Store in RAM and Binary File, ");
			for(m=lastknown_rows,n=lastknown_cols;;m++,n++)
			{
				if((dimfile = fopen(dimfilenm, "w")) NEQL NULL)
				{					
					gets(buff);
					inputlen=(strlen(buff)+1);
					if(inputlen<MAX_INPUT_LEN)
					{
						if(strcmp(buff,"Q!") EQL 0)
						{
							quitapp(m,kbmtx,kylst);
						}
						if((kyfile = fopen(kyfilenm, "a")) NEQL NULL)
						{
							kylst=(char**)realloc(kylst,(size_t)(sizeof(char*)*(m+1)));
							if(kylst EQL NULL)quitapp(m,kbmtx,kylst);
							kylst[m]=(char*)malloc((size_t)(sizeof(char)*inputlen));
							if(kylst[m] EQL NULL)quitapp(m,kbmtx,kylst);
							strcpy(kylst[m],buff);
							if((kbmtx=(double **)realloc(kbmtx,(size_t)((m+1)*sizeof(double*)))) NEQL NULL)
							{
								if((kbmtx[m]=(double *)malloc((size_t)((n+1)*sizeof(double)))) EQL NULL)quitapp(m,kbmtx,kylst);
								for(i=0;i<(m+1);i++)
								{
									for(j=0;j<(n+1);j++)
									{
										kbmtx[i][j]=0.0;
									}
								}
							} else quitapp(m,kbmtx,kylst);
							printf("Committing to KY list file\n");
							fprintf(kyfile,"%s\n",kylst[m]);
							printf("/* Opening the KB binary data file for writing */\n");
							if((kbfile = fopen(kbfilenm, "wb")) NEQL NULL) 
							{ 
								for(i=0;i<(m+1);i++)
								{
									if((fwrite(kbmtx[i],sizeof(double),(n+1),kbfile))!=(n+1))quitapp(m,kbmtx,kylst);
								}	
								fclose(kbfile);
							} else {
								fprintf(stderr, "Error opening KB file for updates."); 
								quitapp(m,kbmtx,kylst); 
							}						
							fclose(kyfile);
							fprintf(dimfile,"%d %d\n",m+1,n+1);
							//lastknown_dims=flushall();					
							//printf("/* Written %d updates to DIM file */\n",lastknown_dims);							
							printf("/* Show KB RAM addresses on the screen. */\n");
							for (i = 0; i < (m+1); i++) 
							{
								for(j = 0; j < (n+1); j++)
								{
									printf("%lg\t",kbmtx[i][j]);
								}
								printf("\n");
							}
							puts("Type and Store Another String Or Type Q! and <ENTER> To Quit: ");
						} else printf("/* Oops! Cannot open KY list file for updates */\n");
					} else { /* if(buff<MAX_INPUT_LEN) */
						printf("/* Oops! Your input is too large. Keep it below 254 characters */\n");
					}						
				}  else printf("/* Oops! Cannot open DIM file for updates */\n");
				fclose(dimfile);
			}
		} else { /* if(((dimfile=fopen(dimfilenm, "r+")) NEQL NULL) && (lastknown_dims=fscanf(dimfile,"%d %d",&lastknown_rows,&lastknown_cols))EQL 2) */
			fprintf(stderr, "/* Cannot read or verify integrity of the DIM file */\n");
			if((dimfile = fopen(dimfilenm, "w")) NEQL NULL) 
			{ 
				printf("/* Created a new DIM file */\n"); 
				fprintf(dimfile,"%d %d\n",0,0);
				printf("/* Please restart %s to proceed */\n",argv[0]);
				quitapp(m,kbmtx,kylst);
			}  else {
				fprintf(stderr, "/* Error creating a new DIM file */\n");
				quitapp(m,kbmtx,kylst);
			}
		}
		quitapp(m,kbmtx,kylst);
	}

	return(0); 
}

Hi Matsp. Much appreciated your quick rescue response. Thanks man, you were first.

Concerning...
Debugger? Yes, I have tried the VS 2003 Debugger, Intel C++ Debugger and WinDbg to no much avail.

I agree with you though for pointing out quite possibly where the bug might be coming from - some NULL pointer somewhere, or some NULL misuse. If that be so, I have gotten there for following 'sound' advice all over the net as to how 'best' to free heap'd memory by NULLing the pointer after free'ing it. I probably have abused otherwise good practice. I'll check out for my error.

Concering...

Code:

#define EQL == /* Equal To */
#define NEQL != /* Not Equal To */
#define LOEQL <= /* Less Than or Equal To */
#define GOEQL >= /* Greater Than or Equal To */

...I must say, in my humble opinion, this has saved me a lot of times in avoiding major typos bugs, like assignments (=) when I needed comparison (==), for instance. This approach, is actually well recommended in books like Deep C. So I type...

Code:

if((c EQL d)&&(c NEQL e)){}

. It has worked well for me, but thanks for asking.

Concerning...
"restartapp", that is redundant code (probably invalid too), I have never used that piece of code, please ignore it. I doubt it would even work in the first place.

Thanks again.

Still worried though.

Your program contains a number of distinct sections. Some of which seem to be mutually exclusice in a run (in particular A A' and B B'). If you replace the the //SECTION commments with print statements, you could further narrow down the problem and you could get more help. This is a big piece of code you posted, so you might get faster help if you also post all input files and a what you're inputting at the keyboard. In short, a step by step process to reproduce the problem.

Code:

if(((dimfile=fopen(dimfilenm, "r")) NEQL NULL) && (lastknown_dims=fscanf(dimfile,"%d %d",&lastknown_rows,&lastknown_cols))EQL 2)
    {
        // SECTION A
        m=lastknown_rows;
        n=lastknown_cols;
        printf("/* Found a valid DIM file showing %dx%d to be the last known dimensions */\n",m,n);
        printf("/* Locate and try reading the stored KY list file */\n");
        if((kyfile = fopen(kyfilenm, "r")) EQL NULL) 
        { 
            // SECTION B
        } 
        else 
        { 
            // SECTION B'
            if(m>0&&n>0)
            {
                // SECTION C
            }
            fclose(kyfile);
        }

        fclose(dimfile);
        puts("Type A New String and Press <ENTER> To Store in RAM and Binary File, ");

        for(m=lastknown_rows,n=lastknown_cols;;m++,n++)
        {
            if((dimfile = fopen(dimfilenm, "w")) NEQL NULL)
            {                    
                // SECTION D
                } else { /* if(buff<MAX_INPUT_LEN) */
                    printf("/* Oops! Your input is too large. Keep it below 254 characters */\n");
                }                        
            }  else printf("/* Oops! Cannot open DIM file for updates */\n");
            fclose(dimfile);
        }
    }
     else 
    {
        // SECTION A'
    }

Deendee, I fixed the bug in your code. You owe me some beer!

I just had to say that I loved the "shooting yourself in the foot" analogy

Thanks dude for following thru.

I found out what was wrong with my code myself, only I didn't publish soon enough. The bug was in the looping of malloc (after the realloc) without first initializing the looped pointer kbmtx[i]. So I fixed that by just initializing the pointer to a NULL; That fixed my mock-code and the production app-code is running great now.

All the other commissions and/or omissions pointed out before, have been considered and action taken - where necessary. Like I said before, the production code is far cleaner and neater than this concept test code published above.

I thank God and all who helped me think hard. Let's keep c'ing on this forum and keep this lang going, it gives power to the programmer - and yes you can shoot urself in the foot too!

But I still like it, much!

Cheers!

|;-)