A . in a user entered char* crashes it

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August 6th, 2006, 04:05 PM

Rossss

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A "." in a char* crashes it

Hi, i have a very simple problem that im pulling my hair out over!

The user enters a filepath to a char*
It reads data in that file to a structure with ifstream
It then outputs data from the structure to several files with ofstream
When it exits the ofstream loop the program is finished, or it should be
If the file being read is "c:\file" it ends the program no problem
But if the file being read is "c:\file.txt" it crashes between the last loop and the final } used to end the program

In the CPU debug window it stops at "mov ebx,[ebx+0x04]"
when it stops, the ebx register is empty, just shows 00000000

It works fine in the built .exe just not when i run it from borland, but i dont want memory leaks, etc in the final version

I've never had this problem before, it doesnt even seem to make sense

Last edited by Rossss : August 6th, 2006 at 04:25 PM. Reason: extra info

August 6th, 2006, 05:24 PM

Itsacon

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Could you post the source code?

Preferably between [code] or [highlight=C++] tags :-)

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This is my code. Is it not nifty?

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August 6th, 2006, 06:39 PM

Rossss

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Sure, here it is;

C++ Code:

Original - C++ Code

/*
Title:          PageMaker
Description:    Takes a wordlist (path given by user) & creates an
                empty web page for every line in the wordlist.
                Every web page is named from the word read out in the wordlist.
                All entrys in wordlist must be on a seperate line
*/

#include <stdio.h>
#include <fstream.h>

struct word
{
        char newFile[100];
};

void main()
{
        struct word word1[1000];
        char* path;

//----------------------------------------------------------------------
//Get File Path

printf("\nPlease enter the location of your wordlist:  ");
        scanf("%s", path);

char * dirname  = path;
        //char * filename = "wordlist.txt";
        char * tmpdirname;

// Length of new string includes directory
        // separator and null character
        int newlen = strlen(dirname) + 2;
        tmpdirname = (char *) malloc(newlen);
        if (tmpdirname == NULL)
        {
                // Handle memory error.
        }

strcpy(tmpdirname, dirname);

dirname = tmpdirname;

//----------------------------------------------------------------------
// Read File In

ifstream infile(dirname);

if (infile.fail())
        {
                printf("Sorry, input file not available\nEnsure there is a file called %s in the same directory as this program & try again", dirname);
                getchar();
                getchar();
                exit(1);
        }

int i=1;
        while (!infile.eof())
        {

infile.getline(word1[i].newFile, 100);
                printf("%s\n", word1[i].newFile);
                i++;
        }
        infile.close();

//--------------------------------------------------------------------
// Create Files From 'word' Struct

//Every loop cycle creates a new file from that particular
        //structure entry, and appends '.html' to the filename
        for (int j=1; j != i; j++)
        {

string tempword2 = word1[j].newFile;

char* outfilename = word1[j].newFile;
                outfilename = strcat(outfilename, ".html");

ofstream outfile(outfilename);
                if (outfile.fail())
                {
                        printf("Unknown Output Error\nProgram will now end\n");
                        getchar();
                        getchar();
                        exit(1);
                }

//HTML Head
        outfile << "<html><head>";
        outfile << "<title>" << outfile << "</title>";
        outfile << "<meta name=\"keywords\" content=\"\" >";
        outfile << "<meta name=\"description\" content=\"\" >";
        outfile << "</head>";

//HTML Body
        outfile << "<body>test line - working?";
        outfile << "</body></html>";

//Close outfile
        outfile.close();

}

printf("\n\n\nTask Completed!");
        getchar();
        getchar();
}

/*
Title:          PageMaker
Description:    Takes a wordlist (path given by user) & creates an
                empty web page for every line in the wordlist.
                Every web page is named from the word read out in the wordlist.
                All entrys in wordlist must be on a seperate line
*/
 
#include <stdio.h>
#include <fstream.h>
 
struct word
{
        char newFile[100];
};
 
void main()
{
        struct word word1[1000];
        char* path;
 
//----------------------------------------------------------------------
//Get File Path
 
        printf("\nPlease enter the location of your wordlist:  ");
        scanf("%s", path);
 
        char * dirname  = path;
        //char * filename = "wordlist.txt";
        char * tmpdirname;
 
 
        // Length of new string includes directory
        // separator and null character
        int newlen = strlen(dirname) + 2;
        tmpdirname = (char *) malloc(newlen);
        if (tmpdirname == NULL)
        {
                // Handle memory error.
        }
 
        strcpy(tmpdirname, dirname);
 
        dirname = tmpdirname;
 
//----------------------------------------------------------------------
// Read File In
 
        ifstream infile(dirname);
 
        if (infile.fail())
        {
                printf("Sorry, input file not available\nEnsure there is a file called %s in the same directory as this program & try again", dirname);
                getchar();
                getchar();
                exit(1);
        }
 
        int i=1;
        while (!infile.eof())
        {
 
                infile.getline(word1[i].newFile, 100);
                printf("%s\n", word1[i].newFile);
                i++;
        }
        infile.close();
 
//--------------------------------------------------------------------
// Create Files From 'word' Struct
 
        //Every loop cycle creates a new file from that particular
        //structure entry, and appends '.html' to the filename
        for (int j=1; j != i; j++)
        {
 
                string tempword2 = word1[j].newFile;
 
 
                char* outfilename = word1[j].newFile;
                outfilename = strcat(outfilename, ".html");
 
                ofstream outfile(outfilename);
                if (outfile.fail())
                {
                        printf("Unknown Output Error\nProgram will now end\n");
                        getchar();
                        getchar();
                        exit(1);
                }
 
        //HTML Head
        outfile << "<html><head>";
        outfile << "<title>" << outfile << "</title>";
        outfile << "<meta name=\"keywords\" content=\"\" >";
        outfile << "<meta name=\"description\" content=\"\" >";
        outfile << "</head>";
 
        //HTML Body
        outfile << "<body>test line - working?";
        outfile << "</body></html>";
 
        //Close outfile
        outfile.close();
 
        }
 
        printf("\n\n\nTask Completed!");
        getchar();
        getchar();
}

August 7th, 2006, 01:45 AM

Itsacon

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Ah, problem found.

You can't just write a string to an uninitialized pointer!.

Either declare it as

Code:

char[256] path;

or put a

Code:

char = malloc(256 * sizeof(char));

before the scanf.

It's a wonder your system hasn't BSOD'ed, you're writing the string to a completely random place in memory!

Comments on this post

ubergeek agrees: as long as you meant char path[256];

August 7th, 2006, 12:36 PM

ubergeek

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correction:

char path[256];
path = malloc(256 * sizeof(char));

August 7th, 2006, 01:37 PM

Itsacon

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Quote:

Originally Posted by ubergeek

correction:

char path[256];
path = malloc(256 * sizeof(char));

Oops, you're right. Turned those around...

That's what you get for posting in a rush, thanks for correcting me.

August 7th, 2006, 03:00 PM

Rossss

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Excellent!
Thanks guys it works a treat, i thought it had to be some small silly thing i'd done, duh!

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