Continued issues with Winows Errors when running program

Printable View

11-12-2006
hpteenagewizkid

Continued issues with Winows Errors when running program

Hello. I'm continuing to get 'myprogram has encountered an error and needs to close' windowsmessages when trying to run any of my programs compiled in C. The current one is this:

Code:

/* References: C by Example C in a Nutshell C Primer 5th Edition Stanford CS Guide to Linked Lists C Reference Library (Functions) */ #include <stdio.h> #include <string.h> #include <stdlib.h> #include <ctype.h> typedef struct filelist { int val; char words[1024]; struct filetext *next; } filetext_t; // Create a structure to hold words and frequency, with sub-structure or next pointer filetext_t *AddToList ( filetext_t *head, char val2[] ) { // Function, create holder for current word filetext_t *current = NULL; // Set an initialising pointer set to NULL if ( head == NULL ) { head = malloc ( sizeof *head ); head->next = NULL; } // If head pointer is NULL, free memory and link to next pointer else { current = malloc ( sizeof *current->next ); current->next = head; head = current; } // Otherwise first node is created so create next node strcpy ( head->words, val2 ); return head; } // Copy the string from the head pointer into the container void PrintList ( wordList_t *head ) { while ( head != NULL ) { printf ( "%s ", head->words ); head = head->next; } // Display held word, advance pointer to next node printf ( "\n" ); } // Move carriage to new line int main ( void ) { char c; int i, j = 0; char val3[1024]; filetext_t *list = NULL; // Create variables for reading from files and container for words FILE *fp = fopen ( "example.txt", "r" ); // Open example file doing away with user input for ( i = 0; ( c = fgetc ( fp ) ) != EOF; i++ ) { if ( isalpha ( c ) ) val3[j++] = tolower ( c ); // Copy alphabetic characters into the val3 container else { val3[j++] = '\0'; list = AddToList ( list, val2 ); j = 0; } // Otherwise insert blank space to seperate words } PrintList ( list ); fclose ( fp ); return 0; // Close open file, and print through list }

I try and run it and I get the error. Also, I strongly believe my malloc functions are corect, but the compiler things they're wrong. I looked in the Standord Linked List guide (which I found to be really useful and would strongly recommend to those like myself who are learning C) but it also shows similar syntax.

Any help with this would be much appreciated. I just can't wrk out what's wrong and why Windows keeps complaining. I can't even test for correct output as I can't run it in the first place!

Thanks.

Hussein.
11-12-2006
Richie T

If that code compiles, then you've got issues with your compiler, or you haven't supplied all the code. I direct your attention to the following:

Code:

typedef struct filelist { int val; char words[1024]; struct filetext *next; } filetext_t; // Create a structure to hold words and frequency, with sub-structure or next pointer . . . void PrintList ( wordList_t *head ) { while ( head != NULL ) { printf ( "%s ", head->words ); head = head->next; } // Display held word, advance pointer to next node printf ( "\n" ); } // Move carriage to new line int main ( void ) { . . . else { val3[j++] = '\0'; list = AddToList ( list, val2 ); j = 0; } . . . }

Figure out what's going on there, and I'll also be very nice and give you a couple of pointers:

1. fgetc returns int
2. you should always check to see if a file stream opened before using it - like checking the return value of fopen
3. If the compiler says that your calls to malloc are wrong, make sure you are compiling the code as C and not C++
11-12-2006
hpteenagewizkid

Oh my God!

sorry about that, but I never realised just changing the name of my typedef would have such an effect - how could that have been causing the malloc errors when the compiler didn't even mention anything about it? Actually, I only just found that when I was half way through writing my response here.

Done: Added a test for the file open command
Done: Added explicit definition for val2[]
Done: Changed random variable mismatch declaration

sorry, but I'm baffled on the fgetc issue. It's an int, and produces unsigned chars. therefore, would it not map those chars to the alpha characters referred to in the if statement, and then cross match them back to their numeric values for the tolower statement? I thought that was automatically handled by C?

Really baffled on why the incorrect name for the typedef would manifest itself with the malloc bit. As soon as I changed it to match the rest of the program, voila, no errors!

the problem I'm having now is, oh and by the way for some reason the file is now running without the Windows encountered a problem error, but it gets to the file open check and exits. I.e it doesn't print the list of words in the example file, which is basically This is an example file. So it should be outputting 1 1 1 1 1 but all on a new line.

Thanks, at least we're getting somewhere. Should give me some encouragement to work through the rest of the night.

If anyone can suggest an explanation for the relationship between typedef and malloc, and why the compiler kept shut about it, I'd be interested to learn.

Hussein.
11-13-2006
Richie T

Link on fgetc

It returns the ASCII value of the character being read - when you assign it to a char, it becomes the value you expect. If reading from the stream fails, it will return EOF, which the FAQ will tell you is an int, not a char - hence, fgetc returns int for that reason.

Code:

FILE *fp = fopen ( "example.txt", "r" );

for this line of code to work, the file must be in the current directory - what I normally do is compile my code, go to the directory where the executable is produced, and move my data file there (or vice versa), rather than allow the executable to be run from the IDE - long story short, make sure that the file is in the current directory.

I don't know what errors you got regarding malloc, that's why I suggested you make sure that you are compiling as C, not C++ - That's the most common problem with malloc in my experience. The problem in the struct that I was referring to was that filetext is not a valid type (caused by a typo probably, noting the lack of _t) - in fact, inside the struct, filetext_t is not even valid - this is because the typedef occurs after the struct is declared, and you would be trying to use filetext_t inside the struct, so it doesn't make sense. When I compiled your code, I changed the filetext (inside the struct) to filelist. Hopefully that clears things up, if only just a little.

In any case, I recommend posting your compiler/OS/original compiler error messages (so we can pinpoint what you are misunderstanding), and also perhaps updating your code in your first post (rather than reposting it again with small differences) so we can help fix the current problems.
11-13-2006
hpteenagewizkid

Ok. Thanks for your reply. I think I'm starting to understand C functions returning different data types than you are actually using them for (e.g using fgetc to get characters but the function returning ints).

I have no idea what I've done, but the problem is fixed. No errors with the compiler. However, the problem now is that the problem stops at "Test file opened successfully" and won't actually print the nodes, with their frequency (referred to with int val in the struct).

I'm even more baffled now, as I didn't actually do anything to the malloc part, and stupid me I don't have the original copy of the program to check comparisons - Bloodshed Dev C++ doesn't have a CVS or revision monitor facility.

Here's the code anyway:

Code:

/* References: C by Example C in a Nutshell C Primer 5th Edition Stanford CS Guide to Linked Lists C Reference Library (Functions) */ #include <stdio.h> #include <string.h> #include <stdlib.h> #include <ctype.h> typedef struct filetext { int val; char words[1024]; struct filetext *next; } filetext_t; // Create a structure to hold words and frequency, with sub-structure or next pointer char val2[1024]; filetext_t *AddToList ( filetext_t *head, char val2[] ) { // Function, create holder for current word filetext_t *current = NULL; // Set an initialising pointer set to NULL if ( head == NULL ) { head = malloc ( sizeof *head ); head->next = NULL; } // If head pointer is NULL, free memory and link to next pointer else { current = malloc ( sizeof *current->next ); current->next = head; head = current; } // Otherwise first node is created so create next node strcpy ( head->words, val2 ); return head; } // Copy the string from the head pointer into the container void PrintList ( filetext_t *head ) { while ( head != NULL ) { printf ( "%s", head->words ); head = head->next; } // Display held word, advance pointer to next node printf ( "\n" ); } // Move carriage to new line int main ( void ) { char c; int i, j = 0; char val3[1024]; filetext_t *list = NULL; // Create variables for reading from files and container for words FILE *fp = fopen ( "example.txt", "r" ); // Open example file doing away with user input if ( fp == NULL ) { printf("Open Failed!"); } else { printf("Test file opened successfully"); } for ( i = 0; ( c = fgetc ( fp ) ) != EOF; i++ ) { if ( isalpha ( c ) ) val3[j++] = tolower ( c ); // Copy alphabetic characters into the val3 container else { val3[j++] = '\0'; list = AddToList ( list, val2 ); j = 0; } // Otherwise insert blank space to separate words } PrintList ( list ); fclose ( fp ); return 0; // Close open file, and print through list }

Thanks again for the link - another useful reference to have. Also, could I just say the links in your signature were also useful.

Hussein.
11-13-2006
thoseion

Quote:

Originally Posted by hpteenagewizkid

Code:

// Copy alphabetic characters into the val3 container else { val3[j++] = '\0'; list = AddToList ( list, val2 ); <- This should be val3, not val2 j = 0; } // Otherwise insert blank space to separate words } PrintList ( list ); fclose ( fp );

Hussein.

I believe the problem is due to a simple variable naming error - you've named your character array val3 but when you send it to AddToList, your actually sending val2.
11-14-2006
dwks

Quote:

I think I'm starting to understand C functions returning different data types than you are actually using them for (e.g using fgetc to get characters but the function returning ints).

Usually C functions return something reasonable. fgetc() returns an int so that it can return EOF to indicate an error or end of file. EOF isn't a character; if it was, then fgetc() could conceivably return it. :) EOF can only be stored in an int, not a char, so that's what fgetc() returns.

BTW, getc() is usually a macro implementation of fgetc() -- so it might be faster to use it instead. Otherwise they're identical.