Page Fault in Visual C++

This is a discussion on Page Fault in Visual C++ within the C Programming forums, part of the General Programming Boards category; Good evening all. I have a problem with the code I am trying to write that separates an expression into ...

  1. #1
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    Page Fault in Visual C++

    Good evening all. I have a problem with the code I am trying to write that separates an expression into an array. I continually get a invalid page fault in Visual C++ (6). Although I didn't try it on the UNIX server, this usually indicates a segmentation fault on UNIX.

    Would someone mind looking at the code below and see why I might be getting a segmentation fault?? T-I-A


    Code:
    #include<stdio.h>
    #include<string.h>
    #include<ctype.h>
    
    main()
    
    	{
    
    	char array[100], exp[100], id[10], num[10], digit[10], letter[10];
    	int i=0, j=0;
    
    	printf("Please enter an expression: ");
    	scanf("%s", exp);
    
    	printf("%s\n", exp);
    
    	if (exp[i] == '(')
    		array[i] = 20;
    		else if(exp[i] == ')')
    			array[i] = 21;
    		else if(exp[i] == '+')
    			array[i] = 16;
    		else if(exp[i] == '-')
    			array[i] = 17;
    		else if(exp[i] == '*')
    			array[i] = 18;
    		else if(exp[i] == '/')
    			array[i] = 19;
    
    		else if(isdigit(exp[i]))
    			while(isdigit(exp[i])){
    				*digit = exp[i];
    				*num = strcat(num, digit);
    				++i;}
    		else if(isalpha(exp[i]))
    			while(isalpha(exp[i])){
    				*letter = exp[i];
    				*id = strcat(id, letter);
    				++i;}
    	else
    		printf("%c is invalid\n", exp[i]);
    
    for(j=1; j<100; j++)
    	{
    	printf("%c\n",array[j]);
    }
    
    
    }

  2. #2
    Comment your source code! Lynux-Penguin's Avatar
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    GOT IT!
    try this
    note: scanf you forgot the & (address of)
    Code:
    #include <stdio.h>
    #include <string.h>
    #include <ctype.h>
    
    int main()
    
    	{
    
    	char array[100], exp[100], id[10], num[10], digit[10], letter[10];
    	int i=0, j=0;
    
    	printf("Please enter an expression: ");
    	scanf("%s", exp);
    
    	printf("%s\n", exp);
    
    	if (exp[i] == '(')
    		array[i] = 20;
    	else if(exp[i] == ')')
    		array[i] = 21;
    	else if(exp[i] == '+')
    		array[i] = 16;
    	else if(exp[i] == '-')
    		array[i] = 17;
    	else if(exp[i] == '*')
    		array[i] = 18;
    	else if(exp[i] == '/')
    		array[i] = 19;
    
    	else if(isdigit(exp[i]))
    		while(isdigit(exp[i])){
    			*digit = exp[i];
    			*num = strcat(num, digit);
    				++i;}
    		else if(isalpha(exp[i]))
    			while(isalpha(exp[i])){
    				*letter = exp[i];
    				*id = strcat(id, letter);
    				++i;}
    	else
    		printf("%c is invalid\n", exp[i]);
    
    for(j=1; j<100; j++)
    	{
    	printf("%c\n",array[j]);
    }
    
    
    }
    note: ' ' is for character comparison
    " " is for string comparison...

    -Luke
    Asking the right question is sometimes more important than knowing the answer.
    Please read the FAQ
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  3. #3
    Im a Capricorn vsriharsha's Avatar
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    Thumbs up

    try this
    note: scanf you forgot the & (address of)
    Well, U need not specify the & (address of) operator for arrays and pointers (because, when u specify the variable name of an array, its base address is automatically referenced.

    code:--------------------------------------------------------------------------------
    #include <stdio.h>
    #include <string.h>
    #include <ctype.h>

    int main()

    {

    char array[100], exp[100], id[10], num[10], digit[10], letter[10];
    int i=0, j=0;

    printf("Please enter an expression: ");
    scanf("%s", exp);

    printf("%s\n", exp);

    if (exp[i] == '(')
    array[i] = 20;
    else if(exp[i] == ')')
    array[i] = 21;
    else if(exp[i] == '+')
    array[i] = 16;
    else if(exp[i] == '-')
    array[i] = 17;
    else if(exp[i] == '*')
    array[i] = 18;
    else if(exp[i] == '/')
    array[i] = 19;

    else if(isdigit(exp[i]))
    while(isdigit(exp[i])){
    *digit = exp[i];
    *num = strcat(num, digit);
    ++i;}
    else if(isalpha(exp[i]))
    while(isalpha(exp[i])){
    *letter = exp[i];
    *id = strcat(id, letter);
    ++i;}
    else
    printf("%c is invalid\n", exp[i]);

    for(j=1; j<100; j++)
    {
    printf("%c\n",array[j]);
    }


    }
    *letter=exp[i] etc.... Do they really work. U declared them as arrays not pointers.

    Then...

    note: ' ' is for character comparison
    " " is for string comparison...
    I've not seen direct string comparision in C. Use strcmp instead (defined in string.h)


    -Harsha.
    Help everyone you can

  4. #4
    Registered User
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    Originally posted by vsriharsha

    *letter=exp[i] etc.... Do they really work. U declared them as arrays not pointers.
    I'd expect so. Array identifies when used in an expression (except of course as the destination of an assignment) evaluate to a pointer to the first element of the array.

    Ian Woods

  5. #5
    Im a Capricorn vsriharsha's Avatar
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    Smile

    Yes it works....I myself said that when ever an array is referred, its base address is passed...

    Did the page fault problem come to an end now, reader?? Can
    char array[100], exp[100], id[10], num[10], digit[10], letter[10];
    int i=0, j=0;

    printf("Please enter an expression: ");
    scanf("%s", exp);
    be a problem...I mean, what if the entered expression is more than 100 chars. So, scanf can be re-written as...

    scanf("%100s",exp);

    Check it out.

    -harsha.
    Help everyone you can

  6. #6
    and the hat of wrongness Salem's Avatar
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    Those strcat functions leave a lot to be desired - your'e not copying chars, but the whole of the remaining string.

    The assignment
    *id = strcat(id, letter);
    is also wrong.


    If you do this often enough, you're going to fill up the buffer space pretty quick

    And how did vsriharsha manage to mangle the nicely formatted code?

  7. #7
    Im a Capricorn vsriharsha's Avatar
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    Cool

    originally posted by salem
    And how did vsriharsha manage to mangle the nicely formatted code?
    Its the grace of one of the best features of WINDOWS... COPY-PASTE.

    -Harsha.

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