Hmm... Anything wrong with this?

This is a discussion on Hmm... Anything wrong with this? within the C++ Programming forums, part of the General Programming Boards category; I use the function below for logging in my program. All it does is write the line I input into ...

  1. #1
    Registered User jon_nc17's Avatar
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    Question Hmm... Anything wrong with this?

    I use the function below for logging in my program. All it does is write the line I input into an array, and shift the oldest line out. I thought it was working fine, but this morning I wrote some code to handle serial input and things went haywire. What I was doing was just calling the logit function every time I received a complete packet like this LogIt("Packet Received [%s], packet_data"); Every time I ran the program, the program would randomly freeze-up after a random amount of packets... I checked, and double checked the code, and then went as far as taking out the LogIt function... and then it worked.

    I've gone back and looked at the code, but I can't find anything wrong with it -- except that it is messy =) All the '\0' positions & lengths seem to be ok, but am I over looking something?

    Code:
    // --------------
    // LOG FUNCTION
    // --------------
    LogIt( char *newline, ... ) {
    	va_list arg_ptr;
    	va_start(arg_ptr, newline);
    	char newlinef[88]; // 88 because on the log line there 
    // will be a 12 character time string added on (see below) for a 
    // total of 100
    
    	vsprintf(newlinef, newline, arg_ptr);
    	va_end(arg_ptr);
    
    	time_t t = time(0);
    	char *date = ctime(&t);
    	date[19] = '\0';
    	char *ampm = "AM";
    	char hour[3] = "";
    	int inthr;
    	hour[0] = date[11];
    	hour[1] = date[12];
    	inthr = atoi( hour );
    	if( inthr == 12 ) {
    		strcpy( ampm, "PM" );
    	} else if( inthr > 12 ) {
    		inthr -= 12;
    		strcpy( ampm, "PM" );
    	} else if( inthr == 0 ) {
    		inthr += 12;
    	}
    
    	itoa( inthr, hour, 10 );
    	if( inthr > 9 ) {
    		date[11] = hour[0];
    		date[12] = hour[1];
    	} else {
    		date[11] = ' ';
    		date[12] = hour[0];
    	}
    	char msg[13]; // Time should come out to be in this 
    // format "00:00:00AM: " -- 12 characters
    	strcpy( msg, &date[11] );
    	strcat( msg, ampm );
    	strcat( msg, ": " );
    	char sepnewline[100];
    	strcpy(sepnewline, msg);
    	strcat( sepnewline, newlinef );
    	char templine[100];
    	int i;
    	for(i=0;i<50;i++)	{
    //save current string
    		strcpy(templine,LogLines[i].Line); 
    //replace with new one
    		strcpy(LogLines[i].Line,sepnewline);  
    //reset new one to former one
    		strcpy(sepnewline,templine);       
    	}
    	return 1;
    }
    Thanks,

    Jon Scott
    Last edited by jon_nc17; 12-01-2002 at 06:47 PM.

  2. #2
    End Of Line Hammer's Avatar
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    >>char *ampm = "AM";
    >>strcpy( ampm, "PM" );
    This is not legal practice. You are trying to overwrite a string literal.
    Code:
    char *ampm;
    
    if (hour < 12)
        ampm = "AM";
    else
        ampm = "PM";
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  3. #3
    Registered User jon_nc17's Avatar
    Join Date
    May 2002
    Posts
    15

    Thumbs up

    It works, thank you! Geeze, I would have never guessed that was not allowed... Anyway, thank you -- good learning experience for me!

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