C : Debugging & Run - Different Output

Question

i'm using code-blocks 16.01 when i debug this code it show me a correct output but when i run it it show incorrect output! how to solve this?

int main()
{
    char ch[100],var[100],val[100],tempVa[100];
    int i = 0,j=0,count=0;
    while (1)
    {
        puts("Enter the expression (or (end) to exit):");
        gets(ch);
        if (strcmp(ch, "end") == 0 || strcmp(ch, "END") == 0)
            exit(-1);
        else if(2 == sscanf(ch,"%s = %s", var, val))
        {   i = 0;
            printf("Variable is : %s\t Value Before evaluating : %s\n",var, val);
            while (i<=strlen(val))
            {
                while (val[i]!='-'&&val[i]!='%'&&val[i]!='/'&&val[i]!='*'&&val[i]!='+'&&i<strlen(val))
                    tempVa[j++]=val[i++];

                i++;
                for (count=0; count<strlen(tempVa); count++)
                    printf("%c", tempVa[count]);
                for (count=strlen(tempVa); count>=0; count--)
                    tempVa[count]='\0';
                j=0;
            }
        }
        else
            printf("Invalid!");
    }
    return 0;
}

Smaple Input : Hassan = Merna+Mohamed+Ahmed

Debugging Output

Run Output

From where does those garbage come?!

Your images are not working. Could you write the output in text format? — Erik W
– Erik W, Commented May 15, 2017 at 21:04
hint: you need to null-terminate tempVa after you copy contents into it. In debug, it is likely zeroed out at start, but in release, it's just whatever's in the memory at the time. — Joe
– Joe, Commented May 15, 2017 at 21:04
@ErikW Run : i.sstatic.net/mmR5e.png Debug : MernaMohamedAhmed — Hassan A. El-Seoudy
– Hassan A. El-Seoudy, Commented May 15, 2017 at 21:07
@Joe` for (count=strlen(tempVa); count>=0; count--) tempVa[count]='\0';` i already Nulled it here i think. — Hassan A. El-Seoudy
– Hassan A. El-Seoudy, Commented May 15, 2017 at 21:09
Another pic of Run, sometimes it works, some times it doesn't work .. i don't know what is the reason :( link — Hassan A. El-Seoudy
– Hassan A. El-Seoudy, Commented May 15, 2017 at 21:11

Ahmed Hamdy · Accepted Answer · 2017-05-15 22:38:50Z

I tested your code and it works Edits:

You should import the string.h library (anyways, you should always resolve any warning you have).
Use return -1, that is why main is an int function.
Like @joe said in the comments, you should always terminate your string with '\0'.

Code:

#include <stdio.h>
#include <string.h> // edit

int main()
{
    char ch[100], var[100], val[100], tempVa[100];
    int i = 0, j = 0, count = 0;
    while (1)
    {
        puts("\nEnter the expression (or (end) to exit):");
        gets(ch);
        if (strcmp(ch, "end") == 0 || strcmp(ch, "END") == 0)
            return -1; // edit
        else if(2 == sscanf(ch, "%s = %s", var, val))
        {
            i = 0;
            printf("Variable is : %s\t Value Before evaluating : %s\n", var, val);
            while (i <= strlen(val))
            {
                while (val[i] != '-' && val[i] != '%' && val[i] != '/' && val[i] != '*' && val[i] != '+' && i < strlen(val))
                    tempVa[j++] = val[i++];

                i++;
                for (count = 0; count < strlen(tempVa); count++)
                    printf("%c", tempVa[count]);
                for (count = strlen(tempVa); count >= 0; count--)
                    tempVa[count] = '\0';
                j = 0;
            }
        }
        else
            printf("Invalid!");
    }
    return 0;
}

Sample run:

Enter the expression (or (end) to exit): Hassan = Merna+Mohamed+Ahmed
Variable is : Hassan Value Before evaluating : Merna+Mohamed+Ahmed MernaMohamedAhmed
Enter the expression (or (end) to exit):

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