Can't assign value to a variable inside a for loop - c

Question

Here is what I want to do:
Read all characters from a '.c' file and store that into an array.
When a character from that array is '{', it will be pushed into a stack. And count of pushed characters will be increased by 1.
When a character from that array is '}', stack will pop and the count of popped characters will be increased by 1.
Compare those two counts to check whether there is a missing '{' or '}'
Here is my code:
int getLinesSyntax(char s[], int limit, FILE *cfile)
{
int i, c, push_count = 0, pop_count = 0;
int state = CODE;
int brackets[limit];
char braces[limit];
for(i = 0; i < 100; i++)
{
braces[i] = 0;
}
for(i = 0; i < limit - 1 && (c = getc(cfile)) != EOF && c != '\n'; i++)
{
s[i] = c;
if(s[i] == '{')
{
braces[0] = s[i];
//push(s[i], braces);
++push_count;
}
else if(s[i] == '}')
{
pop(braces);
++pop_count;
}
}
//Mor shiljih uyed array -n togsgold 0-g zalgana
if(c == '\n')
{
s[i] = c;
i++;
}
s[i] = '\0';
i = i -1; //Suuld zalgasan 0 -g toonoos hasna
if(c == EOF)
{
//just checking
for(i = 0; i < 100; i++)
{
printf("%d", braces[i]);
}
if(push_count != pop_count)
{
printf("%d and %d syntax error: braces", push_count, pop_count);
}
return -1;
}
else
{
return i;
}
}
Here is the output
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
The problems is:
Assignments inside the for loop is not working. (It's working when I put that outside of the loop)
I would like to know if there's something wrong with my code :).

Answer 1

There are several problems.
Lets go through it step by step
1) Your array initialization loop:
int brackets[limit];
char braces[limit];
for(i = 0; i < 100; i++)
{
braces[i] = 0;
}
You declare the array having size of limit but only initialize 100 items. Change 100 to limit to fully initialize it depending on the parameter of the function.
2) The conditional statement of the main for loop:
i < limit - 1 && (c = getc(cfile)) != EOF && c != '\n'
Although the first substatement is correct I have two remarks:
Firstly (c = getc(cfile)) != EOF might be one reason why the loop is never accessed and still everything is 000000.... Check if the file exists, the pointer is not NULL or other silent errors occured.
Secondly the c != '\n'. What if one of these characters occurs? In this case you won't continue with the next iteration but break out of the entire forloop. Remove it there and put it in the first line of the body like this:
if(c == '\n')
{
i -= 1; // to really skip the character and maintain the index.
continue;
}
3) s[i] = c;
Can you be certain, that the array is indeed sizeof limit?
4) Checking for curly braces
if(s[i] == '{')
{
braces[0] = s[i];
//push(s[i], braces);
++push_count;
}
else if(s[i] == '}')
{
pop(braces);
++pop_count;
}
You assign to braces[0] always, why?
5) Uninitialized access
if(c == '\n')
{
s[i] = c;
i++;
}
s[i] = '\0';
i = i -1; //Suuld zalgasan 0 -g toonoos hasna
You're now using the function-global variable i, which is never initialized properly for this block. What you do is to use a variable that is used basically everywhere ( which is basically also no problem from the memory point of view. ), but you rely on legacy values. Is this done by purpose? If no, reinitialize i properly. I have to ask this since i can't read your comments in code.
What I'm quite unhappy about is that you entirely rely on one variable in all the loops and statements. Usually a loop-index should never be altered from inside. Maybe you can come up with a cleaner design of the function like an additional index variable you parallelly increase without altering i. The additional index will be used for array access where appropriate whereas i really remains just a counter.

Answer 2

I think the problem is in this condition "c != '\n'" which is breaking the for loop right after the first line, before it reaches any brackets. And hence the output.

Answer 3

For the task of counting whether there are balanced braces in the data, the code is excessively complex. You could simply use:
int l_brace = 0;
int r_brace = 0;
int c;
while ((c = getchar()) != EOF)
{
if (c == '{')
l_brace++;
else if (c == '}')
r_brace++;
}
if (l_brace != r_brace)
printf("Number of { = %d; number of } = %d\n", l_brace, r_brace);
Of course, this can be confused by code such as:
/* This is a comment with an { in it */
char string[] = "{{{";
char c = '{';
There are no braces that mark control-of-flow statement grouping in that fragment, for all there are 5 left braces ({) in the source code. Parsing C properly is hard work.