Storing details into C Structure - c

Question

I'm writing the C program to find the function and calculate the number of lines of a function in C file and I am storing it into a structure. I've given my codes below.
#include <stdio.h>
#include <string.h>
#define SIZE 1024
struct fundetails
{
int nooflines;
char *funcname;
}s[20];
char *ffname(char *line)
{
int i=1,j=0;
char *dt;
char name[SIZE];
strtok(line,"(");
dt = strchr(line,' ');
if(dt[i] == '*')
i++;
while(dt[i] != '\0')
{
name[j]=dt[i];
i++;
j++;
}
name[j] ='\0';
return name;
}
int main(int argc, char **argv)
{
if(argc < 2)
{
printf("Give the filename \n");
printf("Usage: %s filename\n", argv[0]);
return -1;
}
int i, lines =0, funlines =0,count =0, fn =0, flag =0, size=0,emptyflag=0;
char c[SIZE],b[SIZE];
char *fname;
FILE *fd;
fd = fopen(argv[1],"r");
while(fgets(c,SIZE,fd))
{
emptyflag=0;
lines++;
size = strlen(c);
if(size == 1 && (strcmp(c,"\n"))== 0)
emptyflag=1;
for(i=0;i<size;i++)
{
while( c[i] =='\t' || c[i] == ' ')
{
i++;
}
if( c[i] == '{')
{
count++;
if(flag)
{
if(!emptyflag)
funlines++;
else
emptyflag=0;
}
if(count == 1)
{
fn++;
printf("Function %d is Started..............\n", fn);
flag = 1;
fname=ffname(b);
printf("Function name is:%s\n",fname);
}
break;
}
else if( c[i] == '}')
{
count--;
if(!count)
{
flag = 0;
printf("No of lines in the function %d is: %d\n", fn, funlines);
printf("Function %d is finished..........\n", fn);
s[fn-1].nooflines=funlines;
s[fn-1].funcname=fname;
funlines = 0;
}
else
{
if(!emptyflag)
funlines++;
else
emptyflag=0;
}
break;
}
else if(flag)
{
if(!emptyflag)
funlines++;
else
emptyflag=0;
break;
}
}
strcpy(b,c);
}
printf("FUN_NAME\tNO_OF_LINES\n");
for(i=0;i<fn;i++)
{
printf("%s\t\t%d\n",s[i].funcname,s[i].nooflines);
}
return 0;
}
It produces warning as try.c:26:2: warning: function returns address of local variable [enabled by default]. And It produces output as given below.
Function 1 is Started..............
Function name is:fundetails
No of lines in the function 1 is: 2
Function 1 is finished..........
Function 2 is Started..............
Function name is:dhahira
No of lines in the function 2 is: 1
Function 2 is finished..........
Function 3 is Started..............
Function name is:add
No of lines in the function 3 is: 3
Function 3 is finished..........
Function 4 is Started..............
Function name is:sub
No of lines in the function 4 is: 9
Function 4 is finished..........
Function 5 is Started..............
Function name is:main
No of lines in the function 5 is: 13
Function 5 is finished..........
FUN_NAME NO_OF_LINES
main 2
main 1
main 3
main 9
main 13
I'm storing function name and no of lines in same loop.WQhile i1m running it in GDB,for each time of
s[fn-1].nooflines=funlines;
s[fn-1].funcname=fname;
above line,the number of line is storing in a structure correctly.But not in the case of
function name.
Problem:I don't understand that why is it working properly for line and not working for function name? is it because of that warning? Please guide me, Thanks.

Answer 1

In ffname(), name[] is local, it's pushed to stack when execute the function. After ffname() return, the stack is popped, that means the memory seized by name[] got released, system could reuse the memory, but before the memory is reused, data is still there. That's why sometime it works and sometime not. Also, that's why you get warning.
You should define funcname in the struct as array rather than pointer. Because when funcname, you always point funcname to same name[], while name[] is written in each loop, so that at last you print same name 5 times.
After you change funcname to array, you should use strcpy to copy name:
strcpy(funcname, name); // this is right way when funcname is array
Rather than:
funcname = name;

Answer 2

First make the struct
struct fundetails
{
int nooflines;
char funcname[128];
}s[20];
then fix the returning value of the func ffname: you can't return a pointer to data that will disappear going out of scope (in this case, the function's end). As cheap quick modification, just turn your
char name[SIZE];
into
static char name[SIZE];
Then
strcpy(s[fn-1].funcname, fname);
instead of your
s[fn-1].funcname=fname;
The output would be like
FUN_NAME NO_OF_LINES
fundetails
2
ffname 15
main 82
I haven't checked how you identify functions but it seems too much naive. (The answer may not fix all the problem of your code; e.g. there could be path in your code that brings to the use of fname before it being assigned?...)