sizeof question

I was noticing that if you use sizeof to get the size of a char array that is not from to the function you are calling it from, it doesn't work. Even if you have a function that takes in a string, like function(char *string); and you refer to it as "string" instead of it's actual declaration name it still doesn't. Am I doing something wrong, and if not, anyone know why this is so?

Code:

---


void ash(char *string);

main() {

char str[50];

//sizeof would work fine here

return 0;
}

void ash(char *string) {

printf("%d", sizeof(string)); <--why doesn't this work?

printf("%d", sizeof(str)); // <--I understand why this doesn't  work, can't access a local var outside it's function

} //

---

btw, the freeware version of my program is done! as soon as i get a webpage to store it on, i'll post it here for all to d/l, cause i certainly couldn't have done it w/o everyone's help :)

You're getting the size of the pointer, not the size of the array.

The size of a pointer is 32 bits on a 32 bit OS which translates to 4 bytes.

The function is working perfectly, it's just doing something you didn't expect it to do :)

In this situation you should create your function so that the size of the array is specified.

eg.

Code:

---

char str[10];
fgets(str,sizeof(str),stdin);

---

Other functions are fread, fwrite and lots of others that do this.

Quote:

---

Originally Posted by Ash1981

btw, the freeware version of my program is done! as soon as i get a webpage to store it on, i'll post it here for all to d/l, cause i certainly couldn't have done it w/o everyone's help :)

---

You can attach source code files to posts :)

Read this -> http://c-faq.com/aryptr/index.html
Focus on the parts which tell you about how arrays decay to pointers when you pass an array to a function (for example).

sizeof(array) is one of the exceptional cases in which an array does not decay to a pointer, but since there is a function call in the way in your example, then it's already too late.

thanks for the replies, i'm still modifying the source code a bit, then i'll post it :)

btw, I had a couple of other small questions that have been bugging me:

Is there a way to convert a string into an integer or vice versa? I googled this, but I kept getting visual basic hits, lol.

I know in the main function I always use exit(0) so the OS knows all went well, but if there is an error, do you use exit(1) or exit(-1), or if not those, what do you use, and what does this actually do?

I know how to stop Ctrl-C from stopping my program, but how about ctrl-break?

Thanks again :)

Oh one more thing, if anybody happens to read this, you know how you can usually right click on a program and select properties under winx, and it will allow you to change the icon of the program, and offer you a list of icons to choose from? well get this, that's not an option on mine, so I have to stick with the regular windows console icon...

Quote:

---

Originally Posted by Ash1981

thanks for the replies, i'm still modifying the source code a bit, then i'll post it :)

btw, I had a couple of other small questions that have been bugging me:

Is there a way to convert a string into an integer or vice versa? I googled this, but I kept getting visual basic hits, lol.

I know in the main function I always use exit(0) so the OS knows all went well, but if there is an error, do you use exit(1) or exit(-1), or if not those, what do you use, and what does this actually do?

I know how to stop Ctrl-C from stopping my program, but how about ctrl-break?

Thanks again :)

---

1. well, there are few lib fucntion to do that job that is to convert from string to int and visa versa. u can always look through atoi fucntion to get string to integer and itoa from int to string. as itoa fucntion is not a stand fucntion its better to use sprintf to covert from string to int

2. its better to say return 0 or return 1 rather than exit(0) or exit(1). its just record for the OS. like for example if some file is not opened properly we normally say return 1 if you are in the main. returns are used only in the main

3. clt-C is commanly used in the linux platforms and clt-break on wndows plat still clt-c works fine. i dont think there is any diff in clt-break and clt-C

ssharish2005

Quote:

---

Originally Posted by Ash1981

I know in the main function I always use exit(0) so the OS knows all went well, but if there is an error, do you use exit(1) or exit(-1), or if not those, what do you use, and what does this actually do?

---

If you include stdlib.h you can use "exit (EXIT_SUCCESS)" and "exit (EXIT_FAILURE)" ... (on my system these are defined as 0 and 1 respectively).