Thread: ! C question: simple integer function passing

Could someone clarify this for me?

I dont understand why case 1 works and why case 2 doesn't.
the compiler gives a warning, complaining about code has no effect for case 2

case1:

------------------------------------
void func1( void )
{

int s_count;

func2( &s_count );

}

void func2( int *count )
{
count++;
}
------------------------------------

case 2:
------------------------------------
void func1( void )
{

int s_count;

func2( &s_count );

}

void func2( int *count )
{
*count++;
}
------------------------------------

thank you for your reply

i ran and output the integer data on the lcd

it was still zero
even though i incremented it in func2

HOWEVER i think i may have found something,

the compiler complains when i use

count++;

but it is happy when i use

count += 1;

BAH! STUPID COMPILER :P

give me a few seconds i think it may be solved, just a fussy compiler.

yes it works now, weird.

it is happy with += but not with the ++ when i call in a int pointer.

damn compiler

instead of doing *count++;

i had to do *count += 1;

for it to work.

i'm working on an embedded env.

case 2 works, this is what i have:
------------------------------------------------------------------------------------
void func1( void )
{
int s_count;

func2( &s_count );

puts_lcd( s_count ); // <-- puts_lcd() does the output to lcd
}

void func2( int *count )
{
*count += 1;
}
------------------------------------------------------------------------------------

Originally Posted by aaronc

yes it works now, weird.

No it's not. Reread all of your posts. Some times you put:

Code:

count++;

Then you put:

Code:

*count++;

As stated by Codeplug, they are definately not the same thing. In your first code example, you don't dereference. Thus, you don't change the value of what's being pointed at, you change what you're pointing at. (Which has no effect, because that goes out of scope at the end of the function call.)

Quzah.

sorry my wording was incorrect in the first post.

what i meant was "works" as in "compiles with no warnings".

not "works" as in "compiles with warnings".

my apologies,

this particular compiler complains about using post increment (*count++) when passing an int as a pointer. So i had to use *count += 1; instead

thanks dante

now why didn't i think of that earlier... the dreaded brackets

is there any advantage to using

Code:

(*count)++;

in comparison to

Code:

*count += 1;

, or vice versa?

None that I imagine.
*count += 1;
has the desired effect.