struct problem.

Guest · Posted: Wed Mar 04, 2009 3:57 pm

Hi

CCS: 4.083 / PIC:18xx2455

There are some problem in the asm, of this simple struct.
But the code compile and run, but the asm look real funny.

Can anybody explain what going on here?

(not production code just for testing!)

andrewg · Posted: Wed Mar 04, 2009 10:15 pm

The 'c' in x1[c] is a variable, and the compiler needs to generate code to calculate the address of x1[c].

Then the compiler needs to add to that address the offset of the struct items. For v1, it's at the start of the struct and presumably has a zero offset. That can be optimised away. v2 is not at the start of the struct, so extra code to add its offset is required.

When working with x1[2], the addresses can be calculated at compile time, and used directly in the code.
_________________
Andrew

Guest · Posted: Thu Mar 05, 2009 1:37 am

Hi

If changing to another chip 16xx the code is real clean. I dont have the 4.084 but in the release list I can see that some 18xx problem is solved.

Seoman · Guest

I change some code, i would like to use a string inside the structure

Guest · Posted: Thu Mar 05, 2009 10:59 am

My Compiler is 4.065

sorry

Ttelmah · Guest

Nothing to do with the structure. You need to use strcpy, to copy strings. C can automatically move 'simple' types (numbers etc.), but strings are more complex, and can't be copied with a simple '='.

Best Wishes

Wayne_ · Joined: 10 Oct 2007 Posts: 681

Try
sprintf(x1[2].v3, "Hello"); or
strcpy(x1[2].v3, "Hello");

You can only do a char array assignment at declaration of the var
char mystr[10] = "hello";