CodeWarrior for MCUのトピックRe: Why const is not const?

Why const is not const?

Teckna — Wed, 28 Nov 2012 16:19:52 GMT

Hi everyone,

I'm working with CW 10.2 and Kinetis MK60DN512.

I created a bareboard project with a single test file:

#include <stdio.h>

#include "derivative.h" /* include peripheral declarations */

typedef struct
{
const char *str;
} TEST;

const TEST Test0 =
{
"STRING0"
};
const TEST Test1 =
{
"STRING1"
};

const TEST *Test[ 2 ] =
{
&Test0,
&Test1
};

int main( void )
{
int i;

for( i = 0; i < 2; i++ )
printf( Test[ i ]->str );

     while( 1 )
     {
          i++;

}

return( 0 );
}

In the map file the two const structs Test0 and Test1 are located in .rodata section (flash), but the const struct Test is located in the .app_data section (ram) even if it's declared as const.

Why is there such difference? I expected all the structs to be located in the .rodata section.

Many thanks

Teckna

Re: Why const is not const?

BlackNight — Wed, 28 Nov 2012 18:36:16 GMT

Hello,

because Test[] is not const. Test is a non-const array of two pointers to const structs.

To make it const, you have to define it as

const TEST *const Test[] =

Erich

Re: Why const is not const?

mjbcswitzerland — Wed, 28 Nov 2012 22:03:27 GMT

See the following for some ideas about forcing more things to Flash - it is for CW7 but may be the same for CW10

reducing ram footprint

Regards

Mark

Re: Why const is not const?

Teckna — Thu, 29 Nov 2012 15:17:58 GMT

Many thanks, Erich,

Teckna