pointer assignment

Andrea G.

Hello,

I'm trying to use this assignment:

if (ptrHalltoDCPhase120_CMP[ulHall]!=NULL) { ptrDC_Phase_CMP = ptrHalltoDCPhase120_CMP[ulHall] ; }

but I get this error:

error: a value of type "const volatile unsigned long *" cannot be assigned to an entity of type "volatile unsigned long *"

any ideas why this does not work? I'm taking a constant and putting it in a variable...

Thanks,

Andrea

over 13 years ago

0 Archaeologist over 13 years ago

TI__Guru* 84285 points

The error message says you are copying a pointer to a pointer, and the types of these pointers do not match. The type "const X *" is a different type than "X *".

Clearly ptrHalltoDCPhase120_CMP is an array of pointers. I'm guessing ptrDC_Phase_CMP is a pointer, as well.

It may be that what you want here is a cast, but I'd need to see more of the test case before I make a recommendation. It may instead be the case that you should change the declaration of one of these two variables.

0 Andrea G. over 13 years ago in reply to Archaeologist

Intellectual 370 points

Hi,

thanks for the quick asnwer.

the declarations are:

static const volatile unsigned long * ptrHalltoDCPhase120_CMP[8] = {
NULL,
&PWM_2_CMPA_R,
&PWM_1_CMPA_R,
&PWM_2_CMPA_R,
&PWM_0_CMPA_R,
&PWM_0_CMPA_R,
&PWM_1_CMPA_R,
NULL
};

and

volatile unsigned long * ptrDC_Phase_CMP ;

where

#define PWM_1_CMPA_R (*((volatile unsigned long *)0x40028098))

Does this help?

Thanks,

Andrea

0 Archaeologist over 13 years ago in reply to Andrea G.

TI__Guru* 84285 points

I'm pretty sure you want:

static volatile unsigned long * const ptrHalltoDCPhase120_CMP[8]

This declares the array as an array of constant pointers; the way you have it, it is an array of pointers to constant. Please see http://c-faq.com/ansi/constptrconst.html

0 Andrea G. over 13 years ago in reply to Archaeologist

Intellectual 370 points

I am sooooo impressed! (and a little ashamed)

Thanks,

Andrea

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pointer assignment