"Expected a statement" error in embedded C

Question

I'm getting error like "expected an statement"

my code is as follows

#define IN_Tamper    0X00001000     /*P2.12 = EINT2*/
#define DIR_IN_Tamper    { FIO2DIR &= ~0X00001000 ; } 

/* main */
DIR_IN_Tamper(); 
if(((IN_Tamper >> 12) & 0x01) == 1)
            BUZZER_ON();
         else
            BUZZER_OFF();   

I'm getting error saying

1. Expected an statement for DIR_IN_Tamper();

2. expected a statement for the else part.....

Cutpurse

or defined like: #define DIR_IN_Tamper(FIO2DIR) { FIO2DIR &= ~0X00001000 ; }; and call like DIR_IN_Tamper(FIO2DIR); what is FIO2DIR ? – Tarragona

#define DIR_IN_Tamper { FIO2DIR &= ~0X00001000 ; } like this...... – Cutpurse

No I mean what is FIO2DIR ? if its macro then consider @phihag's answer. If its variable you wants to pass then defined like macro function as I suggested. – Tarragona

FIO2DIR is ARM7's key word... – Cutpurse

then Consider @phihag's answer, One think he didn't explain is that in macro definitional {} is used because programmer wants to give complete statement (including ;). If at the time of macro calling, suppose use forgets ; then it will not cause any error. – Tarragona

lastly I have removed () from every where n its working fine.. thank you all.. – Cutpurse

Answer 1

The C preprocessor is (at least in the way you use it) just a simple search-and-replace, so you're effectively running

/* main */
{ FIO2DIR &= ~0X00001000 ; } (); 

This doesn't make any sense. Remove the parentheses in the line

DIR_IN_Tamper(); 

For BUZZER_ON and BUZZER_OFF, you want to remove the parentheses as well. If the macro isn't enclosed in curly braces, you also want to add those, like

if(((IN_Tamper >> 12) & 0x01) == 1) {
    BUZZER_ON
} else {
    BUZZER_OFF
}

Olcott

for BUZZER_ON/OFF I have used macro – Cutpurse

like #define DIR_BUZ() FIO0DIR |= 0x10000000 ; //DIRECTION FOR BUZ PIn P0.28 #define B_BUZ_E(X) {(X==SET)? (FIO0SET |= PINO_BUZ) : (FIO0CLR |= PINO_BUZ) ;} #define BUZZER_ON() { DIR_BUZ(); B_BUZ_E(1); } #define BUZZER_OFF() { DIR_BUZ(); B_BUZ_E(0); } – Cutpurse

Answer 2

DIR_IN_Tamper is defined as { FIO2DIR &= ~0X00001000 ; }, therefore when the preprocessor parses your code, this line

DIR_IN_Tamper(); 

is converted into

{ FIO2DIR &= ~0X00001000 ; }()

Which is clearly not correct. Not sure what exactly you're trying to achieve, but removing the parentheses will eliminate the syntax error:

DIR_IN_Tamper

Further to it, I suspect you have similar issues with BUZZER_ON and BUZZER_OFF.

Tinatinamou

Shouldn't DIR_IN_Tamper rather be defined as a function-like macro? – Renatarenate

Maybe it should but I see the question unclear in terms of what he exactly wants to do – Greeson

@Renatarenate Maybe it should be, but, as KiaMorot pointed out, it's rather unclear from the question what the OP is trying to do. I showed one way to syntax errors. – Tinatinamou

if I remove {} it gives error error: #109: expression must have (pointer-to-) function type – Cutpurse

@user2571585: You have to remove the normal parentheses (()), not the curly braces. – Renatarenate

Answer 3

If you want to use DIR_IN_Tamper like a function, you need a function-like macro:

#define DIR_IN_Tamper()    { FIO2DIR &= ~0X00001000 ; } 

Then, a better way to do it is:

#define DIR_IN_Tamper()    do { FIO2DIR &= ~0X00001000 ; } while(0)

... but that's a different story.

Renatarenate

Yes, it is a macro. But you try to "invoke" it like a function (with ()). Therefore you need a function-like macro. – Renatarenate

macro of BUZZER_OFF is as follows- – Cutpurse

#define BUZZER_OFF() { DIR_BUZ(); B_BUZ_E(0); } – Cutpurse

do I need to remove () or {} here also..?? its not single statement but. – Cutpurse

First and foremost, you should add the definitions of the other macros to your question. – Renatarenate

If BUZZER_OFF is defined like in your comment above (function-like macro), it should just work. Otherwise, you either change the macro definition or "call" the macro without (). I rather think it is a similar problem with DIR_BUZ and/or B_BUZ_E. – Renatarenate

let us continue this discussion in chat – Cutpurse

Answer 4

Single-statement, function-like macros

Please do not use curly braces ({ and }) when defining single-statement macros like DIR_IN_Tamper.

To safely define a function-like macro, simply put your definition between parentheses, like this:

#define DIR_IN_Tamper() (FIO2DIR &= ~0X00001000)

Then, call your macro like this:

DIR_IN_Tamper();

It will behave like a functions which changes the value of FIO2DIR and then returns the changed value:

/* Your macro rewritten as a function.
   The return type should be the type of FIO2DIR */
uint32_t DIR_IN_Tamper()
{
    return (FIO2DIR &= ~0X00001000);
}

Multi-statement, function-like macros

If you ever need to define a multi-statement macro, see this other C FAQ entry.

For example, define BUZZER_OFF as:

#define BUZZER_OFF() do { DIR_BUZ(); B_BUZ_E(0); } while (0)

Schubert

Armaccess.c(973): error: #109: expression must have (pointer-to-) function type – Cutpurse

@user2571585: You have to remove the normal parentheses (()), not the curly braces. – Renatarenate

@user2571585 I commented something about {} to your question – Tarragona

I have removed () braces from main.. now it looks like BUZZER_OFF; but still error in else – Cutpurse

When in doubt, look at the pre-processed source: see https://mcmap.net/q/162838/-how-to-view-c-preprocessor-output/238421. – Schubert

Answer 5

Macros in C are not functions. DIR_IN_Tamper(); should be DIR_IN_Tamper;.

Earldom

It is like this #define DIR_IN_Tamper FIO2DIR &= ~0X00001000 & not like u have mentioned.. – Cutpurse

Huh? I mean the call. Not the macro definition. Seems you're too much confused about C. You should get a decent C book and read it before writing code. – Earldom

Then make a question about your new error, or say what error it is. – Earldom

code says as follows DIR_IN_Tamper; if(((IN_Tamper >> 12) & 0x01) == 1) BUZZER_ON; else BUZZER_OFF; where in BUZZER_OFF is again a macro defined as #define BUZZER_OFF { DIR_BUZ; B_BUZ_E(0); } since its group of statements I have used { } braces... – Cutpurse

Mu advice is that you avoid macros in C, they're more complicated and prone to errors than you might think. This explains why. – Earldom

@mOskitO never advice any one such negative thing (avoid macros in C) I got the answer when I started solving it myself. I'll share it with you- search for intermediate file in your program folder like if you have got xyz.c then search xyz.i file you will find macro expansion in there check if its there according to your logic or not. correct in program file. – Cutpurse