Why is this C macro causing syntax error?

Question

This is the first time I'm using macros in C and I'm trying to replace a large section of code that I'd normally place into a function with a macro. This is a part of an interrupt which will be used quite often and therefore I need to optimize it as much as I can. After reading the documentation, I've seen that the compiler doesn't support function inlining and I want to avoid the function call overhead.

The code itself sends data to a serial-in parallel-out shift register and as far as I can see, there's no shorter way to write the piece of code I need.

I'm using C18 compiler version 3.41 and MPLAB X IDE.

So here's the code I'm using in function form:

void first_one(void)
{
   //3 invisible zeroes
            LATBbits.LATB1=0; //data set to zero

            LATBbits.LATB0=1;//first clock
            LATBbits.LATB0=0;

            LATBbits.LATB0=1;//second clock
            LATBbits.LATB0=0;

            LATBbits.LATB0=1;//third clock
            LATBbits.LATB0=0;
            //end of invisible zeroes

            //two visible zeroes    
            LATBbits.LATB0=1;//first clock
            LATBbits.LATB0=0;

            LATBbits.LATB0=1;//second clock
            LATBbits.LATB0=0;
            //end of two visible zeroes

            LATBbits.LATB1=1;//Data is now one

            LATBbits.LATB0=1;
            LATBbits.LATB0=0;
            //one 

            LATBbits.LATB1=0;//Data is now zero

            LATBbits.LATB0=1;//first clock
            LATBbits.LATB0=0;

            LATBbits.LATB0=1;//second clock
            LATBbits.LATB0=0;

            //after this, everything should be in place
            LATBbits.LATB0=1;
            LATBbits.LATB0=0;
}

I've turned the function into this macro:

#define first_one() {  \
\
            LATBbits.LATB1=0;\               
                              \
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
                                \
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
                            \
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
            \                                
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
\
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
            \
            LATBbits.LATB1=1;\
\
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\    
\
            LATBbits.LATB1=0;\
             ^^^ The syntax error is here!
\
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
\
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
\
            LATBbits.LATB0=1;\
            LATBbits.LATB0=0;\
\
                     }

So what am I doing wrong?

Update: I removed the comments and am now getting a syntax error in a different location.

Answer 1

Check there is no spaces after the \ tokens, some compiler issue a compile error for this.