suppressing the compilation of the block of code

Given something like the following

Code:

---

#include <stdio.h>
#include <stdlib.h>

int main( void )
{
    FILE *fp;
    int c1,
    char c2;

    if ( ( fp = fopen( "test.txt", "r" ) == NULL )
    {
        fprintf( stderr, "Failed to open file\n" );
        return EXIT_FAILURE;
    }

    /* Read until nothing can be read anymore */

    while ( ( c1 = fgetc( fp ) ) != EOF )
        putchar( c1 );

#if 0
    /* or, when using fscanf() */

    while ( fscanf( fp, "%c", &c2 ) == 1 )
        putc( c2 )

    /* or, when using fread() */

    while ( fread( &c2, 1, 1, fp ) == 1 )
        putc( c2 )
#endif

    /* Check why the last read failed */

    if ( feof( fp ) )
        fprintf( stderr, "End of file detected\n" );
    else
        fprintf( stderr, "Read error\n" );

#if 0
    /* or using ferror() */

    if ( ferror( fp ) )
        fprintf( stderr, "Read error\n" );
    else
        fprintf( stderr, "End of file detected\n" );
#endif

    close( fp );
    return 0;
}

---

Is there a particular advantage to suppressing the compilation a block of code vs suppressing the execution of the block ?

Yes, if the size of the executable is to be reduced. Also, some piece of code might require linking of other files which can also be removed by conditional compilation.

Quote:

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Is there a particular advantage to suppressing the compilation a block of code vs suppressing the execution of the block ?

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There is also perforamnce issue. If you leave a condition in the code - that is checked in runtime - it still takes some CPU cycles... Moreover - if you compiler is not too good - you will have possible branch misprediction on this condition check - that can greately decrease performance of the code...

If this part of the code lies in some very frequently called function - it can result in big performance difference of the resulting code comaring to the code that has removed that part on the compilation stage