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[C question] Best way to change features of the program at compile time: #if((n)def) or if (const)? (kbin.social)

submitted 2 years ago* (last edited 2 years ago) by [email protected] to c/[email protected]

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Suppose that I have two features in my C program, feature foo and feature bar. I wish to be able to switch what features will be compiled into my program at compile time. The only two ways I know of doing this are:

Using preprocessor directives

#define MYPROG_FEATURE_FOO 1
#define MYPROG_FEATURE_BAR 1

/* ... */

#if MYPROG_FEATURE_FOO == 1
/* code related to feature foo */
#else
/* code to prompt people to pay for the absolutely proprietary version of my program */
#endif

/* ... */

#if MYPROG_FEATURE_BAR == 1
/* code related to feature bar */
#else
/* code to prompt people to pay for the absolutely proprietary version of my program */
#endif

/* ... */

Using the normal if with a const, non-volatile variable

const _Bool myprog_feature_foo = 1;
const _Bool myprog_feature_bar = 1;

/* ... */

if (myprog_feature_foo)
{
  /* code related to feature foo */
}
else
{
  /* buy proprietary version or no feature for you >:) */
}

/* ... */

if (myprog_feature_bar)
{
  /* code related to feature bar */
}
else
{
  /* buy proprietary version or no feature for you >:) */
}

/* ... */

What's the better way to do this? Is there a third way to achieve this that I have missed that's better than the above two?

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[–] qtip 1 points 2 years ago

Where appropriate, I split code like this into separate files (I like to have similarly named files in separate directories) with multiple build configurations. I'll tell the build system to compile different files for each configuration. I like this because it keeps the code clean and avoids using the preprocessor