Is there a -Dmacro like option for D compilers?

[ryuukk_]

On Monday, 27 March 2023 at 22:22:26 UTC, Jeremy wrote:
> Is there a way I can define a manifest constant from the 
> compiler command-line, like the -Dmacro option for C compilers?

You can do this way:


```
dmd -version=FEATURE_A
```

```D

import std.stdio;

void main()
{

     version(FEATURE_A)
     {
         writeln("feature A enabled");
     }

}

```

Unfortunatly there is not #ifndef, so in case you want to make 
sure FEATURE_A is not there you'll have to do:

```D

import std.stdio;

void main()
{

     version(FEATURE_A)
     {}
     else
     {
         writeln("feature A not available");
     }

}

```


or

```D

import std.stdio;


version(FEATURE_A)
{
     enum FEATURE_A_AVAILABLE = true;
}
else
{
     enum FEATURE_A_AVAILABLE = false;
}

void main()
{
     static if (!FEATURE_A_AVAILABLE)
     {
         writeln("feature A not available");
     }

}

```


For some reason they force us to be overly verbose

Or it's possible to do it, but i don't know much more than this 
about ``-version``


(if you use ldc compiler, it's ``-d-version=``)