Hello, people!

I would like to have a constant with the value of some environment variable that is defined at compile time.

In FreePascal, it can be done by defining it in source as:

VALUE_OF_SOMETHING = {$I %SOMETHING%};

And I can call the compiler with (bash):

SOMETHING='Anything' export SOMETHING; <compiler> <flags>

And it will automatically assign VALUE_OF_SOMETHING to 'Anything'.


In GCC C compiler, the solution I found was more complicated but it worked.

I had to explicitly define the environment variable when calling the compiler with:

gcc <flags> -DSOMETHING=\""Anything"\" -o <output> <source_file>


Now, I would like to do that with the 'dmd' compiler.

I know I could possibly use 'gdc' to achieve that but I want to use the 'dmd' compiler.

Is it possible to do that such a thing or through source or any other means?


Thank you!

On Mon, 10 Dec 2018 11:08:23 +0000, Narxa wrote:
> Hello, people!
> 
> I would like to have a constant with the value of some environment variable that is defined at compile time.

In your build script, echo the environment variable into a file. Then import() that file and use the value.

> I know I could possibly use 'gdc' to achieve that but I want to use the 'dmd' compiler.

Defining variables like that is a language-level feature. gdc supports exactly the same options as dmd.

On Monday, 10 December 2018 at 11:08:23 UTC, Narxa wrote:
> Hello, people!
>
> I would like to have a constant with the value of some environment variable that is defined at compile time.
>
> In FreePascal, it can be done by defining it in source as:
>
> VALUE_OF_SOMETHING = {$I %SOMETHING%};
>
> And I can call the compiler with (bash):
>
> SOMETHING='Anything' export SOMETHING; <compiler> <flags>
>
> And it will automatically assign VALUE_OF_SOMETHING to 'Anything'.
>
>
> In GCC C compiler, the solution I found was more complicated but it worked.
>
> I had to explicitly define the environment variable when calling the compiler with:
>
> gcc <flags> -DSOMETHING=\""Anything"\" -o <output> <source_file>
>
>
> Now, I would like to do that with the 'dmd' compiler.
>
> I know I could possibly use 'gdc' to achieve that but I want to use the 'dmd' compiler.
>
> Is it possible to do that such a thing or through source or any other means?
>
>
> Thank you!

I don't know if it's possible but one way to do it would be to use the -J switch and give it a config file that has contents:

VAR1=Value1
VAR2=Value2

And then in source code:

immutable config = import("config");
mixin(parseConfig);

string parseConfig(string str) {
  string ret;
  foreach (line; str.split("\n")) {
    auto parts = line.split("=");
    ret ~= `string ` ~ parts[0] ~ ` = "` parts[2] `";`;
  }
  return ret;
}

You can also echo out the config file with bash or something

Cheers,
- Ali

On Monday, 10 December 2018 at 17:47:37 UTC, Neia Neutuladh wrote:
> On Mon, 10 Dec 2018 11:08:23 +0000, Narxa wrote:
>> Hello, people!
>> 
>> I would like to have a constant with the value of some environment variable that is defined at compile time.
>
> In your build script, echo the environment variable into a file. Then import() that file and use the value.
>
>> I know I could possibly use 'gdc' to achieve that but I want to use the 'dmd' compiler.
>
> Defining variables like that is a language-level feature. gdc supports exactly the same options as dmd.

It worked!

Thank you very much!

On Mon, 10 Dec 2018 17:58:32 +0000, aliak wrote:
> string parseConfig(string str) {
>    string ret;
>    foreach (line; str.split("\n")) {
>      auto parts = line.split("=");
>      ret ~= `string ` ~ parts[0] ~ ` = "` parts[2] `";`;
>    }
>    return ret;
> }

That works as long as none of the environment variable values contain a double quote or a newline character.