[fpc-pascal] Use environment variables in configuration file?

[Michael Van Canneyt]

On Wed, 29 Jan 2014, Michael Van Canneyt wrote:

>
>
> On Wed, 29 Jan 2014, hinst wrote:
>
>> I want to use an environment variable in FPC configuration file; is this 
>> not possible?
>> I created sample project which demonstrates the problem. I have one main 
>> source file and one unit which is located
>> in subdirectory.
>> I try to compile my program with this bash script:
>>  
>> It looks like FPC does not substitute $mvar with meow. It does not compile 
>> my program.
>> However if I change options variable to this:
>> options="@cfg.txt -Mobjfpc pro.pas -Fu$mvar"
>> Then my program gets compiled successfully.
>
> Obviously, since the bash interpreter takes care of substitution, FPC never 
> sees $mvar.
>
>
>> It means that:
>>   If I put -Fu$mvar in config file then it does not work
>>   If I put -Fu$mvar in bash script then it does work
>>  
>> Which is strange because in standard config file fpc.cfg I can find not 
>> only built-in variables like $FPCVERSION but
>> also environment variables like $LOCAL_APPDATA
>>  
>> Examples:
>> -FuD:\Lazarus\fpc\$FPCVERSION/units/$fpctarget/httpd22
>> -Fu$LOCAL_APPDATA\FreePascal\fppkg/units/$FPCTARGET/*
>> This I do not understand. How come that FPC when reading config file 
>> understands $LOCAL_APPDATA, but does not
>> substitute variable I specified $mvar
>
> Because there are several standard "placeholders" that FPC understands in the 
> config file. These placeholders start with $.
> They are not environment variables, despite the notation with $.

See globals.pas

          ReplaceSpecialFolder('$LOCAL_APPDATA',CSIDL_LOCAL_APPDATA);
          ReplaceSpecialFolder('$APPDATA',CSIDL_APPDATA);
          ReplaceSpecialFolder('$COMMON_APPDATA',CSIDL_COMMON_APPDATA);
          ReplaceSpecialFolder('$PERSONAL',CSIDL_PERSONAL);
          ReplaceSpecialFolder('$PROGRAM_FILES',CSIDL_PROGRAM_FILES);
          ReplaceSpecialFolder('$PROGRAM_FILES_COMMON',CSIDL_PROGRAM_FILES_COMMON);
          ReplaceSpecialFolder('$PROFILE',CSIDL_PROFILE);

Is the standard list on Windows.

And looking a bit further, I just see that you CAN do environment variables,
if you enclose them in $$, so $mvar$ would do the trick.

Michael.