"Acess violation" when using a scripted constant - inno-setup

Question

I need to implement a scripted constant to retrieve a drive of user-selected path.
I tried the code bellow, but I'm getting:
Acess violation ate adress 0043D8E0.Read of address 01CDE694
[Code]
procedure InitializeWizard;
begin
Page := CreateInputDirPage(
wpSelectDir,'Select local', 'Where will be stored?', '', False, 'New Folder');
Page.Add('Local Dserver (APP)');
Page.Add('Local Images (Storage)');
Page.Values[0] := ('F:\TEST1');
Page.Values[1] := ('G:\TEST2');
end;
function ExtractFileDrive(const FileName: string): String;
begin
Result := ExtractFileDrive(Page.Values[0]);
end;
[Run]
Filename: {code:ExtractFileDrive|0}\postgresql-9.4.5-1-windows-x64.exe

Answer 1

Your ExtractFileDrive scripted constant shadows the ExtractFileDrive support function. So you recursively call your ExtractFileDrive function from itself ad infinitum, until the stack overflows.
Just rename your function to anything else.
And once doing that, rename its argument, as the FileName is confusing. And also remove the scripted constant parameter in its use, as you actually do not use it.
[Code]
function GetFileDrive(Param: string): String;
begin
Result := ExtractFileDrive(Page.Values[0]);
end;
[Run]
Filename: {code:GetFileDrive}\postgresql-9.4.5-1-windows-x64.exe