...get source code location information?

Use GetLocationInfo function from EDebugInfo unit:

uses
  ELowLevel,  // for GetEIP
  EClasses,   // for TELLocationInfo
  EDebugInfo; // for GetLocationInfo
 
procedure Test;
begin
 
end;
 
procedure TForm1.Button1Click(Sender: TObject);
var
  Info: TELLocationInfo;
begin
  // Get information about arbitrary code location
  Info := GetLocationInfo(@Test);

  // Once information is obtained - you can use it
  Label1.Caption := Info.UnitName + '.' + Info.ProcedureName;
  // Will output: 'Unit1.Test'

  // Get information about current location
  Info := GetLocationInfo(GetEIP);

  Label2.Caption := Info.UnitName + '.' + Info.ProcedureName;
  // Will output: 'Unit1.Button1Click'
end;

If you need information about current location only - you can also use simple wrappers: __MODULE__, __UNIT__, __FILE__, __FUNCTION__, and __LINE__. For example:

uses
  EDebugInfo; // for __FILE__, __FUNCTION__, __LINE__
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  Log('Entering ' + __FILE__ + ' ' + __FUNCTION__ + ' ' + __LINE__);

  // Will log 'Entering Unit1.pas TForm1.Button1Click 42'

  // Real code goes below

  // ...

end;

Please note that it is better to use a proper logging.

See also: