delphi - Delayed DLL directive causing application deadlock on FireDAC query -


i have application set in following manner in delphi xe5:

main.exe: calls function in sub.dll using export delayed directive

function myfunction: boolean; external 'sub.dll' delayed;

sub.dll: contains firedac query object runs simple select query.

upon opening query, delayed directive application not terminate when main form closed (process main.exe remains in task manager). process explorer shows thread remaining sub.dll. main.exe process terminates correctly when not specify delayed directive. missing? feel i'm not freeing object can't figure out is.

simplified code:

main.exe:

program main;  {$apptype console}  {$r *.res}  uses   system.sysutils;    function myfunction: boolean; external 'sub.dll' delayed;  begin   try     myfunction;   except     on e: exception begin       writeln(e.classname, ': ', e.message);       readln;     end;   end; end.

sub.dll

library sub;  uses   system.sysutils,   system.classes,   dbconn in 'dbconn.pas';  {$r *.res}  function myfunction: boolean; export; var conn: tconn; begin   conn := tconn.create;   conn.destroy;   result := true; end;  exports   myfunction;  begin end.

dbconn.pas

unit dbconn;  interface  uses   firedac.stan.intf, firedac.stan.option,   firedac.stan.error, firedac.ui.intf, firedac.phys.intf, firedac.stan.def,   firedac.phys, firedac.stan.pool, firedac.stan.async, firedac.stan.param,   firedac.dats, firedac.dapt.intf, firedac.dapt, firedac.vclui.wait,   firedac.comp.ui, firedac.phys.odbcbase, firedac.phys.asa, data.db,   firedac.comp.dataset, firedac.comp.client;  type   tconn = class     fdconnection: tfdconnection;     fdquery: tfdquery;      constructor create;     destructor destroy; override;   end;  var   conn: tconn;  { tconn }  implementation  constructor tconn.create; begin   fdconnection := tfdconnection.create(nil);   //set database connection parameters   fdconnection begin     close; params.clear;     params.add('driverid=asa');     params.add('database=');     params.add('server=');     params.add('user_name=');     params.add('password=');     open;   end;   fdquery := tfdquery.create(nil);   fdquery begin     connection := fdconnection;     close; unprepare; sql.clear;     sql.add('select first last_name');     sql.add('from users');     sql.add('order last_name');     prepare; open; //this causes deadlock     writeln(output, fieldbyname('last_name').asstring);   end; end;  destructor tconn.destroy; begin   fdconnection.close;   fdconnection.free;   inherited; end;  end.

this firedac limitation. see http://docwiki.embarcadero.com/radstudio/xe8/en/dll_development_(firedac)#firedac_dll_unloading


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