Gist to reproduce a AV in SynDBOra

SynDBOarAV.pas

program SynDBOarAV;

{$I Synopse.inc} // without Synopse.inc strange compiler error on line FHttpServer.OnRequest := DoOnRequest
{$define USESYN}

uses
  {.$I SynDprUses.inc} // with SynDprUses AV exists
  // cmem,             // with cmem AV exists
  cthreads,
  SynCrtSock,
  SynDB,
  {$ifdef USESYN}SynDBOracle{$ELSE}SynDBZeos{$ENDIF};

type
  { TubSQLDBOracleConnectionProperties }
  TConnectionManager = class({$ifdef USESYN}TSQLDBOracleConnectionProperties{$else}TSQLDBZEOSConnectionProperties{$endif})
  public
    function NewConnection: TSQLDBConnection; override;
  end;

  { TmySevice }
  TmySevice = class
  private
    FHttpServer: THttpServer;
    FConnectionManager: TConnectionManager;
  protected
    function DoOnRequest(Ctxt: THttpServerRequest): cardinal;
  public
    constructor Create;
    destructor Destroy; override;
  end;

{ TConnectionManager }
function TConnectionManager.NewConnection: TSQLDBConnection;
var fakeVarJustToBeAllocatedInStack: byte; // if I comment out this var (change a stack) AV disappear
begin
  //for SynDBOracle:
  // -O1 optimization: AV inside TSQLDBOracleConnection.Connect during call to EnvNlsCreate (but in real project works);
  // -O2 optimization: work as expected (but in real project AV);
  // - works for ZEOS, but I think only because of var... inside TZOracleConnection.Open
  Result:=inherited NewConnection;
end;


{ TmySevice }
constructor TmySevice.Create;
begin
  inherited Create();
  {$ifdef USESYN}
  FConnectionManager := TConnectionManager.Create('doesn''t matter', '', '', '');
  {$else}
  FConnectionManager := TConnectionManager.Create('zdbc:oracle:(doesn''t matter)?LibLocation=libclntsh.so', '', '', '');
  {$endif}
  FHttpServer := THttpServer.Create('8881', nil, nil,{HttpThreadTerminate,} 'Server', 2, 0);
  FHttpServer.OnRequest := DoOnRequest;
end;

destructor TmySevice.Destroy;
begin
  FHttpServer.Free;
  FConnectionManager.Destroy;
  inherited Destroy;
end;

function TmySevice.DoOnRequest(Ctxt: THttpServerRequest): cardinal;
var
  conn: TSQLDBConnection;
begin
  conn := FConnectionManager.ThreadSafeConnection;
  conn.Connect;
  Result := 200;
end;


begin
  with TmySevice.Create() do try
    // works in case called from main thread
    // DoOnRequest(nil);
    HttpGet('http://localhost:8881/init', nil); // call itself to create DB connection inside thread
    writeln('press Enter to stop');
    readln;
  finally
    Free;
  end;
end.