[fpc-pascal] Redirecting input to a child process

[Anton Shepelev]

Ludo Brands:

> You can file a bug at http://bugs.freepascal.org/.

This is bug #0019325.

...
I thought about writing a patch, but it seems that it is not
enough to modify the implementation of the  Windows-specific
pipes.inc.

The correct way to create pipes for the three channels (out,
in and err) on Windows is to create non-inheritable  handles
and  duplicate  only  the  child process's ends of them into
inheritable ones, which  means  that  the  CreatePipeHandles
function  must accept a third parameter indicating which end
should be inherited: for OUT and ERR channels it will be the
write-end and for IN -- the read-end.

Here is a possible implementation:

{--------------- changes to pipes.inc -----------------}
Interface
   {...}
   type
      TDupOpt  = (dupIn, dupOut);
      TDupOpts = Set of TDupOpt;

Implemenation
   {...}
   function DuplicateHandleFP(var handle: THandle): Boolean;
   var
      oldHandle: THandle;
   begin
      oldHandle := handle;
      Result := DuplicateHandle
      (  GetCurrentProcess(),
         oldHandle,
         GetCurrentProcess(),
         @handle,
         0,
         true,
         DUPLICATE_SAME_ACCESS
      );
      if Result then
         Result := CloseHandle(oldHandle);
   end;

   Function CreatePipeHandles
   (Var Inhandle,OutHandle : THandle; DupOpts: TDupOpts) : Boolean;
   begin
      Result := CreatePipe (Inhandle,OutHandle, at piNonInheritablePipe,0);
      if Result and (dupIn in DupOpts) then
         Result := DuplicateHandleFP(Inhandle);
      if Result and (dupOut in DupOpts) then
         Result := DuplicateHandleFP(OutHandle);
   end;

   {----------- process.inc -------------------------}
   {CreatePipes will have these calls:}
   begin
     CreatePipeHandles(SI.hStdInput ,HI, [dupIn ]);
     CreatePipeHandles(HO,Si.hStdOutput, [dupOut]);
     if CE then
       CreatePipeHandles(HE,SI.hStdError, [dupOut])
   {...}

Unfortunately,  the third parameter will have to be added to
this  function  in  all  other  platform-specific  pipes.inc
files, but these will just ignore it and work as before.

If  it is preferable to keep the interface of the pipes unit
unchanged, the windows-specific part could just be chaged to
create  non-inheritable  pipes, and the duplication could be
moved into the windows-specific process.inc.

Will you accept one of such patches?

Anton