Delphi in a Nutshell

Name

FreeMem Procedure

Syntax

procedure FreeMem(P: Pointer);

Description

FreeMem frees the memory that P points to. FreeMem uses the installed memory manager to free the memory. FreeMem is not a real procedure.

Tips and Tricks

• P can be nil, in which case, FreeMem returns immediately.

• When freeing memory, always take care not to free a pointer more than once, and be sure not to refer to memory after freeing it.

• To help avoid mistakes, especially in a multithreaded program, be sure to set global variables or class fields to nil before freeing the memory. You want to avoid any windows—no matter how small—where a variable or field contains an invalid pointer. For example:

procedure FreeMemAndNil(var P);
var
  Tmp: Pointer;
begin
  Tmp := Pointer(P);
  Pointer(P) := nil;
  FreeMem(Tmp);
end;

• FreeMem in Delphi’s default memory manager is thread-safe, that is, you can call FreeMem from multiple threads simultaneously, but only if IsMultiThread is True.

• Call FreeMem to free memory allocated by GetMem. Call Dispose to free memory allocated by New.

See Also

Dispose Procedure, IsMultiThread Variable, GetMem Procedure, ReallocMem Procedure, SetMemoryManager Procedure, SysFreeMem Function