Delphi Performance Tip

Here's a small little Delphi performance tip that I'm not sure many people are aware of. Putting the $EXTERNALSYM after the symbol has better compiler performance than placing it before the symbol. The reason for this is pretty simple. When the compiler encounters a $EXTERNALSYM it looks for the symbol. If the symbol isn't found then it must store it and deal with it later. If the symbol is found it is used immediately.

Here's a small example:

const
  MAPVK_VK_TO_VSC    = 0;
  {$EXTERNALSYM MAPVK_VK_TO_VSC}
  MAPVK_VSC_TO_VK    = 1;
  {$EXTERNALSYM MAPVK_VSC_TO_VK}
  MAPVK_VK_TO_CHAR   = 2;
  {$EXTERNALSYM MAPVK_VK_TO_CHAR}
  MAPVK_VSC_TO_VK_EX = 3;
  {$EXTERNALSYM MAPVK_VSC_TO_VK_EX}
  MAPVK_VK_TO_VSC_EX = 4;
  {$EXTERNALSYM MAPVK_VK_TO_VSC_EX}