Gforth Manual
14.2.2 Direct or Indirect Threaded?
Both! After packaging the nasty details in macro definitions we
realized that we could switch between direct and indirect threading by
simply setting a compilation flag (-DDIRECT_THREADED) and
defining a few machine-specific macros for the direct-threading case.
On the Forth level we also offer access words that hide the
differences between the threading methods (see section 5.24 Threading Words).
Indirect threading is implemented completely machine-independently.
Direct threading needs routines for creating jumps to the executable
code (e.g. to docol or dodoes). These routines are inherently
machine-dependent, but they do not amount to many source lines. Therefore,
even porting direct threading to a new machine requires little effort.
The default threading method is machine-dependent. You can enforce a
specific threading method when building Gforth with the configuration
flag --enable-direct-threaded or
--enable-indirect-threaded. Note that direct threading is not
supported on all machines.
