Tcl_InitStubs(3)					      Tcl Library Procedures						  Tcl_InitStubs(3)

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NAME

       Tcl_InitStubs - initialize the Tcl stubs mechanism

SYNOPSIS

       #include <tcl.h>

       const char *
       Tcl_InitStubs(interp, version, exact)

ARGUMENTS

       Tcl_Interp *interp (in)		Tcl interpreter handle.

       const char *version (in) 	A version string consisting of one or more decimal numbers separated by dots.

       int exact (in)			Non-zero  means that only the particular version specified by version is acceptable.  Zero means that ver-
					sions newer than version are also acceptable as long as they have the same major version  number  as  ver-
					sion.
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INTRODUCTION

       The  Tcl  stubs	mechanism  defines a way to dynamically bind extensions to a particular Tcl implementation at run time.  This provides two
       significant benefits to Tcl users:

       1)   Extensions that use the stubs mechanism can be loaded into multiple versions of Tcl without being recompiled or relinked.

       2)   Extensions that use the stubs mechanism can be dynamically loaded into statically-linked Tcl applications.

       The stubs mechanism accomplishes this by exporting function tables that define an interface to the Tcl API.  The  extension  then  accesses
       the Tcl API through offsets into the function table, so there are no direct references to any of the Tcl library's symbols.  This redirect-
       ion is transparent to the extension, so an extension writer can continue to use all public Tcl functions as documented.

       The stubs mechanism requires no changes to applications incorporating Tcl interpreters.	Only developers creating  C-based  Tcl	extensions
       need to take steps to use the stubs mechanism with their extensions.

       Enabling the stubs mechanism for an extension requires the following steps:

       1)   Call Tcl_InitStubs in the extension before calling any other Tcl functions.

       2)   Define the USE_TCL_STUBS symbol.  Typically, you would include the -DUSE_TCL_STUBS flag when compiling the extension.

       3)   Link  the  extension  with	the  Tcl  stubs library instead of the standard Tcl library.  On Unix platforms, the library name is libt-
	    clstub8.1.a; on Windows platforms, the library name is tclstub81.lib.

       If the extension also requires the Tk API, it must also call Tk_InitStubs to initialize the Tk stubs interface and link with the  Tk  stubs
       libraries.  See the Tk_InitStubs page for more information.

DESCRIPTION

       Tcl_InitStubs  attempts	to  initialize	the  stub  table pointers and ensure that the correct version of Tcl is loaded.  In addition to an
       interpreter handle, it accepts as arguments a version number and a Boolean flag indicating whether the extension requires an exact  version
       match  or  not.	 If  exact  is 0, then the extension is indicating that newer versions of Tcl are acceptable as long as they have the same
       major version number as version; non-zero means that only the specified version is acceptable.  Tcl_InitStubs returns a	string	containing
       the  actual version of Tcl satisfying the request, or NULL if the Tcl version is not acceptable, does not support stubs, or any other error
       condition occurred.

SEE ALSO

       Tk_InitStubs

KEYWORDS

       stubs

Tcl									8.1							  Tcl_InitStubs(3)