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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 particu-
					lar version specified  by  version  is
					acceptable.   Zero means that versions
					newer than version are also acceptable
					as  long  as  they have	the same major
					version	number as version.
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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 signif-
       icant benefits to Tcl users:

       1)   Extensions that use	the stubs mechanism can	be loaded into	multi-
	    ple	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	redirection 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 stan-
	    dard  Tcl  library.	  For  example,	to use the Tcl 8.6 ABI on Unix
	    platforms, the library name	is libtclstub8.6.a; on	Windows	 plat-
	    forms, the library name is tclstub86.lib.

       If  the	extension also requires	the Tk API, it must also call Tk_Init-
       Stubs 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	inter-
       preter  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 ver-
       sion  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)

NAME | SYNOPSIS | ARGUMENTS | INTRODUCTION | DESCRIPTION | SEE ALSO | KEYWORDS

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