Tcl_InitStubs(3) Tcl Library Procedures Tcl_InitStubs(3) ______________________________________________________________________________
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, indicating which
minimal version of Tcl is accepted.
Normally just "8.6". Or "8.6-" if both
8.6 and 9.0 are accepted.
int exact (in) 1 means that only the particular
version specified by version is
accepted. 0 means that versions newer
than version are also accepted. If
theversion ends with -, higher major
versions are accepted as well,
otherwise the major version must be
the same as in version. Other bits
have no effect.
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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, as
long as the major Tcl version is the same.
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
standard Tcl library. For example, to use the Tcl 8.6 ABI on Unix
platforms, the library name is libtclstub8.6.a; on Windows
platforms, the library name is tclstub86.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 versions newer than version are also
accepted. If theversion ends with -, higher major versions are accepted
as well, otherwise the major version must be the same as in version. 1
means that only the specified version is accepted. version can be any
construct as described for package require (PACKAGE manual page in the
section REQUIREMENT). Multiple requirement strings like with package
require are not supported.
Tcl_InitStubs returns a string containing the actual version of Tcl
satisfying the request, or NULL if the Tcl version is not accepted,
does not support stubs, or any other error condition occurred.
SEE ALSO
Tk_InitStubs package
KEYWORDS
stubs
Tcl 8.1 Tcl_InitStubs(3)
tcl 8.6.17 - Generated Thu Aug 21 09:40:19 CDT 2025