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Tcl_InitStubs(3) Tcl Library Procedures Tcl_InitStubs(3)
Tcl_InitStubs - initialize the Tcl stubs mechanism
const char *
Tcl_InitStubs(interp, version, exact)
Tcl_Interp *interp (in) Tcl interpreter handle.
const char *version (in) A version string consisting of one or
more decimal numbers separated by
int exact (in) Non-zero means that only the
particular 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
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 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
1) Call Tcl_InitStubs in the extension before calling any other Tcl
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.
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
Tcl 8.1 Tcl_InitStubs(3)