Tcl_RegisterConfig(interp, pkgName, configuration, valEncoding)
The function described here has its base in TIP 59 and provides
extensions with support for the embedding of configuration
information into their binary library and the generation of a
Tcl-level interface for querying this information.
To embed configuration information into their binary library an
extension has to define a non-volatile array of Tcl_Config entries in
one if its source files and then call Tcl_RegisterConfig to
register that information.
Tcl_RegisterConfig takes four arguments; first, a reference to
the interpreter we are registering the information with, second, the
name of the package registering its configuration information, third,
a pointer to an array of structures, and fourth a string declaring the
encoding used by the configuration values.
The string valEncoding contains the name of an encoding known to
Tcl. All these names are use only characters in the ASCII subset of
UTF-8 and are thus implicitly in the UTF-8 encoding. It is expected
that keys are legible English text and therefore using the ASCII
subset of UTF-8. In other words, they are expected to be in UTF-8
too. The values associated with the keys can be any string
however. For these the contents of valEncoding define which
encoding was used to represent the characters of the strings.
Each element of the configuration array refers to two strings
containing the key and the value associated with that key. The end of
the array is signaled by either an empty key or a key identical to
NULL. The function makes no copy of the configuration
array. This means that the caller has to make sure that the memory
holding this array is never released. This is the meaning behind the
word non-volatile used earlier. The easiest way to accomplish
this is to define a global static array of Tcl_Config entries. See the file
in the sources of the Tcl core for an example.
When called Tcl_RegisterConfig will
create a namespace having the provided pkgName, if not yet
create the command pkgconfig in that namespace and link it to
the provided information so that the keys from _configuration_ and
their associated values can be retrieved through calls to
The command pkgconfig will provide two subcommands, list
Returns a list containing the names of all defined keys.
::pkgName::pkgconfig get key
Returns the configuration value associated with the specified