This is not necessarily the current version of this TIP.
|Version:||$Revision: 1.4 $|
|Author:||Kevin Kenny <kevin dot b dot kenny at gmail dot com>|
|Created:||Thursday, 01 October 2009|
This TIP proposes to promote the internal calls, TclLoadFile and TclpFindSymbol to the external API, making them available to C extensions. In addition, it proposes to introduce a Tcl_FSUnloadFile to the VFS layer, removing the weird duplicate client data from TclLoadFile and wrapping all necessary data into the Tcl_LoadHandle.
In developing TDBC, the author of this TIP was advised to look at the way that the 'oratcl' extension contrives to build on a system where Oracle is not installed as a model for TDBC extensions. Examination of the code revealed that it operates essentially by constructing at run time a Stubs table for the routines in the Oracle client library. There is a maze of #if directives selecting whether this process is accomplished by the system calls that manage Unix .so files (dlopen and friends), Windows .DLL files (LoadLibrary and related calls), HP-UX .shl files (shl_load, etc.), and so on.
Tcl already has functionality so that a caller can abstract away all this complexity. It provides the capability in the TclLoadFile call, but this call is MODULE_SCOPE and not exported even in the internal Stubs table. For this reason, it is entirely unavailable to TEA-compliant extensions.
If this call were available, it would be feasible, in the 8.6 time frame, to bundle all the database-specific TDBC drivers with the core TDBC distribution, since things could be set up so that they will build anywhere, even in the absence of the databases where they connect.
However, this call was never fully rationalized in the VFS world. Its strange API (with both a Tcl_LoadHandle and a ClientData, and a function pointer for unloading the library) is, as several reviewers pointed out, not somehting that we want to make available to general callers. Hence, a few more routines need rework.
The TclLoadFile call shall be renamed Tcl_LoadFile and exported in the external Stubs. Its call signature shall be changed to:
EXTERN int Tcl_LoadFile( Tcl_Interp *interp