TIP 484: Merge 'int' and 'wideInt' Obj-type to a single 'int'

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Author:         Jan Nijtmans <jan.nijtmans@gmail.com>
State:          Final
Type:           Project
Vote:           Done
Created:        06-Nov-2017
Post-History:
Keywords:       Tcl
Tcl-Version:    8.7
Tcl-Branch:     no-wideint

Abstract

The 'wideInt' type was invented for Tcl because the 'int' type (which was actually 'long') was not sufficient to store numbers larger than [+-]2**31. This TIP proposes to merge the 'int' and the 'wideInt' Obj-types such that 'int' does all internal calculations using Tcl_WideInt in stead of long.

Rationale

For linux64, the 'wideInt' type doesn't give any advantage, it is #ifdef'd out in the code. For Windows 64, since 'long' is the same as 'int', it would be an advantage to use __int64 for all internal number processing. Since __int64 calculations are just as efficient as int/long calculations on most (64-bit and 32-bit) processors, it would save all kinds of range checks in the Tcl code. That's the main gain of this TIP.

Finally, for 32-bit systems, getting rid of 'int' could give a small disadvantage on systems which split 64-bit calculations in terms of 32-bit calculations. There 32-bit calculations could become slightly slower.

Since the gain for 64-bit platforms (mainly Win64) is expected to be more than the possible loss on some 32-bit system, I still propose to follow this road.

Another advantage of this change is maintainability of number handling. Currently the C code contains a lot of #ifdef's which check whether sizeof(long) is the same a sizeof(wideint). Most of those checks can be removed, so the number handling becomes almost identical on all platforms supported by Tcl.

Proposal

Merge 'int' and 'wideInt' Obj-type to a single 'int'. Make the following changes:

Compatibility

Starting with Tcl 9.0:

On systems where sizeof(Tcl_WideInt) != sizeof(long)

No test-cases are modified in the 'no-wideint' branch, all current test-cases continue to pass. This shows that separating the 'int' and the 'wideInt' implementation is nowhere required to let Tcl number handling function the way it functions now. At the script level, the change is invisible.

Reference Implementation

An implementation of this TIP can be found in the no-wideint branch.

The code is licensed under the same license as Tcl.

Caveats

Some examples (the only 3 I found):

Rejected Alternatives

Copyright

This document has been placed in the public domain.