From Newsgroup: comp.lang.tcl

Is there a cross platform way to tell if a tcl build is a 32-bit or 64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits, respectively. Is this the way to go?

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From Newsgroup: comp.lang.tcl


saito <[email protected]> posted:

Is there a cross platform way to tell if a tcl build is a 32-bit or 64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits, respectively. Is this the way to go?

It has worked for me for Windows 7 32bit and Windows 10 and 11 64bit . Catching
an error when loading a 32bit extension could be more accurate and
it works for any OS ?

Olivier.
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From Newsgroup: comp.lang.tcl

Am 14.09.2026 um 15:49 schrieb saito:

Is there a cross platform way to tell if a tcl build is a 32-bit or 64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits, respectively. Is this the way to go?

Yes, pointerSize is the way, at least on MS-Win.
And what about:

package require platform
platform::generic

There is no "_64" suffix when compiled for 32 bit on a 64 bit platform.
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From Newsgroup: comp.lang.tcl

* saito <[email protected]>
| tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
| both cases.

https://www.tcl-lang.org/man/tcl/TclCmd/tclvars.html

tcl_platform(wordsize) is documented as the result of sizeof(long),
which is 4 only on Windows for both 32 and 64 bits.
On 64-bit Linux, tcl_platform(wordsize) is 8:

$ tclsh
% parray tcl_platform
tcl_platform(machine) = x86_64
tcl_platform(os) = Linux
tcl_platform(osVersion) = 6.12.107+deb13-amd64
tcl_platform(platform) = unix
tcl_platform(pointerSize) = 8
tcl_platform(wordSize) = 8
[...]

| tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits,
| respectively.

tcl_platform(pointerSize) is the result of sizeof(void*) (aka pointer
size), which is the closest you get (most likely '4' for 32-bit OSes and
'8' for 64-bit OSes).

The question would be why it matters to your code?

R'
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From Newsgroup: comp.lang.tcl

On 9/14/2026 9:49 AM, saito wrote:

Is there a cross platform way to tell if a tcl build is a 32-bit or 64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits, respectively. Is this the way to go?

Thanks to all for the replies. So the consensus is to use the
pointerSize attribute.


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From Newsgroup: comp.lang.tcl

Am 14.09.26 um 22:09 schrieb saito:

On 9/14/2026 9:49 AM, saito wrote:

Is there a cross platform way to tell if a tcl build is a 32-bit or
64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-bits,
respectively. Is this the way to go?

Thanks to all for the replies. So the consensus is to use the
pointerSize attribute.

Use whatever you need. That's also my question, what do you need this information for?

pointerSize gives you the size of the adressable memory. wordSize gives
you the size of a long. Those are not necessarily the same - on Win64
bit, long is 32 bit and void* 64 bit, whereas on Linux, both are 64 bit.
When you write all of your code in Tcl, wordSize does not matter much,
because it has bigInts. For interfacing with C subroutines that use Tcl_GetLongFromObj(), those will accept different ranges. Usually, you
should not need either of them (in a perfect world).

Christian
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From Newsgroup: comp.lang.tcl

On 9/14/2026 4:46 PM, Christian Gollwitzer wrote:

Am 14.09.26 um 22:09 schrieb saito:

On 9/14/2026 9:49 AM, saito wrote:

Is there a cross platform way to tell if a tcl build is a 32-bit or
64-bit?

tcl_platform(wordsize) doesn't seem to be reliable as it reports 4 in
both cases. tcl_platform(pointerSize) reports 4 and 8 for 32-/64-
bits, respectively. Is this the way to go?

Thanks to all for the replies. So the consensus is to use the
pointerSize attribute.

Use whatever you need.

Well, "whatever" doesn't work. For example, wordSize returns the same
number for me on both 32-bit and 64 bit on the same PC.

That's also my question, what do you need this
information for?

More of an idle curiosity over tcl_platform than anything else at this
point, though there are instances when that could be useful. Python has
an explicit function for this called sys.maxsize. If larger than 2**32,
it is 64 bits.


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From Newsgroup: comp.lang.tcl

On 9/14/2026 12:10 PM, Ralf Fassel wrote:

https://www.tcl-lang.org/man/tcl/TclCmd/tclvars.html

Thanks for this link.
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From Newsgroup: comp.lang.tcl

* saito <[email protected]>
| Python has an explicit function for this called sys.maxsize. If larger
| than 2**32, it is 64 bits.

I think all you can deduce from "> 2**32" is that it's larger than 32
bits (eg could be 128 bits). It is the same problem as in "if it is
larger than 32768, it's 32 bits". That was probably mostly true some
decades ago when the change from 16 to 32 bits was made, but no longer
today.

I would go with Haralds' suggestion and check for the trailing "*64" in [platform::generic].

https://www.tcl-lang.org/man/tcl/TclCmd/platform.html

DESCRIPTION
The platform package provides several utility commands useful for the
identification of the architecture of a machine running Tcl.


Keep in mind that even on a 64-bit OS, a 32-bit build of TCL still has "pointersize 4" and "*ix86" in platform::generic.

R'
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