stdenv: Add isPc helper to replace (isi686 || isx86_64)

[dezgeg]

It's a relatively common operation to compare the current platform to PC platforms, i.e. x86 compatible platforms.

Bikeshedding: maybe there's a better name than isPc?

[codyopel]

x86 would be more accurate then pc

[wmertens]

isIA? isIntelArch?

On Fri, May 15, 2015, 7:36 AM Cody Opel notifications@github.com wrote:

x86 would be more accurate then pc

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#7846 (comment).

[edolstra]

isX86 is probably the most accurate. isIntelArch isn't since there are other Intel architectures (Itanium, i960, ...).

[vcunat]

@edolstra: Why "isX86" and not "isx86" when we have "isx86_64"?

[edolstra]

camelCase dictates starting a non-initial word with a capital letter. So isx86_64 is wrong.

[vcunat]

So, the situation is to choose any two from: consistency, camelCase rule, and backward compatibility?

[wmertens]

No we can also fix all the isx86_64 occurrences, and we can add aliases as
well :)

On Fri, May 15, 2015 at 10:58 AM Vladimír Čunát notifications@github.com
wrote:

So, the situation is to choose any two from: consistency, camelCase rule,
and backward compatibility?

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#7846 (comment).

[wmertens]

other options for that one are isX8664 (6 capitalized is 6) or isX86-64 or
is-x86_64 (nix forging new ground with - in names)

On Fri, May 15, 2015 at 12:55 PM Wout Mertens wout.mertens@gmail.com
wrote:

No we can also fix all the isx86_64 occurrences, and we can add aliases as
well :)

On Fri, May 15, 2015 at 10:58 AM Vladimír Čunát notifications@github.com
wrote:

So, the situation is to choose any two from: consistency, camelCase rule,
and backward compatibility?

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#7846 (comment).

[vcunat]

Yes, dash is probably more common, so isX86-64 and isX86, and perhaps also isI686 to fix camelCase? If we're doing big renames, we should choose carefully. We might also keep the old names as deprecated aliases for some time to keep compatibility. @edolstra, others?

[edolstra]

Please no dashes in variable names!

[vcunat]

I'm just curious, why should only package attributes use dashes?

[copumpkin]

The shed should be purple!!!

[codyopel]

An idea I had for simplify things would be use something like:

isX86    # All x86 variations
isX86_32 # x86 32bit (i{3,4,5,6,7}86)
isX86_64 # x86 64bit (amd64)
isARM    # All ARM variations
isARM_32 # ARM 32bit (armv{5,6,7,8,+})
isARM_64 # ARM 64bit (armv{8,+})
...
isMIPS
isMIPS_32
isMIPS_64
isPPC
isPPC_32
isPPC_64
isSPARC
isSPARC_32
isSPARC_64

This would use a generic base identifier (X86) and then add on _32 & _64 for specifying Bits. x86_32 would be less politically correct than using i686, but might help to avoid confusion. Obviously some of these listed are not necessary since Nix doesn't support some of the listed arch's or variations there of.

[vcunat]

IMO the name i686 implies that the HW shouldn't be too old and e.g. support MMX and some other features.

For a long time I meant to ask why we have various functions for platform categorization in lib/systems.nix and then in stdenv we just redefine the same groups without using the previous implementation. Perhaps I misunderstand the purpose of systems.nix.

[dezgeg]

Changed to isX86.