Re: 32-bit host vs 64-bit host

[Grant Edwards <grant.b.edwards@gmail.com>]

On 2014-02-25, <roman@kolesnikov.mobi> <roman@kolesnikov.mobi> wrote:

>>What sort of differences did you find?
>
> I could not compile the standard c library with the 32 bit toolchain on
> a 64 bit host, when the same library would build fine on the 32 bit
> host. I have ran into this issue many times during the second stage of
> the toolchain build on a 64 bit host. Same gcc/glibc sources would
> compile on a 32 bit host but would fail on a 64 bit. 

Ah, I see. I suspect that has something to do with missing 32-bit
compatibility libraries.  That's not really what I'm asking about.

I've got a 32-bit toolchain which has been in use for some time on
both 32-bit and 64-bit hosts -- everything works fine.

The last of the 32-bit machines in the development group was just
changed over to 64-bit.  Now everybody is running 64-bit development
machines.  I'm trying to decide how much testing and verification would
be needed if/when we rebuild the exact same toolchain as a 64-bit
hosted application.

For a naively written compiler (e.g. all of the one's I've
written/worked on), I would expect the exact same object code to be
emitted regardless of the word-size of the host.  However, gcc is far
from "naive" and I wouldn't put it past the developers to write
optimizer code that actually generates different output when the
host's native word size changes.

One of these days, I'll build a toolchain on a 64-bit host and
actually compare some target program binaries to see if anything
changes...

-- 
Grant Edwards               grant.b.edwards        Yow! Now I'm concentrating
                                  at               on a specific tank battle
                              gmail.com            toward the end of World
                                                   War II!


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