[erlang-bugs] (unconditional) rebuild caused by gen_git_version

[Tuncer Ayaz]

On Tue, Feb 18, 2014 at 1:40 PM, Tuncer Ayaz wrote:
> Since R16 it's not possible anymore to quickly run make in a
> previously built and otherwise unmodified tree.
>
> $ make
> # everything built
> # run make again
> $ make
> ...
>  GEN    x86_64-unknown-linux-gnu/gen_git_version.mk
>  CC     obj/x86_64-unknown-linux-gnu/opt/plain/erl_bif_info.o
> ..
>  LD     /tmp/otp/master/bin/x86_64-unknown-linux-gnu/beam
>
> This doesn't take long, but recreating an object file and relinking
> the vm every time doesn't seem right to me. AFAICT, it was introduced
> to include the git revision of the tree the vm was built from.
>
> I don't have time to look into this right now, so no patch from me.

If anyone wants to submit a fix, presumably adding a check that
compares the previous build's git revision for inequality should fix
the bug. I assume it's probably already cached in a file.