On Thu, 10 Aug 2017, Ximin Luo wrote:
> Normally, system-wide CFLAGS etc are a static expression of policy. What I
> by that is, writing logic to determine CFLAGS for particular package, would
> "look like" the actual wording of that policy. So for example, "all packages
> should have debug" => "CFLAGS+=-g", "packages that match property X should
> flag Y" => "if X then CFLAGS += Y". OTOH if your policy is "packages should be
> reproducible" and we have to add these prefix-remapping flags to CFLAGS,
> adding a dependency from the value of CFLAGS itself, onto the build-time
> filesystem. So CFLAGS is no longer a static expression of policy, it depends
> information not part of the policy.
> So, prefix-map is really different from other CFLAGS, it adds extra dependency
> relationships that other flags don't add.
I think the difference is essentially that these options belong in CC not
CFLAGS (CFLAGS is for non-semantic options, CC should include any options
that are required in every compilation).
(FWIW, I support having the environment variable, but think there should
be some command-line option exactly equivalent to it.)
Joseph S. Myers