#55884: mandoc @1.14.3: not using the right compiler

[Jan Stary]

On Feb 28 08:03:31, ken.cunningham.webuse at gmail.com wrote:
> The basic principle is that a build of a port on any darwin_N system
> anywhere will be identical to every other build on that darwin version
> on all other machines.

Does that mean that MP will set the same configure.cc for mandoc
on e.g. every Darwin 17.4.0? What of I have two of those,
with different Xcode on each?

Can you please indly point me to the place in MP base
where the value of configure.cc get decided?

> To do that, but build environment (and the runtime environment)
> need to be fully pre-defined.

As long as it's possible to have different Xcode versions on one darwin_N,
in what sense can the build environment be "fully pre-defined"? For example,
https://trac.macports.org/wiki/UsingTheRightCompiler says:

	 For example, with Xcode 4.2 and later, CC is set to
	 "/usr/bin/clang" so that there is no ambiguity.

"/usr/bin/clang" will be a different compiler with Xcode 4.2
and with Xcode 4.N


> See here: <https://reproducible-builds.org/> for more info,
> and why this is what we need. I hope you can come to accept
> some of these MacPorts policies

This makes sense, unlike what's being said at
https://trac.macports.org/wiki/UsingTheRightCompiler

Are these policies clearly described somewhere?


On Feb 28 10:20:56, ryandesign at macports.org wrote:
> >> I had my MacPorts configured to error out if `cc` is used
> >> using the method described at  UsingTheRightCompiler#testing.
> > 
> > Why would you do that?
> 
> To detect ports that do not use a specific compiler.
> MacPorts policy is that all ports shall use a specific compiler.

Is this policy described somewhere?

> > BTW, this is how configure.cc is described in the guide:
> > 
> >  configure.cc
> >    Set CC compiler flags for selecting a C compiler.
> >    Default: ???
> >    Example:
> > 
> > "compiler flags for selecting a compiler"?
> 
> Rainer has now adjusted these descriptions in the guide.

https://guide.macports.org/chunked/reference.phases.html still says
"Set CC compiler flags for selecting a C compiler."


On Feb 28 17:36:38, raimue at macports.org wrote:
> On 2018-02-28 08:52, Jan Stary wrote:
> > The ticket is closed, so I will continue here.
> > 
> >>  Actually it's not specific to the universal variant. Rather, the problem
> >>  is that the port is not UsingTheRightCompiler.
> > 
> > mandoc's ./configure sets CC to whatever make(1) thinks CC is:
> > CC=`printf "all:\\n\\t at echo \\\$(CC)\\n" | env -i make -sf -`
> > Why exactly is it "not the right compiler"?
> 
> As env -i clears the environment,
> how is this supposed to work at all?
> This does not respect CC in the environment, which is what MacPorts
> usually does.
> 
> $ export CC=foo
> $ printf "all:\\n\\t at echo \\\$(CC)\\n" | env -i make -sf -
> cc

That's on purpose: compile mandoc with
whatever the local make(1) thinks $(CC) is.

  # You can manually override the compiler to be used.
  # But that's rarely useful because ./configure asks your make(1)
  # which compiler to use, and that answer will hardly be wrong.

mandoc's ./configure does not take CC from the environment.
It determines it as above. You can override it of course,
by setting CC=... in configure.local

That seems to be the issue here: MP _wants_to_ tell mandoc what compiler
to use, but setting CC in the environment does not do it. Hence the CC
dance that we have in the Portfile now. Is this understanding correct?


> > It's true that /usr/bin/cc is a symlink to some suitable default compiler.
> > So call that, thus calling a suitable default compiler, _by_default_.
> 
> You are already assuming that 'cc' is /usr/bin/cc. If anyone has a
> /opt/local/bin/cc, it might be a different compiler.

If it is actually a C compiler, it will compile mandoc just fine.
If it is instead a shell script that errors out with "you must not run
this as your compiler", then it will not of course.

> In general, we do not want to use what the user selected as their
> preferred compiler, but what MacPorts selected to compile this port.

Is this strict policy clearly described somewhere, including the
rationale? Not in https://trac.macports.org/wiki/UsingTheRightCompiler

> > Yes, there are ports that do need to call some particular compiler,
> > but it's those ports' job then to find and use that.

> >> I had my MacPorts configured to error out if `cc` is used
> >> using the method described at  UsingTheRightCompiler#testing.
> > 
> > Why would you do that?
> >
> > Mandoc is extremely portable. I have yet to see a UNIX system where
> > it does not build. Except here: of course it "breaks" if you explicitly
> > make it impossible to run 'cc', which is the right compiler.
> 
> This setup is a good idea for developers to catch ports that are not
> respecting the environment variables for compiler selection.

This seems to confirm that this is what's "wrong" with mandoc in this
respect - it does not listen to MP's CC setting and has to be told
explicitly.

> Looks like an old copy & paste mistake to me. I committed a fix. [1]
> Ryan was even faster to notice than me typing this mail. :-)
> 
> >> Perhaps the portfile code that set `CC`
> >>  that was removed in [14f7de9e9ad521cce6389678675706e8593b9834/macports-
> >>  ports] was needed after all.
> > 
> > It is only "needed" if you make it artificially impossible
> > to call 'cc' (or whatever the port ./configures to be CC).
> > 
> > So: because ports must not call 'cc' on your system,
> > let's complicate the mandoc Portfile for everyone.
> 
> Build systems are supposed to follow CC in the environment.

This would be much easier to get if this was
written somewhere in the guide. Can we please have
https://trac.macports.org/wiki/UsingTheRightCompiler
incorporated in the Guide, with carefuly worded rationale,
explicitly stating those policies? Maybe somewhere in
https://guide.macports.org/index.html#development.practices ?
That seems to be my whole misunderstanding.

(Maybe start with a better title. An excelent piece of extremely portable
software such as mandoc, that compiles just anywhere - and brings its own
compat_strtonum() in case the system doesn't have it - is being accused
right off of 'not using the right compiler'. Like, uh, 'cc').

> The whole
> point of options like configure.cc is that they are respected when
> building the port.

There is a similar setting in mandoc's Portfile now for INSTALL.
Is there also sucha thing as 'the right installer'? As in,
a specific install(1)? Is that needed?

> As an alternative to pass compiler in environment variables would be
> generating wrapper scripts that use the right compiler as selected by
> MacPorts. This is the way other projects like Fink do it. Then the usual
> names cc/gcc/clang/... will always end up at the intended binary by
> putting them to the front of PATH. However, this is a long-standing
> issue and I am not aware anyone was working on this. Therefore, build
> systems still need to be patched to honor CC from the environment.

OK, I think I get it now. Thank you.

	Jan