From: Mike Frysinger <vapier@gentoo.org>
To: Jon Turney <jon.turney@dronecode.org.uk>
Cc: "newlib@sourceware.org" <newlib@sourceware.org>
Subject: Re: [PATCH v2] newlib: libm: merge build up a directory
Date: Mon, 21 Feb 2022 13:30:04 -0500 [thread overview]
Message-ID: <YhPaLPjMnQ7jpYcE@vapier> (raw)
In-Reply-To: <5dc5d2ce-668b-49ac-bbf4-bbf0cdcb3da7@dronecode.org.uk>
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On 21 Feb 2022 18:04, Jon Turney wrote:
> On 21/02/2022 18:00, Mike Frysinger wrote:
> > On 21 Feb 2022 12:20, Corinna Vinschen wrote:
> >> On Feb 16 23:42, Mike Frysinger wrote:
> >>> Convert all the libm/ subdir makes into the top-level Makefile. This
> >>> allows us to build all of libm from the top Makefile without using any
> >>> recursive make calls. This is faster and avoids the funky lib.a logic
> >>> where we unpack subdir archives to repack into a single libm.a. The
> >>> machine override logic is maintained though by way of Makefile include
> >>> ordering, and source file accumulation in libm_a_SOURCES.
> >>>
> >>> One thing to note is that this will require GNU Make because of:
> >>> libm_a_CFLAGS = ... $(libm_a_CFLAGS_$(subst /,_,$(@D)))
> >>> This was the only way I could find to supporting per-dir compiler
> >>> settings, and I couldn't find a POSIX compatible way of transforming
> >>> the variable content. I don't think this is a big deal as other
> >>> Makefiles in the tree are using GNU Make-specific syntax, but I call
> >>> this out as it's the only one so far in the new automake code that
> >>> I've been writing.
> >>>
> >>> Automake doesn't provide precise control over the output object names
> >>> (by design). This is fine by default as we get consistent names in all
> >>> the subdirs: libm_a-<source>.o. But this relies on using the same set
> >>> of compiler flags for all objects. We currently compile libm/common/
> >>> with different optimizations than the rest.
> >>>
> >>> If we want to compile objects differently, we can create an intermediate
> >>> archive with the subset of objects with unique flags, and then add those
> >>> objects to the main archive. But Automake will use a different prefix
> >>> for the objects, and thus we can't rely on ordering to override.
> >>>
> >>> But if we leverage $@, we can turn Automake's CFLAGS into a multiplex
> >>> on a per-dir (and even per-file if we wanted) basis. Unfortunately,
> >>> since $@ contains /, Automake complains it's an invalid name. While
> >>> GNU Make supports this, it's a POSIX extension, so Automake flags it.
> >>> Using $(subst) avoids the Automake warning to get a POSIX compliant
> >>> name, albeit with a GNU Make extension.
> >>> ---
> >>> v2
> >>> - rebased onto latest tree
> >>> - fixed a parallel build issue with generated newlib headers & libm objects
> >>
> >> This patch breaks Cygwin. Unfortunately I didn't try to build myself,
> >> but only inspected the patch, so I didn't realize the problem.
> >>
> >> First of all, Cygwin takes libm.a from newlib/libm/, not from newlib.
> >> This is easily fixable.
> >>
> >> However, even after fixing this, we get a link stage error for *all*
> >> fenv functions:
> >>
> >> ld: x86_64-pc-cygwin/newlib/libm.a(libm_a-fenv.o): in function `fegetenv':
> >> newlib/libm/machine/x86_64/../shared_x86/fenv.c:160:
> >> multiple definition of `fegetenv';
> >> x86_64-pc-cygwin/newlib/libm.a(libm_a-fegetenv.o):
> >> newlib/libm/fenv/fegetenv.c:65:
> >> first defined here
> >>
> >> For some reason, libm.a contains both definitions of the fenv functions,
> >> the x86_64 definitions from newlib/libm/machine/shared_x86, as well as
> >> the fallback definitions from newlib/libm/fenv.
> >>
> >> Can you please take a look?
> >
> > how do you build cygwin ? i've just been doing w/newlib-cygwin git checkout:
> > $ ./configure --target=i686-pc-cygwin && make
> > $ ./configure --target=x86_64-pc-cygwin && make
> > these are passing for me
>
> You'll need to apply this patch:
>
> https://cygwin.com/pipermail/cygwin-patches/2022q1/011766.html
>
> Otherwise, you are linking with a stale libm.a left in your builddir
> from before these changes.
while i often test incremental changes, i `rm -rf` the build dir when running
the full test suite to avoid possible issues like this. and in this case,
both targets pass from a fresh build.
-mike
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next prev parent reply other threads:[~2022-02-21 18:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-12 20:34 [PATCH] " Mike Frysinger
2022-02-16 8:50 ` [HEADSUP] " Corinna Vinschen
2022-02-16 9:40 ` Sebastian Huber
2022-02-16 10:48 ` Corinna Vinschen
2022-02-17 4:38 ` Mike Frysinger
2022-02-17 4:42 ` [PATCH v2] " Mike Frysinger
2022-02-17 12:08 ` Corinna Vinschen
2022-02-21 11:20 ` Corinna Vinschen
2022-02-21 18:00 ` Mike Frysinger
2022-02-21 18:04 ` Jon Turney
2022-02-21 18:30 ` Mike Frysinger [this message]
2022-02-21 19:12 ` Jon Turney
2022-02-21 19:24 ` Corinna Vinschen
2022-02-21 20:30 ` Mike Frysinger
2022-02-21 20:31 ` Mike Frysinger
2022-02-21 18:28 ` Mike Frysinger
2022-02-21 20:43 ` [PATCH] newlib: libm: workaround ar duplicate member behavior Mike Frysinger
2022-02-21 20:51 ` Joel Sherrill
2022-02-21 22:12 ` Mike Frysinger
2022-02-21 22:14 ` Joel Sherrill
2022-02-22 0:21 ` [PATCH v2] " Mike Frysinger
2022-02-22 11:31 ` Corinna Vinschen
2022-02-22 12:34 ` Jon Turney
2022-02-22 17:17 ` Mike Frysinger
2022-02-23 8:56 ` Corinna Vinschen
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