path: root/open_issues/gcc.mdwn

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[[!tag open_issue_gcc]]

Here's what's to be done for maintaining GCC.

Apart from the target-specific configuration machinery, there shouldn't be any
major differences within GCC between the GNU/Hurd and GNU/Linux ports, for
example.  Especially all the compiler magic is all the same.

[[!toc levels=2]]


# [[General information|/gcc]]


# [[Sources|source_repositories/gcc]]


## Boehm GC

GCC includes an own variant of [[/Boehm_GC]] that is based on an upstream
version, but with own patches, etc.  This is used for Java.  (There are patches
(apparently not committed) that GCC itself can use it, too:
<http://gcc.gnu.org/wiki/Garbage_collection_tuning>.)

Patches to GCC's fork should be contributed back to upstream [[/Boehm_GC]].

[[tschwinge]] reviewed (but only briefly for large parts) the differences on
2010-12-08, based on the [[GCC Git mirror's
8e79e9d43f32c8852f068da91d655297d92ac0f4 (2010-11-29)
sources|source_repositories/GCC]] and Boehm GC's CVS HEAD sources from
2010-12-02, converted to [[Git, correspondingly
1c2455988a8f59a5f83b986b9156f03be395b3b6|source_repositories/boehm_gc]].

On 2010-11-17,
[[tschwinge]] reviewed the Debian GCC Boehm GC changes, compared them to the
upstream code, and put it into the local *hurd/boehm-gc/config_backport*
branch, planning to submit it to gcc-patches after testing with the GCC
testsuite.


# Configuration

Last reviewed up to the [[Git mirror's 3457702eb6f8ee22acaee881dc7f783c3aa2fa91
(2010-12-08) sources|source_repositories/gcc]].

<http://gcc.gnu.org/install/configure.html> has documentation for the
`configure` switches.

  * Configure fragments that have `*linux*` cases might/should often contain
    those for us (and GNU/k*BSD) as well.

      * `configure.ac`

      * `libgcc/configure.ac` [might
        need](http://gcc.gnu.org/ml/gcc-patches/2008-10/msg00315.html) to be
        aligned for us to the `*linux*` cases.  As well as at the end of
        `libgcc/config.host`.  Check.

            checking whether decimal floating point is supported... no
            checking whether fixed-point is supported... no

      * `libgomp/configure.tgt`

      * Etc.

  * [[`libmudflap`|libmudflap]].

  * Might [`-fsplit-stack`](http://nickclifton.livejournal.com/6889.html) be
    worthwhile w.r.t. our multithreaded libraries?

  * <http://gcc.gnu.org/ml/gcc/2007-11/msg00289.html>,
    <http://gcc.gnu.org/ml/gcc-patches/2010-12/msg00672.html>

  * `--enable-languages=[...]`

      * GNAT is not yet ported / bootstrapped?

      * The Google Go's libgo (introduced in
        e440a3286bc89368b8d3a8fd6accd47191790bf2 (2010-12-03)) apparently needs
        OS configuration / support.

  * `--enable-frame-pointer`

    `gcc/configure.ac`: `enable_frame_pointer=no`

  * `--with-dwarf2`?

  * `--enable-werror`

  * `--enable-checking`

  * `--enable-build-with-cxx`

  * `--enable-decimal-float`, `--enable-fixed-point`, `--with-long-double-128`

    `configure: WARNING: decimal float is not supported for this target,
    ignored`

  * `--enable-linker-build-id`

  * `--enable-gnu-unique-object`

  * `--enable-lto`, `--enable-gold`

    [[binutils_gold]]

  * `--enable-indirect-function`

    [[IFUNC]]


# TODO

Debian's GCC package has Hurd-specific patches.  Some have been forwarded
upstream (and have been ignored).  [[Thomas_Schwinge|tschwinge]] is working on
getting them integrated.

  * [\[meta-bug\] bootstrap bugs for
    \*-gnu\*](http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21824)

  * [build system: gcc\_cv\_libc\_provides\_ssp and
    NATIVE\_SYSTEM\_HEADER\_DIR](http://gcc.gnu.org/ml/gcc/2008-10/msg00130.html)

  * [-fstack-protector shouldn't use TLS in freestanding
    mode](http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29838)

  * [Tool chain configuration: GNU/\* sharing stuff with
    GNU/Linux](http://gcc.gnu.org/ml/gcc/2007-11/msg00289.html)


# Build

Here's a log of a GCC build run; this is from our [[Git repository's
5ac39af7792ba0dc363cc199060faf53dfa9dc1a (2010-12-08)
sources|source_repositories/gcc]], run on kepler.SCHWINGE and grubber.

    $ export LC_ALL=C
    $ ../master/configure --prefix="$PWD".install 2>&1 | tee log_build
    [...]
    $ make SHELL=/bin/bash 2>&1 | tee log_build_
    [...]

(kepler.SCHWINGE defaults to using /bin/sh, grubber to /bin/bash; thus
harmonized.)

On grubber, this needs roughly 24 hours, and takes up around 2.5 GiB.


## Analysis

    $ diff -wu <(ssh kepler.SCHWINGE 'cd tmp/source/gcc/ && cat hurd/master.build/log_build* | sed -e "s%${PWD}%[...]%g"' | sed -f open_issues/gcc/log_build-linux.sed) <(ssh grubber 'cd tmp/gcc/ && cat hurd/master.build/log_build* | sed "s%${PWD}%[...]%g"' | sed -f open_issues/gcc/log_build-hurd.sed) > open_issues/gcc/log_build-diff

[[log_build-diff]].

  * [[`checking if gcc static flag -static
    works... no`|glibc_madvise_vs_static_linking]]

  * DFP

        +configure: WARNING: decimal float is not supported for this target, ignored

    ... and later on:

        -checking for decimal floating point... bid
        +checking for decimal floating point... configure: WARNING: decimal float is not supported for this target, ignored
        +dpd

    ... and later on:

        -checking whether decimal floating point is supported... yes
        +checking whether decimal floating point is supported... no
        +configure: WARNING: decimal float is not supported for this target, ignored

  * `host-linux.c` vs. `host-default.c`

  * *fixincludes* stuff

  * malloc?

        -cat ../../hurd/gcc/config/i386/pmm_malloc.h > mm_malloc.h
        +cat ../../hurd/gcc/config/i386/gmm_malloc.h > mm_malloc.h

  * *libgomp*

      * `libgomp/config/linux/`, `libgomp/config/linux/x86`

      * `-ftls-model=initial-exec -march=i486 -mtune=i686`

  * `-static` vs. `dlopen`

        -checking whether a statically linked program can dlopen itself... no
        +checking whether a statically linked program can dlopen itself... yes

  * ISO/IEC TR 24733

        -checking for ISO/IEC TR 24733 ... yes
        +checking for ISO/IEC TR 24733 ... no

  * `basic_file.cc`

        +basic_file.cc: In member function 'std::streamsize std::__basic_file<char>::showmanyc()':
        +basic_file.cc:344:33: warning: enumeral and non-enumeral type in conditional expression [enabled by default]

  * `libtool: link: ar rc .libs/libstdc++.a [...]`

    Just different order of object files, or another problem?

  * `gcc/gthr-posix.h`

        +In file included from ../.././gcc/gthr-default.h:1:0,
        +                 from [...]/hurd/libobjc/../gcc/gthr.h:162,
        +                 from [...]/hurd/libobjc/thr.c:43:
        +[...]/hurd/libobjc/../gcc/gthr-posix.h: In function '__gthread_objc_thread_set_priority':
        +[...]/hurd/libobjc/../gcc/gthr-posix.h:384:41: warning: unused parameter 'priority' [-Wunused-parameter]

  * `java-signal.h`, `java-signal-aux.h`

        -config.status: linking ../../../hurd/libjava/include/i386-signal.h to include/java-signal.h
        -config.status: linking ../../../hurd/libjava/include/i386-signal.h to include/java-signal-aux.h
        +config.status: linking ../../../hurd/libjava/include/default-signal.h to include/java-signal.h
        +config.status: linking ../../../hurd/libjava/include/default-signal.h to include/java-signal-aux.h

  * `jni_md.h`

        -checking jni_md.h support... yes
        +checking jni_md.h support... configure: WARNING: no

  * *default library search path*

        -checking for the default library search path... /lib /usr/lib /lib/i486-linux-gnu /usr/lib/i486-linux-gnu /usr/local/lib 
        +checking for the default library search path... /lib /usr/lib

  * `./classpath/[...]/*.properties`

    Just different order of files, or another problem?

  * `libjava/gnu/gcj/util/natGCInfo.cc`

        +../../../hurd/libjava/gnu/gcj/util/natGCInfo.cc:440:1: warning: unused parameter 'name' [-Wunused-parameter]
        +../../../hurd/libjava/gnu/gcj/util/natGCInfo.cc:446:1: warning: unused parameter 'name' [-Wunused-parameter]
        +../../../hurd/libjava/gnu/gcj/util/natGCInfo.cc:452:1: warning: unused parameter 'name' [-Wunused-parameter]

  * `gnu/java/net/natPlainSocketImpl.cc`

        +gnu/java/net/natPlainSocketImpl.cc: In member function 'virtual jint gnu::java::net::PlainSocketImpl::available()':
        +gnu/java/net/natPlainSocketImpl.cc:515:27: warning: enumeral and non-enumeral type in conditional expression [enabled by default]

  * `gnu/java/nio/channels/natFileChannelImpl.cc`

        +gnu/java/nio/channels/natFileChannelImpl.cc: In member function 'jint gnu::java::nio::channels::FileChannelImpl::available()':
        +gnu/java/nio/channels/natFileChannelImpl.cc:388:20: warning: enumeral and non-enumeral type in conditional expression [enabled by default]

  * `libgcj.la`, `.libs/libgcj.a`

    Just different order of object files, or another problem?

    Is there a pattern that GNU/Hurd hands out the files alphabetically sorted
    where it wouldn't need to ([[!taglink open_issue_hurd]])?

    Why does the GNU Hurd's `lib_build_` repeatedly contain a long series
    (several KiB) of NUL (0) characters after the 5319th column in the
    `/bin/bash ./libtool --tag=CXX --mode=link [...] -o libgcj.la [...]`
    command line?  Is that only in the log?

  * `libjvm.la`, `.libs/libjvm.so`, `libgij.la`, `.libs/libgij.so.12.0.0`

    `-Wl,-Bsymbolic` vs. `-Wl,-Bsymbolic-functions`


# Install

    $ make SHELL=/bin/bash install 2>&1 | tee log_install
    [...]

(kepler.SCHWINGE defaults to using /bin/sh, grubber to /bin/bash; thus
harmonized.)

On grubber, this needs roughly 15 minutes, and takes up around 0.7 GiB.


## Analysis

    $ diff -wu <(ssh kepler.SCHWINGE 'cd tmp/source/gcc/ && cat hurd/master.build/log_install | sed -e "s%${PWD}%[...]%g" -e "s%i686-pc-linux-gnu%[ARCH]%g"') <(ssh grubber 'cd tmp/gcc/ && cat hurd/master.build/log_install | sed -e "s%${PWD}%[...]%g" -e "s%i686-unknown-gnu0\.3%[ARCH]%g"') > open_issues/gcc/log_install-diff

[[log_install-diff]].

  * `libtool: finish`: `ldconfig` is not run for the Hurd.

  * `libjvm.la`, `.libs/libjvm.so`, `libgij.la`, `.libs/libgij.so.12.0.0`

    `-Wl,-Bsymbolic` vs. `-Wl,-Bsymbolic-functions` (as above)


# Testsuite

<http://gcc.gnu.org/install/test.html>

    $ make SHELL=/bin/bash -k check 2>&1 | tee log_check
    [...]

Blocked on [[fork_mach_port_mod_refs_ekern_urefs_owerflow]].


## Analysis