[Bug lto/54206] New: build in source dir breaks lto plugin detection

[Bug lto/54206] New: build in source dir breaks lto plugin detection

[andi-gcc at firstfloor dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

             Bug #: 54206
           Summary: build in source dir breaks lto plugin detection
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andi-gcc@firstfloor.org


when building inside the source dir with a plugin ld that supports plugin
this check in gcc/configure.ac fails

AC_MSG_CHECKING(linker plugin support)
gcc_cv_lto_plugin=0
if test -f liblto_plugin.la; then


Result is a compiler without ld plugin support

It works with a separate build dir

Should either handle this or error out on in tree builds

[Bug lto/54206] build in source dir breaks lto plugin detection

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-08-09
                 CC|                            |steven at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-09 08:31:14 UTC ---
Confirmed. But from http://gcc.gnu.org/install/configure.html:

First, we *highly* recommend that GCC be built into a separate directory from
the sources which does not reside within the source tree. This is how we
generally build GCC; building where srcdir == objdir should still work, but
doesn't get extensive testing; building where objdir is a subdirectory of
srcdir is unsupported. 

So WONTFIX is tempting...

[Bug lto/54206] build in source dir breaks lto plugin detection

[andi-gcc at firstfloor dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

--- Comment #2 from Andi Kleen <andi-gcc at firstfloor dot org> 2012-08-09 12:39:14 UTC ---
I didn't do it, but I had to debug a user's gcc config who did it.

WONTFIX would be wrong, if you really don't support it error out in configure
please instead of silent breakage (glibc does that).
But fixing it would be better I think.

[Bug lto/54206] build in source dir breaks lto plugin detection

[matt at godbolt dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

Matt Godbolt <matt at godbolt dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matt at godbolt dot org

--- Comment #3 from Matt Godbolt <matt at godbolt dot org> 2012-10-04 18:10:55 UTC ---
I've just hit this problem too after a large amount (for me!) of debugging the
build process of GCC. A big +1 to either fixing it "properly" (however that may
be achieved), or completely deprecating the srcdir==objdir build so people like
myself and Andi don't get waylaid for a long time diagnosing the issue.

[Bug lto/54206] build in source dir breaks lto plugin detection

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aoliva at gcc dot gnu.org,
                   |                            |bonzini at gnu dot org, dj
                   |                            |at redhat dot com,
                   |                            |Ralf.Wildenhues at gmx dot
                   |                            |de

--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2012-10-04 18:44:16 UTC ---
(In reply to comment #3)
> I've just hit this problem too after a large amount (for me!) of debugging the
> build process of GCC. A big +1 to either fixing it "properly" (however that may
> be achieved), or completely deprecating the srcdir==objdir build so people like
> myself and Andi don't get waylaid for a long time diagnosing the issue.

Nobody is even thinking about fixing it ever, so I wonder why keep punishing
users.

It would be extra nice to detect that objdir is a subdirectory of srcdir and
give a nice error.

[Bug lto/54206] build in source dir breaks lto plugin detection

[andi-gcc at firstfloor dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

--- Comment #5 from Andi Kleen <andi-gcc at firstfloor dot org> 2012-10-04 18:50:52 UTC ---
This is the configure snippet glibc is using for this.
Someone with better autoconf-fu than me could add it


if test "`cd $srcdir; /bin/pwd`" = "`/bin/pwd`"; then
  AC_MSG_ERROR([you must configure in a separate build directory])
fi

[Bug lto/54206] build in source dir breaks lto plugin detection

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-10-04 19:04:56 UTC ---
Build directory as subdirectory of the build directory works just fine, I'm
using it for more than a decade, it is just srcdir == builddir that is broken
and not supported.

[Bug lto/54206] build in source dir breaks lto plugin detection

[bonzini at gnu dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

--- Comment #7 from Paolo Bonzini <bonzini at gnu dot org> 2012-10-05 06:33:41 UTC ---
Building in srcdir usually works.  Could it be as simple as this?

Index: Makefile.am
===================================================================
--- Makefile.am    (revisione 177688)
+++ Makefile.am    (copia locale)
@@ -12,7 +12,7 @@ AM_CFLAGS = @ac_lto_plugin_warn_cflags@
 AM_LIBTOOLFLAGS = --tag=disable-static

 libexecsub_LTLIBRARIES = liblto_plugin.la
-gcc_build_dir = ../$(host_subdir)/gcc
+gcc_build_dir = ../gcc
 in_gcc_libs = $(foreach lib, $(libexecsub_LTLIBRARIES),
$(gcc_build_dir)/$(lib))

 # Can be removed when libiberty becomes a normal convenience library

[Bug lto/54206] build in source dir breaks lto plugin detection

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 62260 which is fixed for GCC 5.

*** This bug has been marked as a duplicate of bug 62260 ***