[Bug c++/53650] New: large array causes huge memory use

[Bug c++/53650] New: large array causes huge memory use

[david at doublewise dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

             Bug #: 53650
           Summary: large array causes huge memory use
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: david@doublewise.net


This problem did not exist in 4.6.x. The following program uses > 4 GiB of
memory (more than my system has) during compilation. If I reduce the size of
the array a bit, it still uses several GiB but does eventually compile (so the
problem is not infinite recursion) and takes a very long time to compile.
Compiling with optimizations on seems to eliminate the large memory usage but
takes longer than I was willing to wait to compile.

class Class {
public:
    Class() {}
};

int main() {
    Class table [2048][256] = {};
    return 0;
}


Using something like int causes no problems and compiles quickly.

This may also relate to a C++11 missed optimization opportunity, because this
may suggest that the fact that Class has a constructor is making it non-POD,
but the POD rules were relaxed in C++11 to make Class a POD structure (I
think). Compiling with std=c++11 doesn't fix the problem, however.

gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/4.7.0/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --disable-build-with-cxx
--disable-build-poststage1-with-cxx --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada,go,lto --enable-plugin
--enable-initfini-array --enable-java-awt=gtk --disable-dssi
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib
--with-ppl --with-cloog --with-tune=generic --with-arch_32=i686
--build=x86_64-redhat-linux
Thread model: posix
gcc version 4.7.0 20120507 (Red Hat 4.7.0-5) (GCC)

[Bug c++/53650] large array causes huge memory use

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-06-13
                 CC|                            |jason at redhat dot com
   Target Milestone|---                         |4.7.2
     Ever Confirmed|0                           |1

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> 2012-06-13 04:58:35 UTC ---
It is caused by revision 180944:

http://gcc.gnu.org/ml/gcc-cvs/2011-11/msg00230.html

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[david at doublewise dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

David Stone <david at doublewise dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |david at doublewise dot net

--- Comment #2 from David Stone <david at doublewise dot net> 2012-06-13 18:44:18 UTC ---
Turns out that contrary to my previous report, optimizations don't actually
solve the memory use problem, they just slow it down significantly. Several
hours into compilation, memory use was at ~2 GiB and still growing (very
slowly). It seems that maybe it uses just as much memory, it just takes much,
much longer to get there.

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Jason Merrill <jason at gcc dot gnu.org> changed:

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

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> 2012-06-14 06:18:41 UTC ---
(In reply to comment #1)
> It is caused by revision 180944:

Specifically, the "Don't use build_aggr_init for aggregate initialization of
arrays." part.

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |slbyan at gmail dot com

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-14 08:37:34 UTC ---
*** Bug 53666 has been marked as a duplicate of this bug. ***

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[david at doublewise dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

--- Comment #5 from David Stone <david at doublewise dot net> 2012-06-17 19:54:52 UTC ---
As a workaround for this bug, I was able to compile much faster (so that I can
compile my program with optimizations turned on) by declaring the constructor
for the class in the array as constexpr (which worked just fine for me because
I only cared that a single member variable was 0, and the rest could have
indeterminate values).

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.2                       |4.7.3

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-20 10:15:58 UTC ---
GCC 4.7.2 has been released.

[Bug c++/53650] [4.7/4.8 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-03 16:51:51 UTC ---
Author: jason
Date: Thu Jan  3 16:51:41 2013
New Revision: 194860

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=194860
Log:
    PR c++/53650
    * call.c (type_has_extended_temps): New.
    * cp-tree.h: Declare it.
    * decl.c (check_initializer): Use build_aggr_init for arrays
    if it is false.
    * init.c (build_vec_init): Avoid mixed signed/unsigned arithmetic.

Added:
    trunk/gcc/testsuite/g++.dg/init/array34.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/decl.c
    trunk/gcc/cp/init.c

[Bug c++/53650] [4.7 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.7/4.8 Regression] large  |[4.7 Regression] large
                   |array causes huge memory    |array causes huge memory
                   |use                         |use

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-03 16:53:36 UTC ---
Fixed for 4.8 so far.  Waiting a bit before applying the fix to 4.7.

[Bug c++/53650] [4.7 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-22 16:29:07 UTC ---
Author: jason
Date: Tue Jan 22 16:28:58 2013
New Revision: 195380

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=195380
Log:
    PR c++/53650
    * call.c (type_has_extended_temps): New.
    * cp-tree.h: Declare it.
    * decl.c (check_initializer): Use build_aggr_init for arrays
    if it is false.
    * init.c (build_vec_init): Avoid mixed signed/unsigned arithmetic.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/init/array34.C
Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/call.c
    branches/gcc-4_7-branch/gcc/cp/cp-tree.h
    branches/gcc-4_7-branch/gcc/cp/decl.c
    branches/gcc-4_7-branch/gcc/cp/init.c

[Bug c++/53650] [4.7 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #10 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-22 16:34:20 UTC ---
Fixed.

[Bug c++/53650] [4.7 Regression] large array causes huge memory use

[pluto at agmk dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

Pawel Sikora <pluto at agmk dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pluto at agmk dot net

--- Comment #11 from Pawel Sikora <pluto at agmk dot net> 2013-01-22 21:05:45 UTC ---
(In reply to comment #9)
> Author: jason
> Date: Tue Jan 22 16:28:58 2013
> New Revision: 195380
> 
> URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=195380
> Log:
>     PR c++/53650
>     * call.c (type_has_extended_temps): New.
>     * cp-tree.h: Declare it.
>     * decl.c (check_initializer): Use build_aggr_init for arrays
>     if it is false.
>     * init.c (build_vec_init): Avoid mixed signed/unsigned arithmetic.
> 
> Added:
>     branches/gcc-4_7-branch/gcc/testsuite/g++.dg/init/array34.C
> Modified:
>     branches/gcc-4_7-branch/gcc/cp/ChangeLog
>     branches/gcc-4_7-branch/gcc/cp/call.c
>     branches/gcc-4_7-branch/gcc/cp/cp-tree.h
>     branches/gcc-4_7-branch/gcc/cp/decl.c
>     branches/gcc-4_7-branch/gcc/cp/init.c


this patch breaks bootstrap:

../../gcc/cp/call.c: In function 'type_has_extended_temps':
../../gcc/cp/call.c:8852:7: error: 'for' loop initial declarations are only
allowed in C99 mode
../../gcc/cp/call.c:8852:7: note: use option -std=c99 or -std=gnu99 to compile
your code

[Bug c++/53650] [4.7 Regression] large array causes huge memory use

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-23 02:48:07 UTC ---
Author: jason
Date: Wed Jan 23 02:48:00 2013
New Revision: 195397

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=195397
Log:
    PR c++/53650
    * call.c (type_has_extended_temps): Fix C++ism.

Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/call.c