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

david at doublewise dot net gcc-bugzilla@gcc.gnu.org
Tue Jun 12 23:38:00 GMT 2012


             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 {
    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.
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
--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
Thread model: posix
gcc version 4.7.0 20120507 (Red Hat 4.7.0-5) (GCC)

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