[Bug c++/50512] New: surprising change in overloading resolution

mm at mezzarobba dot net gcc-bugzilla@gcc.gnu.org
Sun Sep 25 16:51:00 GMT 2011 

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50512

             Bug #: 50512
           Summary: surprising change in overloading resolution
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mm@mezzarobba.net


The attached programm returns:

1 when compiled with g++ from the Debian package g++-4.6.1-9 (which says it is
based on SVN r178501);

2 with g++-4.6.1-10 (r178746) or g++-4.6.1-11;

1 again with g++-4.6.12 (r179140)

2 with gcc-snapshot-20110924-1 (trunk r179143).

I'm not 100% sure what the correct behaviour is, but the change does not look
deliberate. (Could it be related to PR c++/50442?)



~$ g++ -v test.cpp
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.1-12'
--with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6
--libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc
--with-arch-32=i586 --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 (Debian 4.6.1-12) 
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/cc1plus -quiet -v -imultilib . -imultiarch
x86_64-linux-gnu -D_GNU_SOURCE test.cpp -quiet -dumpbase test.cpp
-mtune=generic -march=x86-64 -auxbase test -version -o /tmp/ccHeTpTX.s
GNU C++ (Debian 4.6.1-12) version 4.6.1 (x86_64-linux-gnu)
        compiled by GNU C version 4.6.1, GMP version 5.0.2, MPFR version
3.0.1-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.6
 /usr/include/c++/4.6/x86_64-linux-gnu/.
 /usr/include/c++/4.6/backward
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++ (Debian 4.6.1-12) version 4.6.1 (x86_64-linux-gnu)
        compiled by GNU C version 4.6.1, GMP version 5.0.2, MPFR version
3.0.1-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: a48902e2296a3dd0e51e6adfff572b1c
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 as --64 -o /tmp/ccnazg5w.o /tmp/ccHeTpTX.s
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/4.6.1/collect2 --build-id --no-add-needed
--eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker
/lib64/ld-linux-x86-64.so.2
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu/crt1.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu/crti.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtbegin.o
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib -L/lib/x86_64-linux-gnu
-L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib
-L/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../.. /tmp/ccnazg5w.o -lstdc++ -lm
-lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/lib/gcc/x86_64-linux-gnu/4.6.1/crtend.o
/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../x86_64-linux-gnu/crtn.o
~$ ./a.out || echo $?
1



~$ g++ -v test.cpp
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 20110924-1'
--with-bugurl=file:///usr/share/doc/gcc-snapshot/README.Bugs
--enable-languages=c,ada,c++,java,fortran,objc,obj-c++,go
--prefix=/usr/lib/gcc-snapshot --enable-shared --enable-linker-build-id
--with-system-zlib --disable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.7-snap/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.7-snap
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.7-snap
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --with-arch-32=i586 --with-tune=generic --disable-werror
--enable-checking=yes --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.0 20110924 (experimental) [trunk revision 179143] (Debian
20110924-1) 
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/4.7.0/cc1plus -quiet -v
-imultilib . -imultiarch x86_64-linux-gnu -D_GNU_SOURCE test.cpp -quiet
-dumpbase test.cpp -mtune=generic -march=x86-64 -auxbase test -version -o
/tmp/cc3DRBsm.s
GNU C++ (Debian 20110924-1) version 4.7.0 20110924 (experimental) [trunk
revision 179143] (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0 20110924 (experimental) [trunk revision
179143], GMP version 5.0.2, MPFR version 3.0.1-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0

/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/x86_64-linux-gnu/.

/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/backward
 /usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/include
 /usr/local/include
 /usr/lib/gcc-snapshot/include
 /usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++ (Debian 20110924-1) version 4.7.0 20110924 (experimental) [trunk
revision 179143] (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0 20110924 (experimental) [trunk revision
179143], GMP version 5.0.2, MPFR version 3.0.1-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: a948ffbab3664787f27e8f65526c5e1e
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 as --64 -o /tmp/cc1MGhdw.o /tmp/cc3DRBsm.s
COMPILER_PATH=/usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/4.7.0/:/usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/4.7.0/:/usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/:/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/:/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/:/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/4.7.0/collect2 --build-id
--no-add-needed --eh-frame-hdr -m elf_x86_64 -dynamic-linker
/lib64/ld-linux-x86-64.so.2 /usr/lib/x86_64-linux-gnu/crt1.o
/usr/lib/x86_64-linux-gnu/crti.o
/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/crtbegin.o
-L/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0
-L/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib
-L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu
-L/usr/lib/../lib
-L/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/../../.. /tmp/cc1MGhdw.o
-lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/usr/lib/gcc-snapshot/lib/gcc/x86_64-linux-gnu/4.7.0/crtend.o
/usr/lib/x86_64-linux-gnu/crtn.o
~$ ./a.out || echo $?
2

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