The attached short snippet fails to compile on GCC 4.4.1 and 4.4.2 (latest release), due to aliasing issues in stl::map. Ignore the logic as it has been contorted to reduce the test code fragment size.
First bug submit, so I hope this is close to proper procedure. ========================================================================== g++ -O2 -Wall -Werror -c tst5.cxx -*- mode: compilation; default-directory: "~/" -*- Compilation started at Tue Nov 17 21:37:41 g++ -v -save-temps -O2 -Wall -Werror -c tst5.cxx Using built-in specs. Target: x86_64-suse-linux Configured with: ../configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64 --enable-languages=c,c++,objc,fortran,obj-c++,java,ada --enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.4 --enable-ssp --disable-libssp --with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux' --disable-libgcj --disable-libmudflap --with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch --enable-version-specific-runtime-libs --program-suffix=-4.4 --enable-linux-futex --without-system-libunwind --with-arch-32=i586 --with-tune=generic --build=x86_64-suse-linux Thread model: posix gcc version 4.4.1 [gcc-4_4-branch revision 150839] (SUSE Linux) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O2' '-Wall' '-Werror' '-c' '-shared-libgcc' '-mtune=generic' /usr/lib64/gcc/x86_64-suse-linux/4.4/cc1plus -E -quiet -v -D_GNU_SOURCE tst5.cxx -mtune=generic -Wall -Werror -O2 -fpch-preprocess -o tst5.ii #include "..." search starts here: #include <...> search starts here: /usr/include/c++/4.4 /usr/include/c++/4.4/x86_64-suse-linux /usr/include/c++/4.4/backward /usr/local/include /usr/lib64/gcc/x86_64-suse-linux/4.4/include /usr/lib64/gcc/x86_64-suse-linux/4.4/include-fixed /usr/lib64/gcc/x86_64-suse-linux/4.4/../../../../x86_64-suse-linux/include /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O2' '-Wall' '-Werror' '-c' '-shared-libgcc' '-mtune=generic' /usr/lib64/gcc/x86_64-suse-linux/4.4/cc1plus -fpreprocessed tst5.ii -quiet -dumpbase tst5.cxx -mtune=generic -auxbase tst5 -O2 -Wall -Werror -version -o tst5.s GNU C++ (SUSE Linux) version 4.4.1 [gcc-4_4-branch revision 150839] (x86_64-suse-linux) compiled by GNU C version 4.4.1 [gcc-4_4-branch revision 150839], GMP version 4.3.1, MPFR version 2.4.1-p5. GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 9324fd3305365d6cc397a0043b4bc055 cc1plus: warnings being treated as errors tst5.cxx: In function 'int main()': tst5.cxx:23: error: dereferencing pointer '<anonymous>' does break strict-aliasing rules /usr/include/c++/4.4/bits/stl_tree.h:179: note: initialized from here Compilation exited abnormally with code 1 at Tue Nov 17 21:37:41 ========================================================================== SOURCE FOLLOWS: //============================================================================ // Compile with: g++ -O2 -Wall -Werror -c tst.cxx //============================================================================ #include <map> class C { typedef std::map< C *, C * > CloneList; static CloneList clone_list; public: C() {} C *clone() { clone_list.clear(); C *res = 0; CloneList::iterator ptr = clone_list.find( this ); if ( ptr != clone_list.end() ) res = ptr -> second; else { res = new C; clone_list[ this ] = res; } return res ; } } ; int main() { C *c = new C; return c -> clone() != 0; } //============================================================================ -- Summary: stl::map breaks strict-aliasing rules Product: gcc Version: 4.4.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: riddikulus at verizon dot net http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42087