The bug is present in the 4.2.0 release and still in the 20070523 snapshot. It was not present in 4.2-20070405-1 (from Debian experimental).
The error occured in a program using stxxl (http://stxxl.sourceforge.net) with mcstl (http://algo2.iti.uni-karlsruhe.de/singler/mcstl/). Since mcstl requires openmp, this can't be tested with g++ earlier than 4.2, although the problem does not look openmp related and it should be possible to produce a test case without mcstl/openmp dependency. I minimized the testcase to the following: #include <sstream> void f () { std::ostringstream str_; str_ << "x"; throw std::ios_base::failure(str_.str()); } and compiled it with /data/gcc/snapshot-4.2/bin/g++ -W -Wall -I /home/andreas/work/mpi/mcstl/c++ -I /home/andreas/work/mpi/mcstl/originals/_data_gcc_snapshot-4.2_include_c++_4.2.1 -c -O[23] t.cpp (.../mcstl/originals/_data_gcc_snapshot-4.2_include_c++_4.2.1/original is a symlink to /data/gcc/snapshot-4.2/include/c++/4.2.1 and required by mcstl to find the original STL headers, since mcstl wraps the STL headers in order to provide parallelism) Compiling with -O2 succeeds, while -O3 fails with /data/gcc/snapshot-4.2/lib/gcc/i686-pc-linux-gnu/4.2.1/../../../../include/c++/4.2.1/bits/ostream_insert.h: In function void std::__ostream_fill(std::basic_ostream<_CharT, _Traits>&, std::streamsize) [with _CharT = char, _Traits = std::char_traits<char>]: /data/gcc/snapshot-4.2/lib/gcc/i686-pc-linux-gnu/4.2.1/../../../../include/c++/4.2.1/bits/ostream_insert.h:96: instantiated from std::basic_ostream<_CharT, _Traits>& std::__ostream_insert(std::basic_ostream<_CharT, _Traits>&, const _CharT*, std::streamsize) [with _CharT = char, _Traits = std::char_traits<char>] /home/andreas/work/mpi/mcstl/originals/_data_gcc_snapshot-4.2_include_c++_4.2.1/original/ostream:517: instantiated from std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*) [with _Traits = std::char_traits<char>] t.cpp:7: instantiated from here /data/gcc/snapshot-4.2/lib/gcc/i686-pc-linux-gnu/4.2.1/../../../../include/c++/4.2.1/bits/ostream_insert.h:64: error: struct std::basic_ostream<char, std::char_traits<char> > has no member named fill -- Summary: g++ -O3 fails on code that compiles with -O2 Product: gcc Version: 4.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: regression AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: gcc at abeckmann dot de GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32072
