Just curious if anyone else has seen this or anything like it? Platform is Mac OS X 10.6.1, gcc 4.2.1, boost 1.40.0 installed from MacPorts, compiling 64-bit (default). Here's my test code: #include <sstream> int main() { std::ostringstream str; str << "Help Me!"; return 0; } Here's what I'm doing: % g++ -o streamtest_bad -ggdb -L/opt/local/lib -lboost_unit_test_framework-mt-d streamtest.cpp % ./streamtest_bad streamtest_bad(63554) malloc: *** error for object 0x7fff7008a500: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug zsh: abort ./streamtest_bad % Works fine against other boost libraries, eg system: % g++ -o streamtest_good -ggdb -L/opt/local/lib -lboost_system-mt-d streamtest.cpp % ./streamtest_good % Note that this seems to be a separate problem to that reported in ticket 3432 (https://svn.boost.org/trac/boost/ticket/3432). At least, I have verified that the framework::clear() function isn't being called in the above code, which does tend to point the finger at a different part of the library. The backtrace is not particularly enlightening, but posted here for the sake of completeness: (gdb) bt #0 0x00007fff87f92ff6 in __kill () #1 0x00007fff88034072 in abort () #2 0x00007fff87f4b095 in free () #3 0x0000000100005533 in __gnu_cxx::new_allocator<char>::deallocate (this=0x7fff5fbff5df, __p=0x7fff7008a500 "") at new_allocator.h:97 #4 0x0000000100005578 in std::string::_Rep::_M_destroy (this=0x7fff7008a500, __a=@0x7fff5fbff63f) at basic_string.tcc:431 #5 0x0000000100005939 in std::string::_Rep::_M_dispose (this=0x7fff7008a500, __a=@0x7fff5fbff63f) at basic_string.h:238 #6 0x000000010000596a in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string (this=0x7fff5fbff670) at basic_string.h:493 #7 0x000000010002ad55 in std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::overflow (this=0x7fff5fbff7f8, __c=72) at sstream.tcc:125 #8 0x0000000100029db0 in std::basic_streambuf<char, std::char_traits<char> >::xsputn (this=0x7fff5fbff7f8, __s=0x100000e7e "Help Me!", __n=8) at streambuf.tcc:102 #9 0x00007fff806e0ae4 in std::__ostream_write<char, std::char_traits<char> > () #10 0x00007fff806deb98 in std::__ostream_insert<char, std::char_traits<char> > () #11 0x00007fff806dec58 in std::operator<< <std::char_traits<char> > () #12 0x0000000100000d6b in main () at streamtest.cpp:6