I'm using fedora f12 x86_64. gcc-4.4.2-20.fc12.x86_64 gdb-7.0.1-29.fc12.x86_64 >From time to time, I need to use gdb. Today it's giving me a real hard time. Breakpoint 3, 0x000000000044f487 in ACMTx<boost::random::mersenne_twister<unsigned int, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18, 3346425566u> >::RandomTx() () (gdb) s Single stepping until exit from function _ZN5ACMTxIN5boost6random16mersenne_twisterIjLi32ELi624ELi397ELi31ELj2567483615ELi11ELi7ELj2636928640ELi15ELj4022730752ELi18ELj3346425566EEEE8RandomTxEv, which has no line number information. What's going on with the 'single stepping ..."? Everything was compiled with -g (and most or all without optimization). What could cause the 'no line number information'?