------- Comment #18 from tstarling at wikimedia dot org 2010-09-09 14:12 ------- Created an attachment (id=21752) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21752&action=view) gprof output
I haven't managed to get libstdc++ to compile with -pg, but compiling the test program with -static at least gives you a function breakdown. gprof output attached for 1 million lines, 500 bytes per line. To summarise: fgetc: 36.13% istream::getline: 18.01% ungetc: 16.70% _IO_sputbackc: 9.54% stdio_sync_filebuf::underflow: 5.66% stdio_sync_filebuf::uflow: 4.93% I should have spotted it from reading the code, it's not a loop of getc(), it's a loop of ungetc(getc()) && getc(). It really demonstrates how poorly suited the streambuf interface is to unbuffered input. The virtual functions called by istream::getline() don't give much flexibility. So I still have no other ideas apart from breaking the ABI. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45574
