[Bug c++/55402] New: Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 Bug #: 55402 Summary: Compiling large initializer lists never finishes Classification: Unclassified Product: gcc Version: 4.7.2 Status: UNCONFIRMED Severity: major Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: ke...@topsy.com An initializer list of tens of thousands of simple std::pair<...> causes GCC 4.7.2 to busily never return. Command line: kevin@ps027:~$ cat /proc/version Linux version 2.6.32-32-server (buildd@allspice) (gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) ) #62-Ubuntu SMP Wed Apr 20 22:07:43 UTC 2011 kevin@ps027:~$ g++-4.7 --version g++-4.7 (Ubuntu/Linaro 4.7.2-2+ub1) 4.7.2 Copyright (C) 2012 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. kevin@ps027:~$ g++ -std=c++0x -save-temps hang.cc (never returns, compiler forever busy)
[Bug c++/55402] Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 --- Comment #1 from Kevin Hsu 2012-11-19 22:27:00 UTC --- In the example, the initializer list has maybe around 60,000 elements. This is pretty large, but by no means a corner case.
[Bug c++/55402] Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 --- Comment #2 from Kevin Hsu 2012-11-19 22:28:53 UTC --- Created attachment 28737 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28737 The .cc file, gzip'd In case it helps (gzipped)
[Bug c++/55402] Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 --- Comment #3 from Kevin Hsu 2012-11-19 22:30:48 UTC --- Created attachment 28738 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28738 intermediate file, gzipped
[Bug c++/55402] Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 --- Comment #4 from Kevin Hsu 2012-11-19 22:32:35 UTC --- (In reply to comment #0) > An initializer list of tens of thousands of simple std::pair<...> causes GCC > 4.7.2 to busily never return. > > Command line: > > kevin@ps027:~$ cat /proc/version > Linux version 2.6.32-32-server (buildd@allspice) (gcc version 4.4.3 (Ubuntu > 4.4.3-4ubuntu5) ) #62-Ubuntu SMP Wed Apr 20 22:07:43 UTC 2011 > kevin@ps027:~$ g++-4.7 --version > g++-4.7 (Ubuntu/Linaro 4.7.2-2+ub1) 4.7.2 > Copyright (C) 2012 Free Software Foundation, Inc. > This is free software; see the source for copying conditions. There is NO > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. > > kevin@ps027:~$ g++ -std=c++0x -save-temps hang.cc > (never returns, compiler forever busy) Oops, the actual command line used was indeed g++-4.7: kevin@ps027:~$ g++-4.7 -std=c++0x -save-temps hang.cc
[Bug c++/55402] Compiling large initializer lists never finishes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55402 --- Comment #6 from Kevin Hsu 2012-11-20 00:24:11 UTC --- (In reply to comment #5) > I don't think it's correct to say that it *never* finishes - the memory usage > also doesn't diverge - it's just extremely slow. We have of course to analyze > why (as far as I know nobody tested so far this typical ;) case). Right, I did test with a few thousand entries, and it did come back. It feels like there's a exponential issue somewhere... Anyways, thank you for looking into this :) The use case we encountered was that we have a global data structure with around 25,000 pairs known at compile time. So, we naturally generated the code file. I haven't tested whether this happens at all with std::unordered_map or other containers. My workaround was to change the ctor to take a pointer to the entries with a count. In that case, the C-style initialization compiles in expected time.
