Author: petr.pavlu Date: Wed Jul 12 05:38:31 2017 New Revision: 307782 URL: http://llvm.org/viewvc/llvm-project?rev=307782&view=rev Log: [MainLoop] Fix possible use of an invalid iterator
Store file descriptors from loop.m_read_fds (if FORCE_PSELECT is defined) and signals from loop.m_signals that need to be processed in MainLoop::RunImpl::ProcessEvents() into a separate vector and then iterate over this container to invoke the callbacks. This prevents a problem where when the code iterated directly over m_read_fds/m_signals, a callback invoked from within the loop could modify these variables and invalidate the loop iterator. This would then result in an assertion failure in llvm::DenseMapIterator::operator++(). Differential Revision: https://reviews.llvm.org/D35298 Modified: lldb/trunk/source/Host/common/MainLoop.cpp Modified: lldb/trunk/source/Host/common/MainLoop.cpp URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Host/common/MainLoop.cpp?rev=307782&r1=307781&r2=307782&view=diff ============================================================================== --- lldb/trunk/source/Host/common/MainLoop.cpp (original) +++ lldb/trunk/source/Host/common/MainLoop.cpp Wed Jul 12 05:38:31 2017 @@ -193,10 +193,16 @@ Status MainLoop::RunImpl::Poll() { void MainLoop::RunImpl::ProcessEvents() { #ifdef FORCE_PSELECT - for (const auto &fd : loop.m_read_fds) { - if (!FD_ISSET(fd.first, &read_fd_set)) - continue; - IOObject::WaitableHandle handle = fd.first; + // Collect first all readable file descriptors into a separate vector and then + // iterate over it to invoke callbacks. Iterating directly over + // loop.m_read_fds is not possible because the callbacks can modify the + // container which could invalidate the iterator. + std::vector<IOObject::WaitableHandle> fds; + for (const auto &fd : loop.m_read_fds) + if (FD_ISSET(fd.first, &read_fd_set)) + fds.push_back(fd.first); + + for (const auto &handle : fds) { #else for (const auto &fd : read_fds) { if ((fd.revents & POLLIN) == 0) @@ -209,13 +215,16 @@ void MainLoop::RunImpl::ProcessEvents() loop.ProcessReadObject(handle); } - for (const auto &entry : loop.m_signals) { + std::vector<int> signals; + for (const auto &entry : loop.m_signals) + if (g_signal_flags[entry.first] != 0) + signals.push_back(entry.first); + + for (const auto &signal : signals) { if (loop.m_terminate_request) return; - if (g_signal_flags[entry.first] == 0) - continue; // No signal - g_signal_flags[entry.first] = 0; - loop.ProcessSignal(entry.first); + g_signal_flags[signal] = 0; + loop.ProcessSignal(signal); } } #endif _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
