From 0877dd14e4e85550f8e267b5ceeff1d3409c41ba Mon Sep 17 00:00:00 2001 From: Vedant Kumar Date: Thu, 24 Oct 2019 13:15:37 -0700 Subject: [PATCH] [Driver] Force llvm to install its handlers before lldb's Install llvm's signal handlers up front to prevent lldb's handlers from being ignored. This is (hopefully) a stopgap workaround. When lldb invokes an llvm API that installs signal handlers (e.g. llvm::sys::RemoveFileOnSignal, possibly via a compiler embedded within lldb), lldb's signal handlers are overriden if llvm is installing its handlers for the first time. To work around llvm's behavior, force it to install its handlers up front, and *then* install lldb's handlers. In practice this is used to prevent lldb test processes from exiting due to IO_ERR when SIGPIPE is received. Note that when llvm installs its handlers, it 1) records the old handlers it replaces and 2) re-installs the old handlers when its new handler is invoked. That means that a signal not explicitly handled by lldb can fall back to being handled by llvm's handler the first time it is received, and then by the default handler the second time it is received. Differential Revision: https://reviews.llvm.org/D69403 --- lldb/tools/driver/Driver.cpp | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/lldb/tools/driver/Driver.cpp b/lldb/tools/driver/Driver.cpp index 4a403a7ffb4602..8140e2a04c6ec9 100644 --- a/lldb/tools/driver/Driver.cpp +++ b/lldb/tools/driver/Driver.cpp @@ -845,6 +845,25 @@ int main(int argc, char const *argv[]) } SBHostOS::ThreadCreated(""); + // Install llvm's signal handlers up front to prevent lldb's handlers from + // being ignored. This is (hopefully) a stopgap workaround. + // + // When lldb invokes an llvm API that installs signal handlers (e.g. + // llvm::sys::RemoveFileOnSignal, possibly via a compiler embedded within + // lldb), lldb's signal handlers are overriden if llvm is installing its + // handlers for the first time. + // + // To work around llvm's behavior, force it to install its handlers up front, + // and *then* install lldb's handlers. In practice this is used to prevent + // lldb test processes from exiting due to IO_ERR when SIGPIPE is received. + // + // Note that when llvm installs its handlers, it 1) records the old handlers + // it replaces and 2) re-installs the old handlers when its new handler is + // invoked. That means that a signal not explicitly handled by lldb can fall + // back to being handled by llvm's handler the first time it is received, + // and then by the default handler the second time it is received. + llvm::sys::AddSignalHandler([](void *) -> void {}, nullptr); + signal(SIGINT, sigint_handler); #if !defined(_MSC_VER) signal(SIGPIPE, SIG_IGN);