Disable exit-on-SIGPIPE in lldb
Occasionally, during test teardown, LLDB writes to a closed pipe.
Sometimes the communication is inherently unreliable, so LLDB tries to
avoid being killed due to SIGPIPE (it calls `signal(SIGPIPE, SIG_IGN)`).
However, LLVM's default SIGPIPE behavior overrides LLDB's, causing it to
exit with IO_ERR.
Opt LLDB out of the default SIGPIPE behavior. I expect that this will
resolve some LLDB test suite flakiness (tests randomly failing with
IO_ERR) that we've seen since r344372.
rdar://55750240
Differential Revision: https://reviews.llvm.org/D69148
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375288 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/Support/Signals.h b/include/llvm/Support/Signals.h
index a6b215a..a4f1fad 100644
--- a/include/llvm/Support/Signals.h
+++ b/include/llvm/Support/Signals.h
@@ -84,6 +84,17 @@
/// function. Note also that the handler may be executed on a different
/// thread on some platforms.
void SetInfoSignalFunction(void (*Handler)());
+
+ /// Registers a function to be called when a "pipe" signal is delivered to
+ /// the process.
+ ///
+ /// The "pipe" signal typically indicates a failed write to a pipe (SIGPIPE).
+ /// The default installed handler calls `exit(EX_IOERR)`, causing the process
+ /// to immediately exit with an IO error exit code.
+ ///
+ /// This function is only applicable on POSIX systems.
+ void SetPipeSignalFunction(void (*Handler)());
+
} // End sys namespace
} // End llvm namespace
diff --git a/lib/Support/Unix/Signals.inc b/lib/Support/Unix/Signals.inc
index be05eab..5e0cde4 100644
--- a/lib/Support/Unix/Signals.inc
+++ b/lib/Support/Unix/Signals.inc
@@ -82,12 +82,18 @@
static RETSIGTYPE SignalHandler(int Sig); // defined below.
static RETSIGTYPE InfoSignalHandler(int Sig); // defined below.
+static void DefaultPipeSignalFunction() {
+ exit(EX_IOERR);
+}
+
using SignalHandlerFunctionType = void (*)();
/// The function to call if ctrl-c is pressed.
static std::atomic<SignalHandlerFunctionType> InterruptFunction =
ATOMIC_VAR_INIT(nullptr);
static std::atomic<SignalHandlerFunctionType> InfoSignalFunction =
ATOMIC_VAR_INIT(nullptr);
+static std::atomic<SignalHandlerFunctionType> PipeSignalFunction =
+ ATOMIC_VAR_INIT(DefaultPipeSignalFunction);
namespace {
/// Signal-safe removal of files.
@@ -363,7 +369,8 @@
// Send a special return code that drivers can check for, from sysexits.h.
if (Sig == SIGPIPE)
- exit(EX_IOERR);
+ if (SignalHandlerFunctionType CurrentPipeFunction = PipeSignalFunction)
+ CurrentPipeFunction();
raise(Sig); // Execute the default handler.
return;
@@ -403,6 +410,11 @@
RegisterHandlers();
}
+void llvm::sys::SetPipeSignalFunction(void (*Handler)()) {
+ PipeSignalFunction.exchange(Handler);
+ RegisterHandlers();
+}
+
// The public API
bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
std::string* ErrMsg) {
diff --git a/lib/Support/Windows/Signals.inc b/lib/Support/Windows/Signals.inc
index 6a820ef..d962daf 100644
--- a/lib/Support/Windows/Signals.inc
+++ b/lib/Support/Windows/Signals.inc
@@ -560,6 +560,9 @@
// Unimplemented.
}
+void llvm::sys::SetPipeSignalFunction(void (*Handler)()) {
+ // Unimplemented.
+}
/// Add a function to be called when a signal is delivered to the process. The
/// handler can have a cookie passed to it to identify what instance of the
diff --git a/unittests/Support/CMakeLists.txt b/unittests/Support/CMakeLists.txt
index 1618915..3851422 100644
--- a/unittests/Support/CMakeLists.txt
+++ b/unittests/Support/CMakeLists.txt
@@ -58,6 +58,7 @@
ReverseIterationTest.cpp
ReplaceFileTest.cpp
ScaledNumberTest.cpp
+ SignalsTest.cpp
SourceMgrTest.cpp
SpecialCaseListTest.cpp
StringPool.cpp
diff --git a/unittests/Support/SignalsTest.cpp b/unittests/Support/SignalsTest.cpp
new file mode 100644
index 0000000..6dfa4bf
--- /dev/null
+++ b/unittests/Support/SignalsTest.cpp
@@ -0,0 +1,53 @@
+//========- unittests/Support/SignalsTest.cpp - Signal handling test =========//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#if !defined(_WIN32)
+#include <unistd.h>
+#include <sysexits.h>
+#endif // !defined(_WIN32)
+
+#include "llvm/Support/Signals.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+#if !defined(_WIN32)
+TEST(SignalTest, IgnoreMultipleSIGPIPEs) {
+ // Ignore SIGPIPE.
+ signal(SIGPIPE, SIG_IGN);
+
+ // Disable exit-on-SIGPIPE.
+ sys::SetPipeSignalFunction(nullptr);
+
+ // Create unidirectional read/write pipes.
+ int fds[2];
+ int err = pipe(fds);
+ if (err != 0)
+ return; // If we can't make pipes, this isn't testing anything.
+
+ // Close the read pipe.
+ close(fds[0]);
+
+ // Attempt to write to the write pipe. Currently we're asserting that the
+ // write fails, which isn't great.
+ //
+ // What we really want is a death test that checks that this block exits
+ // with a special exit "success" code, as opposed to unexpectedly exiting due
+ // to a kill-by-SIGNAL or due to the default SIGPIPE handler.
+ //
+ // Unfortunately llvm's unit tests aren't set up to support death tests well.
+ // For one, death tests are flaky in a multithreaded context. And sigactions
+ // inherited from llvm-lit interfere with what's being tested.
+ const void *buf = (const void *)&fds;
+ err = write(fds[1], buf, 1);
+ ASSERT_EQ(err, -1);
+ err = write(fds[1], buf, 1);
+ ASSERT_EQ(err, -1);
+}
+#endif // !defined(_WIN32)
