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

llvm-svn: 375288

1 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Support/Unix/Signals.inc b/llvm/lib/Support/Unix/Signals.inc
index be05eabfb2e..5e0cde4a81e 100644
--- a/llvm/lib/Support/Unix/Signals.inc
+++ b/llvm/lib/Support/Unix/Signals.inc
@@ -82,12 +82,18 @@ using namespace llvm;
 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 @@ static RETSIGTYPE SignalHandler(int Sig) {
 
       // 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 @@ void llvm::sys::SetInfoSignalFunction(void (*Handler)()) {
   RegisterHandlers();
 }
 
+void llvm::sys::SetPipeSignalFunction(void (*Handler)()) {
+  PipeSignalFunction.exchange(Handler);
+  RegisterHandlers();
+}
+
 // The public API
 bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
                                    std::string* ErrMsg) {