[Signal] Allow llvm clients to opt into one-shot SIGPIPE handling

Allow clients of the llvm library to opt-in to one-shot SIGPIPE
handling, instead of forcing them to undo llvm's SIGPIPE handler
registration (which is brittle).

The current behavior is preserved for all llvm-derived tools (except
lldb) by means of a default-`true` flag in the InitLLVM constructor.

This prevents "IO error" crashes in long-lived processes (lldb is the
motivating example) which both a) load llvm as a dynamic library and b)
*really* need to ignore SIGPIPE.

As llvm signal handlers can be installed when calling into libclang
(say, via RemoveFileOnSignal), thereby overriding a previous SIG_IGN for
SIGPIPE, there is no clean way to opt-out of "exit-on-SIGPIPE" in the
current model.

Differential Revision: https://reviews.llvm.org/D70277

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Support/Windows/Signals.inc b/llvm/lib/Support/Windows/Signals.inc
index 6a820ef22b1..08a3616427b 100644
--- a/llvm/lib/Support/Windows/Signals.inc
+++ b/llvm/lib/Support/Windows/Signals.inc
@@ -560,6 +560,13 @@ void llvm::sys::SetInfoSignalFunction(void (*Handler)()) {
   // Unimplemented.
 }
 
+void llvm::sys::SetOneShotPipeSignalFunction(void (*Handler)()) {
+  // Unimplemented.
+}
+
+void llvm::sys::DefaultOneShotPipeSignalHandler() {
+  // 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