[lldb] Fix ^C handling in IOHandlerProcessSTDIO

[labath]

Summary

D120762 accidentally moved the interrupt check into the block which was
reading stdio. This meant that a ^C only took effect after a regular
character has been pressed.

This patch fixes that and adds a (pexpect) test.

[DavidSpickett]

I also found this in the process of looking at https://github.com/llvm/llvm-project/issues/53673 (different issue same area).

Bisected it to the same change you got, and this fixes things for me too.

Do you know if the pexpect test will cleanup the debugee process if some part of the test fails? Or will we have that hanging around in its infinite loop?

[JDevlieghere]

Thanks!

[labath]

In D121912#3389378, @DavidSpickett wrote:

Do you know if the pexpect test will cleanup the debugee process if some part of the test fails? Or will we have that hanging around in its infinite loop?

It won't, but the debuggee is not doing an infinite loop. The while (std::getline(std::cin, str)) thingy will terminate when it reaches EOF, which will happen when lldb gets killed at the latest (if lldb is still somewhat functioning, it will kill the inferior first, when *it* detects the EOF).

lldb/lldb/test/API/iohandler/sigint/Makefile

+include Makefile.rules

lldb/lldb/test/API/iohandler/sigint/TestProcessIOHandlerInterrupt.py

+"""
+Test sending SIGINT Process IOHandler
+"""
+
+import os
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+class TestCase(PExpectTest):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test(self):
+        self.build(dictionary={"CXX_SOURCES":"cat.cpp"})
+        self.launch(executable=self.getBuildArtifact(), timeout=5)
+
+        self.child.sendline("process launch")
+        self.child.expect("Process .* launched")
+
+        self.child.sendline("Hello cat")
+        self.child.expect_exact("read: Hello cat")
+
+        self.child.sendintr()
+        self.child.expect("Process .* stopped")
+        self.expect_prompt()
+
+        self.expect("bt", substrs=["input_copy_loop"])
+
+        self.child.sendline("continue")
+        self.child.expect("Process .* resuming")
+
+        self.child.sendline("Goodbye cat")
+        self.child.expect_exact("read: Goodbye cat")
+
+        self.child.sendeof()
+        self.child.expect("Process .* exited")
+        self.expect_prompt()
+
+        self.quit()

lldb/lldb/test/API/iohandler/sigint/cat.cpp

+#include <iostream>
+
+void input_copy_loop() {
+  std::string str;
+  while (std::getline(std::cin, str))
+    std::cout << "read: " << str << std::endl;
+}
+
+int main() {
+  input_copy_loop();
+  return 0;
+}