[lldb] Detach the child process when stepping over a fork

Step over thread plans were claiming to explain the fork stop reasons,
which prevented the default fork logic (detaching from the child
process) from kicking in. This patch changes that.

Differential Revision: https://reviews.llvm.org/D141605

diff --git a/lldb/source/Target/ThreadPlan.cpp b/lldb/source/Target/ThreadPlan.cpp
index 9913ecb..7927fc3 100644 (file)
--- a/lldb/source/Target/ThreadPlan.cpp
+++ b/lldb/source/Target/ThreadPlan.cpp
@@ -171,6 +171,9 @@ bool ThreadPlan::IsUsuallyUnexplainedStopReason(lldb::StopReason reason) {
   case eStopReasonExec:
   case eStopReasonThreadExiting:
   case eStopReasonInstrumentation:
+  case eStopReasonFork:
+  case eStopReasonVFork:
+  case eStopReasonVForkDone:
     return true;
   default:
     return false;

diff --git a/lldb/test/API/functionalities/fork/resumes-child/Makefile b/lldb/test/API/functionalities/fork/resumes-child/Makefile
new file mode 100644 (file)
index 0000000..99998b2
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/resumes-child/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules

diff --git a/lldb/test/API/functionalities/fork/resumes-child/TestForkResumesChild.py b/lldb/test/API/functionalities/fork/resumes-child/TestForkResumesChild.py
new file mode 100644 (file)
index 0000000..70df4f1
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/resumes-child/TestForkResumesChild.py
@@ -0,0 +1,22 @@
+"""
+Make sure that the fork child keeps running.
+"""
+
+
+
+import lldb
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+
+
+class TestForkResumesChild(TestBase):
+
+    NO_DEBUG_INFO_TESTCASE = True
+
+    @skipIfWindows
+    def test_step_over_fork(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.cpp"))
+        self.runCmd("next")
+        self.expect("continue", substrs = ["exited with status = 0"])

diff --git a/lldb/test/API/functionalities/fork/resumes-child/main.cpp b/lldb/test/API/functionalities/fork/resumes-child/main.cpp
new file mode 100644 (file)
index 0000000..2d37f32
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/resumes-child/main.cpp
@@ -0,0 +1,29 @@
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
+#include <sys/wait.h>
+#include <thread>
+#include <unistd.h>
+
+int main() {
+  pid_t fork_result = fork(); // break here
+  assert(fork_result >= 0);
+  if (fork_result == 0) {
+    // child
+    _exit(47);
+  }
+  // parent
+  // Use polling to avoid blocking if the child is not actually resumed.
+  auto deadline = std::chrono::steady_clock::now() + std::chrono::seconds(10);
+  std::chrono::milliseconds poll_interval{10};
+  while (std::chrono::steady_clock::now() < deadline) {
+    int status;
+    pid_t waitpid_result = waitpid(fork_result, &status, WNOHANG);
+    if (waitpid_result == fork_result)
+      return 0;
+    assert(waitpid_result == 0);
+    std::this_thread::sleep_for(poll_interval);
+    poll_interval *= 2;
+  }
+  abort();
+}