[Lldb-commits] [lldb] 38ecfd2 - [lldb] Add stop-on-fork and stop-on-vfork settings (#188710)
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Sat Jul 4 03:49:56 PDT 2026
Author: Sergei Druzhkov
Date: 2026-07-04T13:49:50+03:00
New Revision: 38ecfd2c0d9acef2ea328fb88550a3846ac5c9fe
URL: https://github.com/llvm/llvm-project/commit/38ecfd2c0d9acef2ea328fb88550a3846ac5c9fe
DIFF: https://github.com/llvm/llvm-project/commit/38ecfd2c0d9acef2ea328fb88550a3846ac5c9fe.diff
LOG: [lldb] Add stop-on-fork and stop-on-vfork settings (#188710)
Added support for new `target.process.stop-on-fork` and
`target.process.stop-on-vfork` settings. GDB already has ability to set
[catchpoints](https://www.sourceware.org/gdb/current/onlinedocs/gdb.html/Set-Catchpoints.html)
on `fork` and `vfork`, so having this feature in LLDB might be useful
(e.g. use it to get pid of new process and attach to the new process
from different console).
Added:
lldb/test/API/functionalities/fork/stop/Makefile
lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py
lldb/test/API/functionalities/fork/stop/main.c
lldb/test/Shell/Subprocess/stop-on-fork.test
lldb/test/Shell/Subprocess/stop-on-vfork.test
Modified:
lldb/include/lldb/Target/Process.h
lldb/source/Target/Process.cpp
lldb/source/Target/StopInfo.cpp
lldb/source/Target/TargetProperties.td
Removed:
################################################################################
diff --git a/lldb/include/lldb/Target/Process.h b/lldb/include/lldb/Target/Process.h
index 7b1424e6dfa59..80b3fa300971f 100644
--- a/lldb/include/lldb/Target/Process.h
+++ b/lldb/include/lldb/Target/Process.h
@@ -108,6 +108,8 @@ class ProcessProperties : public Properties {
bool GetWarningsOptimization() const;
bool GetWarningsUnsupportedLanguage() const;
bool GetStopOnExec() const;
+ bool GetStopOnFork() const;
+ bool GetStopOnVFork() const;
std::chrono::seconds GetUtilityExpressionTimeout() const;
std::chrono::seconds GetInterruptTimeout() const;
bool GetOSPluginReportsAllThreads() const;
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 4360250b21475..d929f45419783 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -343,6 +343,18 @@ bool ProcessProperties::GetUseDelayedBreakpoints() const {
idx, g_process_properties[idx].default_uint_value != 0);
}
+bool ProcessProperties::GetStopOnFork() const {
+ const uint32_t idx = ePropertyStopOnFork;
+ return GetPropertyAtIndexAs<bool>(
+ idx, g_process_properties[idx].default_uint_value != 0);
+}
+
+bool ProcessProperties::GetStopOnVFork() const {
+ const uint32_t idx = ePropertyStopOnVFork;
+ return GetPropertyAtIndexAs<bool>(
+ idx, g_process_properties[idx].default_uint_value != 0);
+}
+
std::chrono::seconds ProcessProperties::GetUtilityExpressionTimeout() const {
const uint32_t idx = ePropertyUtilityExpressionTimeout;
uint64_t value = GetPropertyAtIndexAs<uint64_t>(
diff --git a/lldb/source/Target/StopInfo.cpp b/lldb/source/Target/StopInfo.cpp
index c20b0ed07ee3c..80d7b3b4c2c01 100644
--- a/lldb/source/Target/StopInfo.cpp
+++ b/lldb/source/Target/StopInfo.cpp
@@ -1545,8 +1545,8 @@ class StopInfoFork : public StopInfo {
bool ShouldStop(Event *event_ptr) override {
// During expression evaluation, return true so that the fork event
// reaches RunThreadPlan as a real stop (not auto-restarted by
- // DoOnRemoval). RunThreadPlan decides whether to stop or continue
- // based on the stop-on-fork option.
+ // DoOnRemoval) or target.process.stop-on-fork is true. RunThreadPlan
+ // decides whether to stop or continue based on the stop-on-fork option.
//
// We check per-thread (not just process-wide IsRunningExpression)
// because other threads may fork concurrently after the
@@ -1554,8 +1554,9 @@ class StopInfoFork : public StopInfo {
ThreadSP thread_sp(m_thread_wp.lock());
if (thread_sp) {
ProcessSP process_sp = thread_sp->GetProcess();
- if (process_sp && process_sp->GetModIDRef().IsRunningExpression() &&
- thread_sp->IsRunningCallFunctionPlan())
+ if (process_sp && ((process_sp->GetModIDRef().IsRunningExpression() &&
+ thread_sp->IsRunningCallFunctionPlan()) ||
+ process_sp->GetStopOnFork()))
return true;
}
return false;
@@ -1610,8 +1611,9 @@ class StopInfoVFork : public StopInfo {
ThreadSP thread_sp(m_thread_wp.lock());
if (thread_sp) {
ProcessSP process_sp = thread_sp->GetProcess();
- if (process_sp && process_sp->GetModIDRef().IsRunningExpression() &&
- thread_sp->IsRunningCallFunctionPlan())
+ if (process_sp && ((process_sp->GetModIDRef().IsRunningExpression() &&
+ thread_sp->IsRunningCallFunctionPlan()) ||
+ process_sp->GetStopOnVFork()))
return true;
}
return false;
diff --git a/lldb/source/Target/TargetProperties.td b/lldb/source/Target/TargetProperties.td
index d63bc741e66ed..bf016b52afb83 100644
--- a/lldb/source/Target/TargetProperties.td
+++ b/lldb/source/Target/TargetProperties.td
@@ -282,6 +282,14 @@ let Definition = "process", Path = "target.process" in {
Global,
DefaultTrue,
Desc<"If true, stop when the inferior exec's.">;
+ def StopOnFork: Property<"stop-on-fork", "Boolean">,
+ Global,
+ DefaultFalse,
+ Desc<"If true, stop when the inferior forks. The stop location depends on target.process.follow-fork-mode: 'child' stops in the child process, while 'parent' stops in the original process.">;
+ def StopOnVFork: Property<"stop-on-vfork", "Boolean">,
+ Global,
+ DefaultFalse,
+ Desc<"If true, stop when the inferior vforks. The stop location depends on target.process.follow-fork-mode: 'child' stops in the child process, while 'parent' stops in the original process.">;
def UtilityExpressionTimeout: Property<"utility-expression-timeout", "UInt64">,
#ifdef LLDB_SANITIZED
DefaultUnsignedValue<60>,
diff --git a/lldb/test/API/functionalities/fork/stop/Makefile b/lldb/test/API/functionalities/fork/stop/Makefile
new file mode 100644
index 0000000000000..10495940055b6
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/stop/Makefile
@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules
diff --git a/lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py b/lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py
new file mode 100644
index 0000000000000..9fc85020e66f4
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py
@@ -0,0 +1,71 @@
+"""
+Make sure that we stop on fork and follow mode works.
+"""
+
+import lldb
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+
+
+class TestStopOnForkAndVFork(TestBase):
+ NO_DEBUG_INFO_TESTCASE = True
+
+ def do_test(self, mode, fork):
+ self.build()
+
+ args = [fork]
+ launch_info = lldb.SBLaunchInfo(args)
+ launch_info.SetWorkingDirectory(self.getBuildDir())
+
+ (_, process, _, _) = lldbutil.run_to_source_breakpoint(
+ self, "// break here", lldb.SBFileSpec("main.c"), launch_info
+ )
+ self.runCmd(f"settings set target.process.stop-on-{fork} true")
+ self.runCmd(f"settings set target.process.follow-fork-mode {mode}")
+
+ pid = process.GetProcessID()
+
+ process.Continue()
+ self.assertState(
+ process.GetState(),
+ lldb.eStateStopped,
+ f"Process should be stopped at {fork}",
+ )
+ threads = lldbutil.get_stopped_threads(
+ process, lldb.eStopReasonVFork if fork == "vfork" else lldb.eStopReasonFork
+ )
+ self.assertEqual(len(threads), 1, f"We got a thread stopped for {fork}.")
+
+ if mode == "parent":
+ self.assertEqual(
+ self.dbg.GetSelectedTarget().GetProcess().GetProcessID(), pid
+ )
+ self.expect(
+ "continue",
+ substrs=[f"exited with status = 0"],
+ )
+ else: # child
+ self.assertNotEqual(
+ self.dbg.GetSelectedTarget().GetProcess().GetProcessID(), pid
+ )
+ self.expect(
+ "continue",
+ substrs=[f"exited with status = 47"],
+ )
+
+ @skipIfWindows
+ def test_stop_on_fork_and_follow_parent(self):
+ self.do_test("parent", "fork")
+
+ @skipIfWindows
+ def test_stop_on_fork_and_follow_child(self):
+ self.do_test("child", "fork")
+
+ @skipIfWindows
+ def test_stop_on_vfork_and_follow_parent(self):
+ self.do_test("parent", "vfork")
+
+ @skipIfWindows
+ def test_stop_on_vfork_and_follow_child(self):
+ self.do_test("child", "vfork")
diff --git a/lldb/test/API/functionalities/fork/stop/main.c b/lldb/test/API/functionalities/fork/stop/main.c
new file mode 100644
index 0000000000000..3849e2fc24a6c
--- /dev/null
+++ b/lldb/test/API/functionalities/fork/stop/main.c
@@ -0,0 +1,18 @@
+#include <assert.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[]) {
+ if (argc != 2) {
+ _exit(1);
+ }
+ // break here
+ pid_t pid = strcmp(argv[1], "fork") == 0 ? fork() : vfork();
+ if (pid == 0) {
+ // child
+ _exit(47);
+ }
+ // parent
+ _exit(0);
+}
diff --git a/lldb/test/Shell/Subprocess/stop-on-fork.test b/lldb/test/Shell/Subprocess/stop-on-fork.test
new file mode 100644
index 0000000000000..a83dd613620d7
--- /dev/null
+++ b/lldb/test/Shell/Subprocess/stop-on-fork.test
@@ -0,0 +1,11 @@
+# REQUIRES: native
+# UNSUPPORTED: system-windows
+# RUN: %clangxx_host %p/Inputs/fork.cpp -DTEST_FORK=fork -o %t
+# RUN: %lldb -b -s %s %t | FileCheck %s
+settings set target.process.stop-on-fork true
+process launch
+# CHECK-NOT: function run in parent
+# CHECK: stop reason = fork
+continue
+# CHECK: function run in parent
+# CHECK: function run in exec'd child
diff --git a/lldb/test/Shell/Subprocess/stop-on-vfork.test b/lldb/test/Shell/Subprocess/stop-on-vfork.test
new file mode 100644
index 0000000000000..728858170273a
--- /dev/null
+++ b/lldb/test/Shell/Subprocess/stop-on-vfork.test
@@ -0,0 +1,11 @@
+# REQUIRES: native
+# UNSUPPORTED: system-windows
+# RUN: %clangxx_host %p/Inputs/fork.cpp -DTEST_FORK=vfork -o %t
+# RUN: %lldb -b -s %s %t | FileCheck %s
+settings set target.process.stop-on-vfork true
+process launch
+# CHECK-NOT: function run in parent
+# CHECK: stop reason = vfork
+continue
+# CHECK: function run in parent
+# CHECK: function run in exec'd child
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