https://github.com/DrSergei created https://github.com/llvm/llvm-project/pull/208165
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). >From 55088a780026ca177c4e831d773fc1a9955fbd71 Mon Sep 17 00:00:00 2001 From: Sergei Druzhkov <[email protected]> Date: Sat, 4 Jul 2026 13:49:50 +0300 Subject: [PATCH] [lldb] Reland 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). --- lldb/include/lldb/Target/Process.h | 2 + lldb/source/Target/Process.cpp | 12 ++++ lldb/source/Target/StopInfo.cpp | 14 ++-- lldb/source/Target/TargetProperties.td | 8 +++ .../API/functionalities/fork/stop/Makefile | 3 + .../fork/stop/TestStopOnForkAndVFork.py | 70 +++++++++++++++++++ .../test/API/functionalities/fork/stop/main.c | 18 +++++ lldb/test/Shell/Subprocess/stop-on-fork.test | 12 ++++ lldb/test/Shell/Subprocess/stop-on-vfork.test | 12 ++++ 9 files changed, 145 insertions(+), 6 deletions(-) create mode 100644 lldb/test/API/functionalities/fork/stop/Makefile create mode 100644 lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py create mode 100644 lldb/test/API/functionalities/fork/stop/main.c create mode 100644 lldb/test/Shell/Subprocess/stop-on-fork.test create mode 100644 lldb/test/Shell/Subprocess/stop-on-vfork.test 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..4d0c828f913f3 --- /dev/null +++ b/lldb/test/API/functionalities/fork/stop/TestStopOnForkAndVFork.py @@ -0,0 +1,70 @@ +""" +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 * + + +@skipIfWindows +@skipIfDarwin +@skipIfWasm # no fork() on WebAssembly +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.get_process_working_directory()) + + (_, 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"], + ) + + def test_stop_on_fork_and_follow_parent(self): + self.do_test("parent", "fork") + + def test_stop_on_fork_and_follow_child(self): + self.do_test("child", "fork") + + def test_stop_on_vfork_and_follow_parent(self): + self.do_test("parent", "vfork") + + 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..4c62928f001f5 --- /dev/null +++ b/lldb/test/Shell/Subprocess/stop-on-fork.test @@ -0,0 +1,12 @@ +# REQUIRES: native +# UNSUPPORTED: system-darwin +# 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..a9532e4641521 --- /dev/null +++ b/lldb/test/Shell/Subprocess/stop-on-vfork.test @@ -0,0 +1,12 @@ +# REQUIRES: native +# UNSUPPORTED: system-darwin +# 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 _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
