[Lldb-commits] [lldb] a3dc77c - [lldb] Support stepping through C++ thunks (#127419)
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lldb-commits at lists.llvm.org
Mon Feb 17 15:44:45 PST 2025
Author: Jonas Devlieghere
Date: 2025-02-17T15:44:41-08:00
New Revision: a3dc77c00a012bb613cb08e669dab4fadf88e935
URL: https://github.com/llvm/llvm-project/commit/a3dc77c00a012bb613cb08e669dab4fadf88e935
DIFF: https://github.com/llvm/llvm-project/commit/a3dc77c00a012bb613cb08e669dab4fadf88e935.diff
LOG: [lldb] Support stepping through C++ thunks (#127419)
This PR fixes LLDB stepping out, rather than stepping through a C++
thunk. The implementation is based on, and upstreams, the support for
runtime thunks in the Swift fork.
Fixes #43413
Added:
lldb/test/API/lang/cpp/thunk/Makefile
lldb/test/API/lang/cpp/thunk/TestThunk.py
lldb/test/API/lang/cpp/thunk/main.cpp
Modified:
lldb/include/lldb/Target/LanguageRuntime.h
lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
lldb/source/Target/ThreadPlanShouldStopHere.cpp
Removed:
################################################################################
diff --git a/lldb/include/lldb/Target/LanguageRuntime.h b/lldb/include/lldb/Target/LanguageRuntime.h
index f9ae2dc589632..7e4c11df0da7f 100644
--- a/lldb/include/lldb/Target/LanguageRuntime.h
+++ b/lldb/include/lldb/Target/LanguageRuntime.h
@@ -201,6 +201,8 @@ class LanguageRuntime : public Runtime, public PluginInterface {
return false;
}
+ virtual bool IsSymbolARuntimeThunk(const Symbol &symbol) { return false; }
+
// Given the name of a runtime symbol (e.g. in Objective-C, an ivar offset
// symbol), try to determine from the runtime what the value of that symbol
// would be. Useful when the underlying binary is stripped.
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
index 42fa54634841c..21a5ebe53073a 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
@@ -476,3 +476,14 @@ CPPLanguageRuntime::GetStepThroughTrampolinePlan(Thread &thread,
return ret_plan_sp;
}
+
+bool CPPLanguageRuntime::IsSymbolARuntimeThunk(const Symbol &symbol) {
+ llvm::StringRef mangled_name =
+ symbol.GetMangled().GetMangledName().GetStringRef();
+ // Virtual function overriding from a non-virtual base use a "Th" prefix.
+ // Virtual function overriding from a virtual base must use a "Tv" prefix.
+ // Virtual function overriding thunks with covariant returns use a "Tc"
+ // prefix.
+ return mangled_name.starts_with("_ZTh") || mangled_name.starts_with("_ZTv") ||
+ mangled_name.starts_with("_ZTc");
+}
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
index 57cfe28245808..05639e9798917 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
@@ -78,6 +78,9 @@ class CPPLanguageRuntime : public LanguageRuntime {
bool stop_others) override;
bool IsAllowedRuntimeValue(ConstString name) override;
+
+ bool IsSymbolARuntimeThunk(const Symbol &symbol) override;
+
protected:
// Classes that inherit from CPPLanguageRuntime can see and modify these
CPPLanguageRuntime(Process *process);
diff --git a/lldb/source/Target/ThreadPlanShouldStopHere.cpp b/lldb/source/Target/ThreadPlanShouldStopHere.cpp
index e72f8d8f51a20..fa6bc08a9914d 100644
--- a/lldb/source/Target/ThreadPlanShouldStopHere.cpp
+++ b/lldb/source/Target/ThreadPlanShouldStopHere.cpp
@@ -8,6 +8,7 @@
#include "lldb/Target/ThreadPlanShouldStopHere.h"
#include "lldb/Symbol/Symbol.h"
+#include "lldb/Target/LanguageRuntime.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/Thread.h"
#include "lldb/Utility/LLDBLog.h"
@@ -76,6 +77,19 @@ bool ThreadPlanShouldStopHere::DefaultShouldStopHereCallback(
}
}
+ // Check whether the frame we are in is a language runtime thunk, only for
+ // step out:
+ if (operation == eFrameCompareOlder) {
+ if (Symbol *symbol = frame->GetSymbolContext(eSymbolContextSymbol).symbol) {
+ ProcessSP process_sp(current_plan->GetThread().GetProcess());
+ for (auto *runtime : process_sp->GetLanguageRuntimes()) {
+ if (runtime->IsSymbolARuntimeThunk(*symbol)) {
+ should_stop_here = false;
+ break;
+ }
+ }
+ }
+ }
// Always avoid code with line number 0.
// FIXME: At present the ShouldStop and the StepFromHere calculate this
// independently. If this ever
@@ -109,18 +123,35 @@ ThreadPlanSP ThreadPlanShouldStopHere::DefaultStepFromHereCallback(
if (sc.line_entry.line == 0) {
AddressRange range = sc.line_entry.range;
-
- // If the whole function is marked line 0 just step out, that's easier &
- // faster than continuing to step through it.
bool just_step_out = false;
- if (sc.symbol && sc.symbol->ValueIsAddress()) {
- Address symbol_end = sc.symbol->GetAddress();
- symbol_end.Slide(sc.symbol->GetByteSize() - 1);
- if (range.ContainsFileAddress(sc.symbol->GetAddress()) &&
- range.ContainsFileAddress(symbol_end)) {
- LLDB_LOGF(log, "Stopped in a function with only line 0 lines, just "
- "stepping out.");
- just_step_out = true;
+ if (sc.symbol) {
+ ProcessSP process_sp(current_plan->GetThread().GetProcess());
+
+ // If this is a runtime thunk, step through it, rather than stepping out
+ // because it's marked line 0.
+ bool is_thunk = false;
+ for (auto *runtime : process_sp->GetLanguageRuntimes()) {
+ if (runtime->IsSymbolARuntimeThunk(*sc.symbol)) {
+ LLDB_LOGF(log, "In runtime thunk %s - stepping out.",
+ sc.symbol->GetName().GetCString());
+ is_thunk = true;
+ break;
+ }
+ }
+
+ // If the whole function is marked line 0 just step out, that's easier &
+ // faster than continuing to step through it.
+ // FIXME: This assumes that the function is a single line range. It could
+ // be a series of contiguous line 0 ranges. Check for that too.
+ if (!is_thunk && sc.symbol->ValueIsAddress()) {
+ Address symbol_end = sc.symbol->GetAddress();
+ symbol_end.Slide(sc.symbol->GetByteSize() - 1);
+ if (range.ContainsFileAddress(sc.symbol->GetAddress()) &&
+ range.ContainsFileAddress(symbol_end)) {
+ LLDB_LOGF(log, "Stopped in a function with only line 0 lines, just "
+ "stepping out.");
+ just_step_out = true;
+ }
}
}
if (!just_step_out) {
diff --git a/lldb/test/API/lang/cpp/thunk/Makefile b/lldb/test/API/lang/cpp/thunk/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/thunk/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/thunk/TestThunk.py b/lldb/test/API/lang/cpp/thunk/TestThunk.py
new file mode 100644
index 0000000000000..ceb16263648d6
--- /dev/null
+++ b/lldb/test/API/lang/cpp/thunk/TestThunk.py
@@ -0,0 +1,46 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class ThunkTest(TestBase):
+ def test_step_through_thunk(self):
+ self.build()
+ lldbutil.run_to_name_breakpoint(self, "testit")
+
+ # Make sure we step through the thunk into Derived1::doit
+ self.expect(
+ "step",
+ STEP_IN_SUCCEEDED,
+ substrs=["stop reason = step in", "Derived1::doit"],
+ )
+
+ self.runCmd("continue")
+
+ self.expect(
+ "step",
+ STEP_IN_SUCCEEDED,
+ substrs=["stop reason = step in", "Derived2::doit"],
+ )
+
+ def test_step_out_thunk(self):
+ self.build()
+ lldbutil.run_to_name_breakpoint(self, "testit_debug")
+
+ # Make sure we step out of the thunk and end up in testit_debug.
+ source = "main.cpp"
+ line = line_number(source, "// Step here")
+ self.expect(
+ "step",
+ STEP_IN_SUCCEEDED,
+ substrs=["stop reason = step in", "{}:{}".format(source, line)],
+ )
+
+ self.runCmd("continue")
+
+ self.expect(
+ "step",
+ STEP_IN_SUCCEEDED,
+ substrs=["stop reason = step in", "Derived2::doit_debug"],
+ )
diff --git a/lldb/test/API/lang/cpp/thunk/main.cpp b/lldb/test/API/lang/cpp/thunk/main.cpp
new file mode 100644
index 0000000000000..82d17b1350093
--- /dev/null
+++ b/lldb/test/API/lang/cpp/thunk/main.cpp
@@ -0,0 +1,48 @@
+#include <stdio.h>
+
+class Base1 {
+public:
+ virtual ~Base1() {}
+};
+
+class Base2 {
+public:
+ virtual void doit() = 0;
+ virtual void doit_debug() = 0;
+};
+
+Base2 *b;
+
+class Derived1 : public Base1, public Base2 {
+public:
+ virtual void doit() { printf("Derived1\n"); }
+ virtual void __attribute__((nodebug)) doit_debug() {
+ printf("Derived1 (no debug)\n");
+ }
+};
+
+class Derived2 : public Base2 {
+public:
+ virtual void doit() { printf("Derived2\n"); }
+ virtual void doit_debug() { printf("Derived2 (debug)\n"); }
+};
+
+void testit() { b->doit(); }
+
+void testit_debug() {
+ b->doit_debug();
+ printf("This is where I should step out to with nodebug.\n"); // Step here
+}
+
+int main() {
+
+ b = new Derived1();
+ testit();
+ testit_debug();
+
+ b = new Derived2();
+ testit();
+ testit_debug();
+
+ return 0;
+}
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