[lldb][Format] Make function name frame-format variables work without debug-info (#137408)

This patch makes the frame-format variables introduced in
#131836 also work when no
debug-info is available. Previously, we assumed `sc.function` was
available, but without debug-info we might only have `sc.symbol`. We
don't really need the `sc.function` apart from when formatting
arguments.

For the function arguments case I added a fallback that will just print
the arguments we get from the demangler (which is what LLDB does for
stacktraces with no debug-info anyway). Ideally we'd have a separate
`FormatEntity::Entry::Type::FunctionArguments` that will just print the
arguments from the demangler and have something like the following in
the `plugin.cplusplus.display.function-name-format`:
```
{ ${function.formatted-arguments} || ${function.arguments} }
```
I.e., when we can't format the arguments, print the ones from the
demangler. But we currently don't have the `||` operator in the
frame-format language yet.

Author: Michael137

lldb/source/Core/FormatEntity.cpp

@@ -1809,11 +1809,12 @@ bool FormatEntity::Format(const Entry &entry, Stream &s,
   case Entry::Type::FunctionReturnRight:
   case Entry::Type::FunctionReturnLeft:
   case Entry::Type::FunctionQualifiers: {
-    if (!sc->function)
-      return false;
+    Language *language_plugin = nullptr;
+    if (sc->function)
+      language_plugin = Language::FindPlugin(sc->function->GetLanguage());
+    else if (sc->symbol)
+      language_plugin = Language::FindPlugin(sc->symbol->GetLanguage());
 
-    Language *language_plugin =
-        Language::FindPlugin(sc->function->GetLanguage());
     if (!language_plugin)
       return false;
 

lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

@@ -381,6 +381,34 @@ GetDemangledScope(const SymbolContext &sc) {
   return demangled_name.slice(info->ScopeRange.first, info->ScopeRange.second);
 }
 
+static bool PrintDemangledArgumentList(Stream &s, const SymbolContext &sc) {
+  assert(sc.symbol);
+
+  Mangled mangled = sc.GetPossiblyInlinedFunctionName();
+  if (!mangled)
+    return false;
+
+  auto demangled_name = mangled.GetDemangledName().GetStringRef();
+  if (demangled_name.empty())
+    return false;
+
+  const std::optional<DemangledNameInfo> &info = mangled.GetDemangledInfo();
+  if (!info)
+    return false;
+
+  // Function without a basename is nonsense.
+  if (!info->hasBasename())
+    return false;
+
+  if (info->ArgumentsRange.second < info->ArgumentsRange.first)
+    return false;
+
+  s << demangled_name.slice(info->ArgumentsRange.first,
+                            info->ArgumentsRange.second);
+
+  return true;
+}
+
 bool CPlusPlusLanguage::CxxMethodName::TrySimplifiedParse() {
   // This method tries to parse simple method definitions which are presumably
   // most comman in user programs. Definitions that can be parsed by this
@@ -1890,8 +1918,6 @@ bool CPlusPlusLanguage::GetFunctionDisplayName(
 bool CPlusPlusLanguage::HandleFrameFormatVariable(
     const SymbolContext &sc, const ExecutionContext *exe_ctx,
     FormatEntity::Entry::Type type, Stream &s) {
-  assert(sc.function);
-
   switch (type) {
   case FormatEntity::Entry::Type::FunctionScope: {
     std::optional<llvm::StringRef> scope = GetDemangledScope(sc);
@@ -1925,6 +1951,14 @@ bool CPlusPlusLanguage::HandleFrameFormatVariable(
   }
 
   case FormatEntity::Entry::Type::FunctionFormattedArguments: {
+    // This ensures we print the arguments even when no debug-info is available.
+    //
+    // FIXME: we should have a Entry::Type::FunctionArguments and
+    // use it in the plugin.cplusplus.display.function-name-format
+    // once we have a "fallback operator" in the frame-format language.
+    if (!sc.function && sc.symbol)
+      return PrintDemangledArgumentList(s, sc);
+
     VariableList args;
     if (auto variable_list_sp = GetFunctionVariableList(sc))
       variable_list_sp->AppendVariablesWithScope(eValueTypeVariableArgument,

lldb/test/Shell/Settings/TestFrameFormatFunctionBasename.test

@@ -7,6 +7,10 @@
 # RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
 #
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
+# RUN:       | FileCheck %s
+
 #--- main.cpp
 namespace ns {
 template<typename T>

lldb/test/Shell/Settings/TestFrameFormatFunctionFormattedArguments.test

@@ -6,6 +6,10 @@
 # RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.out
 # RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
+#
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
+# RUN:       | FileCheck %s --check-prefix=CHECK-NODEBUG
 
 #--- main.cpp
 struct Foo {
@@ -42,3 +46,8 @@ bt
 # CHECK: custom-frame '({{.*}}=5, x=10)'
 # CHECK: custom-frame '(str="hello", fptr=({{.*}}.out`{{.*}}foo(int,{{.*}}int) at main.cpp:{{[0-9]+}}))'
 # CHECK: custom-frame '(argc=1, argv={{.*}})'
+
+# CHECK-NODEBUG: custom-frame '()'
+# CHECK-NODEBUG: custom-frame '()'
+# CHECK-NODEBUG: custom-frame '(int, int)'
+# CHECK-NODEBUG: custom-frame '(char const*, void (*)(int, int))'

lldb/test/Shell/Settings/TestFrameFormatFunctionQualifiers.test

@@ -6,6 +6,10 @@
 # RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.out
 # RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
+#
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
+# RUN:       | FileCheck %s
 
 #--- main.cpp
 struct Foo {

lldb/test/Shell/Settings/TestFrameFormatFunctionReturn.test

@@ -7,6 +7,10 @@
 # RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.out
 # RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
+#
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
+# RUN:       | FileCheck %s
 
 #--- main.cpp
 namespace ns::ns2 {

lldb/test/Shell/Settings/TestFrameFormatFunctionScope.test

@@ -4,8 +4,11 @@
 
 # RUN: split-file %s %t
 # RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.out
-# RUN: %lldb -o "settings set interpreter.stop-command-source-on-error false" \
-# RUN:       -x -b -s %t/commands.input %t.out -o exit 2>&1 \
+# RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
+# RUN:       | FileCheck %s
+#
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
 
 #--- main.cpp

lldb/test/Shell/Settings/TestFrameFormatFunctionTemplateArguments.test

@@ -3,8 +3,12 @@
 # Test the ${function.template-arguments} frame-format variable.
 
 # RUN: split-file %s %t
-# RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.cxx.out
-# RUN: %lldb -x -b -s %t/commands.input %t.cxx.out -o exit 2>&1 \
+# RUN: %clang_host -g -gdwarf %t/main.cpp -o %t.out
+# RUN: %lldb -x -b -s %t/commands.input %t.out -o exit 2>&1 \
+# RUN:       | FileCheck %s
+#
+# RUN: %clang_host -O0 %t/main.cpp -o %t-nodebug.out
+# RUN: %lldb -x -b -s %t/commands.input %t-nodebug.out -o exit 2>&1 \
 # RUN:       | FileCheck %s
 
 #--- main.cpp