[lldb] Clear cached unwind plans when adding symbols (#125839)

PR #86603 broke unwinding in for unwind info added via "target symbols
add". #86770 attempted to fix this, but the fix was only partial -- it
accepted new sources of unwind information, but didn't take into account
that the symbol file can alter what lldb percieves as function
boundaries.

A stripped file will not contain information about private
(non-exported) symbols, which will make the public symbols appear very
large. If lldb tries to unwind from such a function before symbols are
added, then the cached unwind plan will prevent new (correct) unwind
plans from being created.

target-symbols-add-unwind.test might have caught this, were it not for
the fact that the "image show-unwind" command does *not* use cached
unwind information (it recomputes it from scratch).

The changes in this patch come in three pieces:
- Clear cached unwind plans when adding symbols. Since the symbol
boundaries can change, we cannot trust anything we've computed
previously.
- Add a flag to "image show-unwind" to display the cached unwind
information (mainly for the use in the test, but I think it's also
generally useful).
- Rewrite the test to better and more reliably simulate the real-world
scenario: I've swapped the running process for a core (minidump) file so
it can run anywhere; used the caching version of the show-unwind
command; and swapped C for assembly to better control the placement of
symbols

3 files changed, 23 insertions, 4 deletions

diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index d0092c2..da50fe0 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -3474,6 +3474,17 @@ public:
         m_type = eLookupTypeFunctionOrSymbol;
         break;
 
+      case 'c':
+        bool value, success;
+        value = OptionArgParser::ToBoolean(option_arg, false, &success);
+        if (success) {
+          m_cached = value;
+        } else {
+          return Status::FromErrorStringWithFormatv(
+              "invalid boolean value '%s' passed for -c option", option_arg);
+        }
+        break;
+
       default:
         llvm_unreachable("Unimplemented option");
       }
@@ -3485,6 +3496,7 @@ public:
       m_type = eLookupTypeInvalid;
       m_str.clear();
       m_addr = LLDB_INVALID_ADDRESS;
+      m_cached = false;
     }
 
     llvm::ArrayRef<OptionDefinition> GetDefinitions() override {
@@ -3497,6 +3509,7 @@ public:
                                      // parsing options
     std::string m_str; // Holds name lookup
     lldb::addr_t m_addr = LLDB_INVALID_ADDRESS; // Holds the address to lookup
+    bool m_cached = true;
   };
 
   CommandObjectTargetModulesShowUnwind(CommandInterpreter &interpreter)
@@ -3583,9 +3596,12 @@ protected:
       if (abi)
         start_addr = abi->FixCodeAddress(start_addr);
 
-      FuncUnwindersSP func_unwinders_sp(
-          sc.module_sp->GetUnwindTable()
-              .GetUncachedFuncUnwindersContainingAddress(start_addr, sc));
+      UnwindTable &uw_table = sc.module_sp->GetUnwindTable();
+      FuncUnwindersSP func_unwinders_sp =
+          m_options.m_cached
+              ? uw_table.GetFuncUnwindersContainingAddress(start_addr, sc)
+              : uw_table.GetUncachedFuncUnwindersContainingAddress(start_addr,
+                                                                   sc);
       if (!func_unwinders_sp)
         continue;
 
diff --git a/lldb/source/Commands/Options.td b/lldb/source/Commands/Options.td
index 777f8c3..8831fed 100644
--- a/lldb/source/Commands/Options.td
+++ b/lldb/source/Commands/Options.td
@@ -965,6 +965,8 @@ let Command = "target modules show unwind" in {
   def target_modules_show_unwind_address : Option<"address", "a">, Group<2>,
     Arg<"AddressOrExpression">, Desc<"Show unwind instructions for a function "
     "or symbol containing an address">;
+  def target_modules_show_unwind_cached : Option<"cached", "c">,
+    Arg<"Boolean">, Desc<"Show cached unwind information">;
 }
 
 let Command = "target modules lookup" in {
diff --git a/lldb/source/Symbol/UnwindTable.cpp b/lldb/source/Symbol/UnwindTable.cpp
index da88b0c..61d5119 100644
--- a/lldb/source/Symbol/UnwindTable.cpp
+++ b/lldb/source/Symbol/UnwindTable.cpp
@@ -86,6 +86,7 @@ void UnwindTable::Initialize() {
 void UnwindTable::ModuleWasUpdated() {
   std::lock_guard<std::mutex> guard(m_mutex);
   m_scanned_all_unwind_sources = false;
+  m_unwinds.clear();
 }
 
 UnwindTable::~UnwindTable() = default;
@@ -118,7 +119,7 @@ UnwindTable::GetAddressRange(const Address &addr, const SymbolContext &sc) {
 
 FuncUnwindersSP
 UnwindTable::GetFuncUnwindersContainingAddress(const Address &addr,
-                                               SymbolContext &sc) {
+                                               const SymbolContext &sc) {
   Initialize();
 
   std::lock_guard<std::mutex> guard(m_mutex);