[lldb] Fallback to expression eval when Dump of variable fails in dwim-print

[kastiglione]

Previously, when dwim-print finds a frame variables, it returns immediately after calling Dump, even if Dump returns an error. This is most likely to happen when evaluating an object description, ie po.

This changes dwim-print to continue on to expression evaluation when Dumping a variable returns an error . This is to allow for more complete diagnostics when po fails.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Dave Lee (kastiglione)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/151374.diff

1 Files Affected:

• (modified) lldb/source/Commands/CommandObjectDWIMPrint.cpp (+20-18)

diff --git a/lldb/source/Commands/CommandObjectDWIMPrint.cpp b/lldb/source/Commands/CommandObjectDWIMPrint.cpp
index a2c004d0ee97f..5b788d7d0c5a2 100644
--- a/lldb/source/Commands/CommandObjectDWIMPrint.cpp
+++ b/lldb/source/Commands/CommandObjectDWIMPrint.cpp
@@ -23,6 +23,7 @@
 #include "lldb/lldb-enumerations.h"
 #include "lldb/lldb-forward.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
 
 #include <regex>
 
@@ -132,27 +133,22 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
   };
 
   // Dump `valobj` according to whether `po` was requested or not.
-  auto dump_val_object = [&](ValueObject &valobj) {
+  auto dump_val_object = [&](ValueObject &valobj) -> Error {
     if (is_po) {
       StreamString temp_result_stream;
-      if (llvm::Error error = valobj.Dump(temp_result_stream, dump_options)) {
-        result.AppendError(toString(std::move(error)));
-        return;
-      }
+      if (Error err = valobj.Dump(temp_result_stream, dump_options))
+        return err;
       llvm::StringRef output = temp_result_stream.GetString();
       maybe_add_hint(output);
       result.GetOutputStream() << output;
     } else {
-      llvm::Error error =
-        valobj.Dump(result.GetOutputStream(), dump_options);
-      if (error) {
-        result.AppendError(toString(std::move(error)));
-        return;
-      }
+      if (Error err = valobj.Dump(result.GetOutputStream(), dump_options))
+        return err;
     }
     m_interpreter.PrintWarningsIfNecessary(result.GetOutputStream(),
                                            m_cmd_name);
     result.SetStatus(eReturnStatusSuccessFinishResult);
+    return Error::success();
   };
 
   // First, try `expr` as a _limited_ frame variable expression path: only the
@@ -186,8 +182,11 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
                                      expr);
       }
 
-      dump_val_object(*valobj_sp);
-      return;
+      bool failed = errorToBool(dump_val_object(*valobj_sp));
+      if (!failed)
+        return;
+
+      // Dump failed, continue on to expression evaluation.
     }
   }
 
@@ -196,8 +195,9 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
     if (auto *state = target.GetPersistentExpressionStateForLanguage(language))
       if (auto var_sp = state->GetVariable(expr))
         if (auto valobj_sp = var_sp->GetValueObject()) {
-          dump_val_object(*valobj_sp);
-          return;
+          bool failed = errorToBool(dump_val_object(*valobj_sp));
+          if (!failed)
+            return;
         }
 
   // Third, and lastly, try `expr` as a source expression to evaluate.
@@ -248,10 +248,12 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
       result.AppendNoteWithFormatv("ran `expression {0}{1}`", flags, expr);
     }
 
-    if (valobj_sp->GetError().GetError() != UserExpression::kNoResult)
-      dump_val_object(*valobj_sp);
-    else
+    if (valobj_sp->GetError().GetError() != UserExpression::kNoResult) {
+      if (Error err = dump_val_object(*valobj_sp))
+        result.SetError(std::move(err));
+    } else {
       result.SetStatus(eReturnStatusSuccessFinishNoResult);
+    }
 
     if (suppress_result)
       if (auto result_var_sp =

[augusto2112]

I'm confused about the order of the arguments to this macro. The error comes first, then the format string, then the other parameter?

[kastiglione]

yup – error, format, params