[Lldb-commits] [lldb] a31a5da - Make sure Target::EvaluateExpression() passes up an error instead of silently dropping it.

[Adrian Prantl via lldb-commits]

Author: Adrian Prantl
Date: 2022-10-17T15:21:41-07:00
New Revision: a31a5da3c7d7393749a43dbc678fd28fb94d07f6

URL: https://github.com/llvm/llvm-project/commit/a31a5da3c7d7393749a43dbc678fd28fb94d07f6
DIFF: https://github.com/llvm/llvm-project/commit/a31a5da3c7d7393749a43dbc678fd28fb94d07f6.diff

LOG: Make sure Target::EvaluateExpression() passes up an error instead of silently dropping it.

When UserExpression::Evaluate() fails and doesn't return a ValueObject there is no vehicle for returning the error in the return value.

This behavior can be observed by applying the following patch:

diff --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index f1a311b7252c..58c03ccdb068 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -2370,6 +2370,7 @@ UserExpression *Target::GetUserExpressionForLanguage(
     Expression::ResultType desired_type,
     const EvaluateExpressionOptions &options, ValueObject *ctx_obj,
     Status &error) {
+  error.SetErrorStringWithFormat("Ha ha!");  return nullptr;
   auto type_system_or_err = GetScratchTypeSystemForLanguage(language);
   if (auto err = type_system_or_err.takeError()) {
     error.SetErrorStringWithFormat(

and then running

$ lldb -o "p 1"
(lldb) p 1
(lldb)

This patch fixes this by creating an empty result ValueObject that wraps the error.

Differential Revision: https://reviews.llvm.org/D135998

Added: 
    

Modified: 
    lldb/source/Commands/CommandObjectExpression.cpp
    lldb/source/Target/Target.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index b7d129e1d7df..be306f20881d 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -461,6 +461,8 @@ bool CommandObjectExpression::EvaluateExpression(llvm::StringRef expr,
         result.SetStatus(eReturnStatusFailed);
       }
     }
+  } else {
+    error_stream.Printf("error: unknown error\n");
   }
 
   return (success != eExpressionSetupError &&

diff  --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index c567407757e3..f1a311b7252c 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -26,6 +26,7 @@
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/StructuredDataImpl.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Core/ValueObjectConstResult.h"
 #include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
 #include "lldb/Expression/REPL.h"
@@ -2528,6 +2529,10 @@ ExpressionResults Target::EvaluateExpression(
     execution_results = UserExpression::Evaluate(exe_ctx, options, expr, prefix,
                                                  result_valobj_sp, error,
                                                  fixed_expression, ctx_obj);
+    // Pass up the error by wrapping it inside an error result.
+    if (error.Fail() && !result_valobj_sp)
+      result_valobj_sp = ValueObjectConstResult::Create(
+          exe_ctx.GetBestExecutionContextScope(), error);
   }
 
   if (execution_results == eExpressionCompleted)