[Lldb-commits] [lldb] 6a4905a - [lldb] Mark expressions that couldn't be parsed or executed as failed expressions

[Raphael Isemann via lldb-commits]

Author: Raphael Isemann
Date: 2020-03-23T15:28:17+01:00
New Revision: 6a4905ae2d65a2883112bf8cbf83c35c0c03f410

URL: https://github.com/llvm/llvm-project/commit/6a4905ae2d65a2883112bf8cbf83c35c0c03f410
DIFF: https://github.com/llvm/llvm-project/commit/6a4905ae2d65a2883112bf8cbf83c35c0c03f410.diff

LOG: [lldb] Mark expressions that couldn't be parsed or executed as failed expressions

Summary:
LLDB keeps statistics of how many expression evaluations are 'successful' and 'failed'
which are updated after each expression evaluation (assuming statistics are enabled).
>From what I understand the idea is that this could be used to define how well LLDB's
expression evaluator is working.

Currently all expressions are considered successful unless the user passes an explicit
positive element counting to the expression command (with the `-Z` flag) and then passes
an expression that successfully evaluates to a type that doesn't support element counting.
Expressions that fail to parse, execute or any other outcome are considered successful
at the moment which means we nearly always have a 100% expression evaluation
success rate.

This patch makes that expressions that fail to parse or execute to count as failed
expressions.

We can't know whether the expression failed because of an user error
of because LLDB couldn't correctly parse/compile it, but I would argue that this is
still an improvement. Assuming that the percentage of valid user expressions stays
mostly constant over time (which seems like a reasonable assumption), then this
way we can still see if we are doing relatively better/worse from release to release.

Reviewers: davide, aprantl, JDevlieghere

Reviewed By: aprantl

Subscribers: abidh

Differential Revision: https://reviews.llvm.org/D76280

Added: 
    

Modified: 
    lldb/source/Commands/CommandObjectExpression.cpp
    lldb/source/Commands/CommandObjectExpression.h
    lldb/test/API/commands/statistics/basic/TestStats.py

Removed: 
    


################################################################################
diff  --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index 7d8de573df0e..9a314c251475 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -486,7 +486,8 @@ bool CommandObjectExpression::EvaluateExpression(llvm::StringRef expr,
     }
   }
 
-  return true;
+  return (success != eExpressionSetupError &&
+          success != eExpressionParseError);
 }
 
 void CommandObjectExpression::IOHandlerInputComplete(IOHandler &io_handler,

diff  --git a/lldb/source/Commands/CommandObjectExpression.h b/lldb/source/Commands/CommandObjectExpression.h
index ddee9c36924d..1e59cbc14528 100644
--- a/lldb/source/Commands/CommandObjectExpression.h
+++ b/lldb/source/Commands/CommandObjectExpression.h
@@ -71,6 +71,16 @@ class CommandObjectExpression : public CommandObjectRaw,
   /// expression in the given target.
   EvaluateExpressionOptions GetEvalOptions(const Target &target);
 
+  /// Evaluates the given expression.
+  /// \param output_stream The stream to which the evaluation result will be
+  ///                      printed.
+  /// \param error_stream Contains error messages that should be displayed to
+  ///                     the user in case the evaluation fails.
+  /// \param result A CommandReturnObject which status will be set to the
+  ///               appropriate value depending on evaluation success and
+  ///               whether the expression produced any result.
+  /// \return Returns true iff the expression was successfully evaluated,
+  ///         executed and the result could be printed to the output stream.
   bool EvaluateExpression(llvm::StringRef expr, Stream &output_stream,
                           Stream &error_stream, CommandReturnObject &result);
 

diff  --git a/lldb/test/API/commands/statistics/basic/TestStats.py b/lldb/test/API/commands/statistics/basic/TestStats.py
index 76bc22433848..be028199fade 100644
--- a/lldb/test/API/commands/statistics/basic/TestStats.py
+++ b/lldb/test/API/commands/statistics/basic/TestStats.py
@@ -21,6 +21,20 @@ def test(self):
         self.expect("statistics dump", substrs=['expr evaluation successes : 1\n',
                                                 'expr evaluation failures : 0\n'])
 
+        self.expect("statistics enable")
+        # Doesn't parse.
+        self.expect("expr doesnt_exist", error=True,
+                    substrs=["undeclared identifier 'doesnt_exist'"])
+        # Doesn't successfully execute.
+        self.expect("expr int *i = nullptr; *i", error=True)
+        # Interpret an integer as an array with 3 elements is also a failure.
+        self.expect("expr -Z 3 -- 1", error=True,
+                    substrs=["expression cannot be used with --element-count"])
+        self.expect("statistics disable")
+        # We should have gotten 3 new failures and the previous success.
+        self.expect("statistics dump", substrs=['expr evaluation successes : 1\n',
+                                                'expr evaluation failures : 3\n'])
+
         # 'frame var' with disabled statistics shouldn't change stats.
         self.expect("frame var", substrs=['27'])