[Lldb-commits] [lldb] [lldb] Fix dwim-print to not delete non-result persistent variables (PR #85152)

[Dave Lee via lldb-commits]

https://github.com/kastiglione created https://github.com/llvm/llvm-project/pull/85152

None

>From 970cf82fa3d64c5a4e1b3929c110b42974ef13cd Mon Sep 17 00:00:00 2001
From: Dave Lee <davelee.com at gmail.com>
Date: Wed, 13 Mar 2024 14:49:23 -0700
Subject: [PATCH] [lldb] Fix dwim-print to not delete non-result persistent
 variables

---
 lldb/source/Commands/CommandObjectDWIMPrint.cpp    | 12 ++++++++++--
 lldb/test/API/commands/dwim-print/TestDWIMPrint.py | 12 ++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/lldb/source/Commands/CommandObjectDWIMPrint.cpp b/lldb/source/Commands/CommandObjectDWIMPrint.cpp
index b183cb423111fb..5c043dfd101be6 100644
--- a/lldb/source/Commands/CommandObjectDWIMPrint.cpp
+++ b/lldb/source/Commands/CommandObjectDWIMPrint.cpp
@@ -170,6 +170,14 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
     ExpressionResults expr_result = target.EvaluateExpression(
         expr, exe_scope, valobj_sp, eval_options, &fixed_expression);
 
+    auto persistent_name = valobj_sp->GetName();
+    // EvaluateExpression doesn't generate a new persistent result (`$0`) when
+    // the expression is already just a persistent variable (`$var`). Instead,
+    // the same persistent variable is reused. Take note of when a persistent
+    // result is created, to prevent unintentional deletion of a user's
+    // persistent variable.
+    bool did_persist_result = persistent_name != expr;
+
     // Only mention Fix-Its if the expression evaluator applied them.
     // Compiler errors refer to the final expression after applying Fix-It(s).
     if (!fixed_expression.empty() && target.GetEnableNotifyAboutFixIts()) {
@@ -199,9 +207,9 @@ void CommandObjectDWIMPrint::DoExecute(StringRef command,
         }
       }
 
-      if (suppress_result)
+      if (did_persist_result && suppress_result)
         if (auto result_var_sp =
-                target.GetPersistentVariable(valobj_sp->GetName())) {
+                target.GetPersistentVariable(persistent_name)) {
           auto language = valobj_sp->GetPreferredDisplayLanguage();
           if (auto *persistent_state =
                   target.GetPersistentExpressionStateForLanguage(language))
diff --git a/lldb/test/API/commands/dwim-print/TestDWIMPrint.py b/lldb/test/API/commands/dwim-print/TestDWIMPrint.py
index 040632096c70e7..c650b1e3533e08 100644
--- a/lldb/test/API/commands/dwim-print/TestDWIMPrint.py
+++ b/lldb/test/API/commands/dwim-print/TestDWIMPrint.py
@@ -146,3 +146,15 @@ def test_void_result(self):
             self, "// break here", lldb.SBFileSpec("main.c")
         )
         self.expect("dwim-print (void)15", matching=False, patterns=["(?i)error"])
+
+    def test_preserves_persistent_variables(self):
+        """Test dwim-print does not delete persistent variables."""
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self, "// break here", lldb.SBFileSpec("main.c")
+        )
+        self.expect("dwim-print int $i = 15")
+        # Run the same expression twice and verify success. This ensures the
+        # first command does not delete the persistent variable.
+        for _ in range(2):
+            self.expect("dwim-print $i", startstr="(int) 15")