[Lldb-commits] [lldb] [lldb][Expression] Reject languages not supported by TypeSystems for expression evaluation (PR #156648)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

<details>
<summary>Changes</summary>

There are some languages for which the `ClangExpressionParser` currently switches the language type behind a user's back. Specifically, `C` gets turned into `C++` and `ObjC` into `ObjC++`. That's because the Clang expression evaluator depends on C++ features. These languages have different semantics, so if, e.g., a user forcefully wants to evaluate an expression in `C`, but we switch it to `C++`, they will most likely wonder why the expression failed (we get reports like this every once in a while...https://github.com/llvm/llvm-project/issues/152113 is a variation of this).

This patch rejects languages specified with `expression --language` that we won't be able to explicitly evaluate.

rdar://159669244

---
Full diff: https://github.com/llvm/llvm-project/pull/156648.diff


3 Files Affected:

- (modified) lldb/source/Commands/CommandObjectExpression.cpp (+17-9) 
- (modified) lldb/test/API/commands/expression/calculator_mode/TestCalculatorMode.py (+1-1) 
- (modified) lldb/test/API/commands/expression/invalid-args/TestInvalidArgsExpression.py (+14-2) 


``````````diff
diff --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index 197bffe9c982f..1b951603563ac 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -44,18 +44,26 @@ Status CommandObjectExpression::CommandOptions::SetOptionValue(
   const int short_option = GetDefinitions()[option_idx].short_option;
 
   switch (short_option) {
-  case 'l':
+  case 'l': {
     language = Language::GetLanguageTypeFromString(option_arg);
-    if (language == eLanguageTypeUnknown) {
-      StreamString sstr;
-      sstr.Printf("unknown language type: '%s' for expression. "
-                  "List of supported languages:\n",
+    if (const LanguageSet supported_languages =
+            Language::GetLanguagesSupportingTypeSystemsForExpressions();
+        supported_languages[language])
+      break;
+
+    StreamString sstr;
+    if (language == eLanguageTypeUnknown)
+      sstr.Printf("unknown language '%s' for expression. ",
+                  option_arg.str().c_str());
+    else
+      sstr.Printf("language '%s' is currently not supported for expression "
+                  "evaluation. ",
                   option_arg.str().c_str());
 
-      Language::PrintSupportedLanguagesForExpressions(sstr, "  ", "\n");
-      error = Status(sstr.GetString().str());
-    }
-    break;
+    sstr.PutCString("List of supported languages for expressions:\n");
+    Language::PrintSupportedLanguagesForExpressions(sstr, "  ", "\n");
+    error = Status(sstr.GetString().str());
+  } break;
 
   case 'a': {
     bool success;
diff --git a/lldb/test/API/commands/expression/calculator_mode/TestCalculatorMode.py b/lldb/test/API/commands/expression/calculator_mode/TestCalculatorMode.py
index 138027507c7a7..f12b5b0a12814 100644
--- a/lldb/test/API/commands/expression/calculator_mode/TestCalculatorMode.py
+++ b/lldb/test/API/commands/expression/calculator_mode/TestCalculatorMode.py
@@ -21,7 +21,7 @@ def test__calculator_mode(self):
         )
         # Now try it with a specific language:
         self.expect(
-            "expression -l c -- 11 + 22",
+            "expression -l c++ -- 11 + 22",
             "11 + 22 didn't get the expected result",
             substrs=["33"],
         )
diff --git a/lldb/test/API/commands/expression/invalid-args/TestInvalidArgsExpression.py b/lldb/test/API/commands/expression/invalid-args/TestInvalidArgsExpression.py
index 344aef318d783..f0d1542d783b1 100644
--- a/lldb/test/API/commands/expression/invalid-args/TestInvalidArgsExpression.py
+++ b/lldb/test/API/commands/expression/invalid-args/TestInvalidArgsExpression.py
@@ -10,8 +10,20 @@ def test_invalid_lang(self):
             "expression -l foo --",
             error=True,
             substrs=[
-                "error: unknown language type: 'foo' for expression",
-                "List of supported languages:",
+                "error: unknown language 'foo' for expression.",
+                "List of supported languages for expressions:",
+                "c++",
+                "c++11",
+                "c++14",
+            ],
+        )
+
+        self.expect(
+            "expression -l c --",
+            error=True,
+            substrs=[
+                "error: language 'c' is currently not supported for expression evaluation.",
+                "List of supported languages for expressions:",
                 "c++",
                 "c++11",
                 "c++14",

``````````

</details>


https://github.com/llvm/llvm-project/pull/156648