[Lldb-commits] [lldb] [lldb][Expression] Emit a 'Note' diagnistc that indicates the language used for expression evaluation (PR #161688)
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Thu Oct 2 08:33:28 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Michael Buch (Michael137)
<details>
<summary>Changes</summary>
Since it's a 'Note' diagnostic it would only show up when expression evaluation actually failed. This helps with expression evaluation failure reports in mixed language environments where it's not quite clear what language the expression ran as. It may also reduce confusion around why the expression evaluator ran an expression in a language it wasn't asked to run (a softer alternative to what I attempted in https://github.com/llvm/llvm-project/pull/156648).
Here are some example outputs:
```
(lldb) expr -l c -- blah
˄
╰─ error: use of undeclared identifier 'blah'
note: Requested expression evaluation as 'c' but fell back to 'c++'.
(lldb) expr -l c++ -- blah
˄
╰─ error: use of undeclared identifier 'blah'
note: Requested expression evaluation as c++
(lldb) expr -l objc -- blah
˄
╰─ error: use of undeclared identifier 'blah'
note: Requested expression evaluation as 'objective-c' but fell back to 'objective-c++'.
(lldb) expr -l rust -- blah
˄
╰─ error: use of undeclared identifier 'blah'
note: Requested expression evaluation as rust
```
I didn't put the diagnostic on the same line as the inline diagnostic for now because of implementation convenience, but if reviewers deem that a blocker I can take a stab at that again.
Also, other language plugins (namely Swift), won't immediately benefit from this and will have to emit their own diagnistc. I played around with having a virtual API on `UserExpression` or `ExpressionParser` that will be called consistently, but by the time we're about to parse the expression we are already several frames deep into the plugin. Before (and at the beginning of) the generic `UserExpression::Parse` call we don't have enough information to notify which language we're going to parse in (at least for the C++ plugin).
rdar://160297649
rdar://159669244
---
Full diff: https://github.com/llvm/llvm-project/pull/161688.diff
5 Files Affected:
- (modified) lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp (+25-4)
- (modified) lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h (+1)
- (modified) lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp (+2-2)
- (modified) lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp (+2-2)
- (modified) lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp (+1-1)
``````````diff
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
index 924953cc43fa2..77a8afa511a6a 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
@@ -74,6 +74,7 @@
#include "lldb/Core/Debugger.h"
#include "lldb/Core/Disassembler.h"
#include "lldb/Core/Module.h"
+#include "lldb/Expression/DiagnosticManager.h"
#include "lldb/Expression/IRExecutionUnit.h"
#include "lldb/Expression/IRInterpreter.h"
#include "lldb/Host/File.h"
@@ -527,7 +528,8 @@ static void SetupTargetOpts(CompilerInstance &compiler,
static void SetupLangOpts(CompilerInstance &compiler,
ExecutionContextScope &exe_scope,
- const Expression &expr) {
+ const Expression &expr,
+ DiagnosticManager &diagnostic_manager) {
Log *log = GetLog(LLDBLog::Expressions);
// If the expression is being evaluated in the context of an existing stack
@@ -547,6 +549,8 @@ static void SetupLangOpts(CompilerInstance &compiler,
: lldb::eLanguageTypeUnknown),
lldb_private::Language::GetNameForLanguageType(language));
+ lldb::LanguageType language_for_note = language;
+
LangOptions &lang_opts = compiler.getLangOpts();
switch (language) {
@@ -560,12 +564,14 @@ static void SetupLangOpts(CompilerInstance &compiler,
// family language, because the expression parser uses features of C++ to
// capture values.
lang_opts.CPlusPlus = true;
+ language_for_note = lldb::eLanguageTypeC_plus_plus;
break;
case lldb::eLanguageTypeObjC:
lang_opts.ObjC = true;
// FIXME: the following language option is a temporary workaround,
// to "ask for ObjC, get ObjC++" (see comment above).
lang_opts.CPlusPlus = true;
+ language_for_note = lldb::eLanguageTypeObjC_plus_plus;
// Clang now sets as default C++14 as the default standard (with
// GNU extensions), so we do the same here to avoid mismatches that
@@ -610,6 +616,21 @@ static void SetupLangOpts(CompilerInstance &compiler,
break;
}
+ if (language_for_note != language)
+ diagnostic_manager.AddDiagnostic(
+ llvm::formatv(
+ "Requested expression evaluation as '{0}' but fell back to '{1}'.",
+ lldb_private::Language::GetNameForLanguageType(language),
+ lldb_private::Language::GetNameForLanguageType(language_for_note))
+ .str(),
+ lldb::Severity::eSeverityInfo, DiagnosticOrigin::eDiagnosticOriginLLDB);
+ else
+ diagnostic_manager.AddDiagnostic(
+ llvm::formatv("Requested expression evaluation as '{0}'",
+ lldb_private::Language::GetNameForLanguageType(language))
+ .str(),
+ lldb::Severity::eSeverityInfo, DiagnosticOrigin::eDiagnosticOriginLLDB);
+
lang_opts.Bool = true;
lang_opts.WChar = true;
lang_opts.Blocks = true;
@@ -687,8 +708,8 @@ static void SetupImportStdModuleLangOpts(CompilerInstance &compiler,
ClangExpressionParser::ClangExpressionParser(
ExecutionContextScope *exe_scope, Expression &expr,
- bool generate_debug_info, std::vector<std::string> include_directories,
- std::string filename)
+ bool generate_debug_info, DiagnosticManager &diagnostic_manager,
+ std::vector<std::string> include_directories, std::string filename)
: ExpressionParser(exe_scope, expr, generate_debug_info), m_compiler(),
m_pp_callbacks(nullptr),
m_include_directories(std::move(include_directories)),
@@ -754,7 +775,7 @@ ClangExpressionParser::ClangExpressionParser(
}
// 4. Set language options.
- SetupLangOpts(*m_compiler, *exe_scope, expr);
+ SetupLangOpts(*m_compiler, *exe_scope, expr, diagnostic_manager);
auto *clang_expr = dyn_cast<ClangUserExpression>(&m_expr);
if (clang_expr && clang_expr->DidImportCxxModules()) {
LLDB_LOG(log, "Adding lang options for importing C++ modules");
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
index 93e0b007dbcc8..734ad51c9646e 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
@@ -65,6 +65,7 @@ class ClangExpressionParser : public ExpressionParser {
/// diagnostics (i.e. errors, warnings or notes from Clang).
ClangExpressionParser(ExecutionContextScope *exe_scope, Expression &expr,
bool generate_debug_info,
+ DiagnosticManager &diagnostic_manager,
std::vector<std::string> include_directories = {},
std::string filename = "<clang expression>");
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
index e4a094f3aa512..d2db319afb7a0 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
@@ -189,8 +189,8 @@ ClangFunctionCaller::CompileFunction(lldb::ThreadSP thread_to_use_sp,
lldb::ProcessSP jit_process_sp(m_jit_process_wp.lock());
if (jit_process_sp) {
const bool generate_debug_info = true;
- auto *clang_parser = new ClangExpressionParser(jit_process_sp.get(), *this,
- generate_debug_info);
+ auto *clang_parser = new ClangExpressionParser(
+ jit_process_sp.get(), *this, generate_debug_info, diagnostic_manager);
num_errors = clang_parser->Parse(diagnostic_manager);
m_parser.reset(clang_parser);
} else {
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
index 6b743e29e21f6..e8d5ec3c7fd96 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
@@ -574,7 +574,7 @@ bool ClangUserExpression::TryParse(
m_parser = std::make_unique<ClangExpressionParser>(
exe_ctx.GetBestExecutionContextScope(), *this, generate_debug_info,
- m_include_directories, m_filename);
+ diagnostic_manager, m_include_directories, m_filename);
unsigned num_errors = m_parser->Parse(diagnostic_manager);
@@ -818,7 +818,7 @@ bool ClangUserExpression::Complete(ExecutionContext &exe_ctx,
}
ClangExpressionParser parser(exe_ctx.GetBestExecutionContextScope(), *this,
- false);
+ false, diagnostic_manager);
// We have to find the source code location where the user text is inside
// the transformed expression code. When creating the transformed text, we
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
index 1f44200c4cff8..e6983066a12fa 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
@@ -120,7 +120,7 @@ bool ClangUtilityFunction::Install(DiagnosticManager &diagnostic_manager,
const bool generate_debug_info = true;
ClangExpressionParser parser(exe_ctx.GetBestExecutionContextScope(), *this,
- generate_debug_info);
+ generate_debug_info, diagnostic_manager);
unsigned num_errors = parser.Parse(diagnostic_manager);
``````````
</details>
https://github.com/llvm/llvm-project/pull/161688
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