From 68d704844575d166301cf579b77b947fbe3446bb Mon Sep 17 00:00:00 2001 From: Michael Buch Date: Fri, 6 Feb 2026 16:44:49 +0000 Subject: [PATCH] [lldb][ClangUserExpression] Emit workaround hint when trying to call function templates (#179916) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Before: ``` (lldb) expression some_template_func(5) ˄ ╰─ error: 'some_template_func' does not name a template but is followed by template arguments note: Ran expression as 'C++14'. note: note: non-template declaration found by name lookup ``` After: ``` (lldb) expression some_template_func(5) ˄ ╰─ error: 'some_template_func' does not name a template but is followed by template arguments note: Ran expression as 'C++14'. note: note: non-template declaration found by name lookup note: Naming template instantiation not yet supported. Template functions can be invoked via their mangled name. E.g., expression _Z3fooIiEvi(5) ``` There isn't a great way to get to the actual function being named (and its mangled name) since we're just dealing with raw text. So I just print an example mangled name. This doesn't work for all template instantiations. E.g.,: ``` (lldb) p f.method(10) ˄ ˄ │ ╰─ error: expected '(' for function-style cast or type construction ╰─ error: no member named 'method' in 'Foo' note: Ran expression as 'C++14'. ``` This is a consequence of how we construct the AST for template methods. Once we fix that, this hint will get emitted there too. Note this will also trigger in cases where no function is being called (hence I used the defensive phrase "Template functions can be invoked"). rdar://135725807 --- .../Clang/ClangUserExpression.cpp | 25 ++++++++++ .../Clang/ClangUserExpression.h | 3 ++ .../cpp/template-diagnostic-hint/Makefile | 3 ++ .../TestTemplateDiagnosticHint.py | 48 +++++++++++++++++++ .../cpp/template-diagnostic-hint/main.cpp | 14 ++++++ 5 files changed, 93 insertions(+) create mode 100644 lldb/test/API/lang/cpp/template-diagnostic-hint/Makefile create mode 100644 lldb/test/API/lang/cpp/template-diagnostic-hint/TestTemplateDiagnosticHint.py create mode 100644 lldb/test/API/lang/cpp/template-diagnostic-hint/main.cpp diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp index 239280c65255..4fcc640d9071 100644 --- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp +++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp @@ -56,6 +56,7 @@ #include "clang/AST/DeclCXX.h" #include "clang/AST/DeclObjC.h" +#include "clang/Basic/DiagnosticSema.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/ScopeExit.h" #include "llvm/BinaryFormat/Dwarf.h" @@ -988,9 +989,33 @@ void ClangUserExpression::FixupCVRParseErrorDiagnostics( !m_fixed_text.empty() ? m_fixed_text.c_str() : m_expr_text.c_str()); } +void ClangUserExpression::FixupTemplateLookupDiagnostics( + DiagnosticManager &diagnostic_manager) const { + if (llvm::none_of(diagnostic_manager.Diagnostics(), + [](std::unique_ptr const &diag) { + switch (diag->GetCompilerID()) { + // FIXME: should we also be checking + // clang::diag::err_no_member_template? + case clang::diag::err_no_template: + case clang::diag::err_non_template_in_template_id: + return true; + default: + return false; + } + })) + return; + + diagnostic_manager.AddDiagnostic( + "Naming template instantiation not yet supported. Template functions " + "can be invoked via their mangled name. For example, using " + "`_Z3fooIiEvi(123)` for `foo(123)`", + lldb::eSeverityInfo, eDiagnosticOriginLLDB); +} + void ClangUserExpression::FixupParseErrorDiagnostics( DiagnosticManager &diagnostic_manager) const { FixupCVRParseErrorDiagnostics(diagnostic_manager); + FixupTemplateLookupDiagnostics(diagnostic_manager); } char ClangUserExpression::ClangUserExpressionHelper::ID; diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h index fd24893b1ecd..74aceed1d637 100644 --- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h +++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h @@ -215,6 +215,9 @@ private: void FixupCVRParseErrorDiagnostics(DiagnosticManager &diagnostic_manager) const; + void + FixupTemplateLookupDiagnostics(DiagnosticManager &diagnostic_manager) const; + /// Defines how the current expression should be wrapped. ClangExpressionSourceCode::WrapKind GetWrapKind() const; bool SetupPersistentState(DiagnosticManager &diagnostic_manager, diff --git a/lldb/test/API/lang/cpp/template-diagnostic-hint/Makefile b/lldb/test/API/lang/cpp/template-diagnostic-hint/Makefile new file mode 100644 index 000000000000..99998b20bcb0 --- /dev/null +++ b/lldb/test/API/lang/cpp/template-diagnostic-hint/Makefile @@ -0,0 +1,3 @@ +CXX_SOURCES := main.cpp + +include Makefile.rules diff --git a/lldb/test/API/lang/cpp/template-diagnostic-hint/TestTemplateDiagnosticHint.py b/lldb/test/API/lang/cpp/template-diagnostic-hint/TestTemplateDiagnosticHint.py new file mode 100644 index 000000000000..e8287108f758 --- /dev/null +++ b/lldb/test/API/lang/cpp/template-diagnostic-hint/TestTemplateDiagnosticHint.py @@ -0,0 +1,48 @@ +import lldb +from lldbsuite.test.decorators import * +from lldbsuite.test.lldbtest import * +from lldbsuite.test import lldbutil + + +class TestCase(TestBase): + def test(self): + self.build() + (_, process, _, _) = lldbutil.run_to_source_breakpoint( + self, "main", lldb.SBFileSpec("main.cpp") + ) + + self.expect( + "expression some_template_func(5)", + error=True, + substrs=[ + "does not name a template but is followed by template arguments", + "note: Naming template instantiation not yet supported.", + "Template functions can be invoked via their mangled name.", + ], + ) + + self.expect( + "expression some_template_func(5) + some_template_func(5)", + error=True, + substrs=[ + "does not name a template but is followed by template arguments", + "does not name a template but is followed by template arguments", + ], + ) + + self.assertEqual( + self.res.GetError().count( + "note: Naming template instantiation not yet supported" + ), + 1, + ) + + self.expect( + "expression Foo::smethod()", + error=True, + substrs=[ + "no template named 'Foo'", + "note: Naming template instantiation not yet supported.", + "Template functions can be invoked via their mangled name.", + ], + ) diff --git a/lldb/test/API/lang/cpp/template-diagnostic-hint/main.cpp b/lldb/test/API/lang/cpp/template-diagnostic-hint/main.cpp new file mode 100644 index 000000000000..914d9b59484d --- /dev/null +++ b/lldb/test/API/lang/cpp/template-diagnostic-hint/main.cpp @@ -0,0 +1,14 @@ +template static K some_template_func(int x) { + return (K)x; +} + +template struct Foo { + template T method(K k) { return (T)k; } + static T smethod() { return (T)10; } +}; + +int main() { + Foo f; + return some_template_func(5) + Foo::smethod() + + f.method(10); +}