[clang] 8a4d388 - [Clang][Sema] Prohibit statement expression in the default argument
Jun Zhang via cfe-commits
cfe-commits at lists.llvm.org
Tue Apr 5 18:29:49 PDT 2022
Author: Jun Zhang
Date: 2022-04-06T09:28:20+08:00
New Revision: 8a4d388c7fa47fa50076babecc38757009dbc987
URL: https://github.com/llvm/llvm-project/commit/8a4d388c7fa47fa50076babecc38757009dbc987
DIFF: https://github.com/llvm/llvm-project/commit/8a4d388c7fa47fa50076babecc38757009dbc987.diff
LOG: [Clang][Sema] Prohibit statement expression in the default argument
As statement expression makes no sense in the default argument,
this patch tries to disable it in the all cases.
Please note that the statement expression is a GNU extension, which
means that Clang should be consistent with GCC. However, there's no
response from GCC devs since we have raised the issue for several weeks.
In this case, I think we can disallow statement expressions as a default
parameter in general for now, and relax the restriction if GCC folks
decide to retain the feature for functions but not lambdas in the
future.
Related discussion: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104765
Fixes https://github.com/llvm/llvm-project/issues/53488
Differential Revision: https://reviews.llvm.org/D119609
Added:
clang/test/Sema/stmt-expr-in-default-arg.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Parse/ParseDecl.cpp
clang/lib/Parse/ParseTemplate.cpp
clang/test/SemaTemplate/dependent-expr.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 86d0a3e7303f1..bf592329ac02a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -97,6 +97,8 @@ Bug Fixes
- The builtin function __builtin_dump_struct would crash clang when the target
struct contains a bitfield. It now correctly handles bitfields.
This fixes Issue `Issue 54462 <https://github.com/llvm/llvm-project/issues/54462>`_.
+- Statement expressions are now disabled in default arguments in general.
+ This fixes Issue `Issue 53488 <https://github.com/llvm/llvm-project/issues/53488>`_.
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index c5171359e7e4c..96cd00c8bb2a1 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -4380,6 +4380,9 @@ def err_uninitialized_member_in_ctor : Error<
def err_default_arg_makes_ctor_special : Error<
"addition of default argument on redeclaration makes this constructor a "
"%select{default|copy|move}0 constructor">;
+def err_stmt_expr_in_default_arg : Error<
+ "default %select{argument|non-type template argument}0 may not use a GNU "
+ "statement expression">;
def err_use_of_default_argument_to_function_declared_later : Error<
"use of default argument to function %0 that is declared later in class %1">;
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index f07758197205f..627b11fb6ac0c 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -7066,8 +7066,16 @@ void Parser::ParseParameterDeclarationClause(
if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace)) {
Diag(Tok, diag::warn_cxx98_compat_generalized_initializer_lists);
DefArgResult = ParseBraceInitializer();
- } else
+ } else {
+ if (Tok.is(tok::l_paren) && NextToken().is(tok::l_brace)) {
+ Diag(Tok, diag::err_stmt_expr_in_default_arg) << 0;
+ Actions.ActOnParamDefaultArgumentError(Param, EqualLoc);
+ // Skip the statement expression and continue parsing
+ SkipUntil(tok::comma, StopBeforeMatch);
+ continue;
+ }
DefArgResult = ParseAssignmentExpression();
+ }
DefArgResult = Actions.CorrectDelayedTyposInExpr(DefArgResult);
if (DefArgResult.isInvalid()) {
Actions.ActOnParamDefaultArgumentError(Param, EqualLoc);
diff --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index 211d1a33542b2..5687882251a05 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -19,6 +19,7 @@
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
+#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/Support/TimeProfiler.h"
using namespace clang;
@@ -1007,18 +1008,23 @@ Parser::ParseNonTypeTemplateParameter(unsigned Depth, unsigned Position) {
SourceLocation EqualLoc;
ExprResult DefaultArg;
if (TryConsumeToken(tok::equal, EqualLoc)) {
- // C++ [temp.param]p15:
- // When parsing a default template-argument for a non-type
- // template-parameter, the first non-nested > is taken as the
- // end of the template-parameter-list rather than a greater-than
- // operator.
- GreaterThanIsOperatorScope G(GreaterThanIsOperator, false);
- EnterExpressionEvaluationContext ConstantEvaluated(
- Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
-
- DefaultArg = Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
- if (DefaultArg.isInvalid())
+ if (Tok.is(tok::l_paren) && NextToken().is(tok::l_brace)) {
+ Diag(Tok.getLocation(), diag::err_stmt_expr_in_default_arg) << 1;
SkipUntil(tok::comma, tok::greater, StopAtSemi | StopBeforeMatch);
+ } else {
+ // C++ [temp.param]p15:
+ // When parsing a default template-argument for a non-type
+ // template-parameter, the first non-nested > is taken as the
+ // end of the template-parameter-list rather than a greater-than
+ // operator.
+ GreaterThanIsOperatorScope G(GreaterThanIsOperator, false);
+ EnterExpressionEvaluationContext ConstantEvaluated(
+ Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+ DefaultArg =
+ Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
+ if (DefaultArg.isInvalid())
+ SkipUntil(tok::comma, tok::greater, StopAtSemi | StopBeforeMatch);
+ }
}
// Create the parameter.
diff --git a/clang/test/Sema/stmt-expr-in-default-arg.cpp b/clang/test/Sema/stmt-expr-in-default-arg.cpp
new file mode 100644
index 0000000000000..85bb8aa428993
--- /dev/null
+++ b/clang/test/Sema/stmt-expr-in-default-arg.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 %s -fsyntax-only -verify -std=c++20
+
+void foo() {
+ void fn(int i, int = ({ 1; })); // expected-error {{default argument may not use a GNU statement expression}}
+
+ auto a = [](int = ({ 1; })) {}; // expected-error {{default argument may not use a GNU statement expression}}
+
+ auto b = []<int = ({ 1; })>(){}; // expected-error {{default non-type template argument may not use a GNU statement expression}}
+
+ void fn(int i, int j = ({{}, {}, {,}}), int k = ""); // expected-error {{default argument may not use a GNU statement expression}} expected-error {{cannot initialize a parameter of type 'int' with an lvalue of type 'const char[1]'}} expected-note {{passing argument to parameter 'k' here}}
+}
+
+template <int foo = ({ 1; })> // expected-error {{default non-type template argument may not use a GNU statement expression}}
+void f() {}
+
+template <int bar = ({ 1; })> // expected-error {{default non-type template argument may not use a GNU statement expression}}
+class S {};
+
+template <typename Callable>
+int bar(Callable &&Call) {
+ return Call();
+}
+
+int baz() {
+ auto l = [](int a = ({ int x = 12; x; })) { // expected-error {{default argument may not use a GNU statement expression}}
+ return 1;
+ };
+ return bar(l);
+}
diff --git a/clang/test/SemaTemplate/dependent-expr.cpp b/clang/test/SemaTemplate/dependent-expr.cpp
index abdb8e9c4a9fd..51bd375d7920e 100644
--- a/clang/test/SemaTemplate/dependent-expr.cpp
+++ b/clang/test/SemaTemplate/dependent-expr.cpp
@@ -141,15 +141,7 @@ namespace PR45083 {
using U = float; // expected-error {{
diff erent types ('float' vs 'decltype(g<int>())' (aka 'void'))}}
void h(auto a, decltype(g<char>())*) {} // expected-note {{previous}}
- void h(auto a, void*) {} // expected-error {{redefinition}}
-
- void i(auto a) {
- [](auto a, int = ({decltype(a) i; i * 2;})){}(a); // expected-error {{invalid operands to binary expression ('decltype(a)' (aka 'void *') and 'int')}} expected-note {{in instantiation of}}
- }
- void use_i() {
- i(0);
- i((void*)0); // expected-note {{instantiation of}}
- }
+ void h(auto a, void *) {} // expected-error {{redefinition}}
}
namespace BindingInStmtExpr {
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