[PATCH] D65696: Implements CWG 2082 Referring to parameters in unevaluated operands of default arguments
rsmith added inline comments. Comment at: clang/lib/Sema/SemaDeclCXX.cpp:143-148 + /// CheckDefaultArgumentVisitorODR - C++ [dcl.fct.default] Traverses + /// the default argument of a parameter to determine whether it + /// contains ODR violations. These violations cannot be checked in + /// \ref CheckDefaultArgumentVisitor since the DeclRefExp's may be changed to + /// an implicit cast from an LValue to RValue by \ref SetParamDefaultArgument. + /// When that happens the ODR usage may be allowed. Instead of visiting the default argument twice, can we call `SetParamDefaultArgument` first before doing the checks? CHANGES SINCE LAST ACTION https://reviews.llvm.org/D65696/new/ https://reviews.llvm.org/D65696 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[PATCH] D65696: Implements CWG 2082 Referring to parameters in unevaluated operands of default arguments
Mordante updated this revision to Diff 215448.
Mordante added a comment.
Updated the unit tests as requested. This required the
`Sema::ActOnParamDefaultArgument` to delay a part of the ODR validation until
the default argument has been 'instantiated'.
As discussed on IRC; the up to date `cwg_index.html` is not public, so I only
updated the unit test and removed the changes to `cxx_dr_status.html`.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D65696/new/
https://reviews.llvm.org/D65696
Files:
clang/lib/Sema/SemaDeclCXX.cpp
clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
clang/test/CXX/drs/dr20xx.cpp
Index: clang/test/CXX/drs/dr20xx.cpp
===
--- clang/test/CXX/drs/dr20xx.cpp
+++ clang/test/CXX/drs/dr20xx.cpp
@@ -8,6 +8,76 @@
#define static_assert(...) _Static_assert(__VA_ARGS__)
#endif
+
+namespace dr2082 { // dr2082: 10
+namespace local_var {
+void g() {
+ int k = 42;
+ void l(int m = k); // expected-error {{default argument references local variable 'k' of enclosing function}}
+}
+} // namespace local_var
+namespace local_const {
+void g() {
+ const int k = 42;
+ void l(int m = k);
+}
+} // namespace local_const
+#if __cplusplus >= 201103L
+namespace local_constexpr {
+void g() {
+ constexpr int k = 42;
+ void l(int m = k);
+}
+} // namespace local_constexpr
+#endif
+
+namespace local_const_float_to_integral {
+void g() {
+ const double k = 42;
+ void l(int m = k); // expected-error {{default argument references local variable 'k' of enclosing function}}
+}
+} // namespace local_const_float_to_integral
+#if __cplusplus >= 201103L
+namespace local_constexpr_float_to_integral {
+void g() {
+ constexpr double k = 42;
+ void l(int m = k);
+}
+} // namespace local_constexpr_float_to_integral
+
+namespace local_member_const {
+struct a {
+ int b;
+ int c;
+};
+void g() {
+ const a n{42, 42};
+ void l(int m = n.b); // expected-error {{default argument references local variable 'n' of enclosing function}}
+}
+} // namespace local_member_const
+namespace local_member_constexpr {
+struct a {
+ int b;
+ int c;
+};
+void g() {
+ constexpr a n{42, 42};
+ void l(int m = n.b);
+}
+} // namespace local_member_constexpr
+namespace local_member_mutable {
+struct a {
+ int b;
+ mutable int c;
+};
+void g() {
+ constexpr a n{42, 42};
+ void l(int m = n.b); // expected-error {{default argument references local variable 'n' of enclosing function}}
+}
+} // namespace local_member_mutable
+#endif
+}
+
namespace dr2083 { // dr2083: partial
#if __cplusplus >= 201103L
void non_const_mem_ptr() {
Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
===
--- clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
+++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
@@ -1,7 +1,8 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s
-void h()
+void f()
{
int i;
- extern void h2(int x = sizeof(i)); // expected-error {{default argument references local variable 'i' of enclosing function}}
+ extern void g(int x = i); // expected-error {{default argument references local variable 'i' of enclosing function}}
+ extern void h(int x = sizeof(i));
}
Index: clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
===
--- /dev/null
+++ clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int a;
+int f(int a, int b = a); // expected-error {{default argument references parameter 'a'}}
+typedef int I;
+int g(float I, int b = I(2)); // expected-error {{called object type 'float' is not a function or function pointer}}
+int h(int a, int b = sizeof(a));
+
+int b;
+class X {
+ int a;
+ int mem1(int i = a); // expected-error {{invalid use of non-static data member 'a'}}
+ int mem2(int i = b);
+ static int b;
+};
+
+int f(int = 0);
+void h() {
+ int j = f(1);
+ int k = f();
+}
+int (*p1)(int) =
+int (*p2)() = // expected-error {{cannot initialize a variable of type 'int (*)()' with an rvalue of type 'int (*)(int)': different number of parameters (0 vs 1)}}
Index: clang/lib/Sema/SemaDeclCXX.cpp
===
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -86,29 +86,22 @@
NamedDecl *Decl = DRE->getDecl();
if (ParmVarDecl *Param = dyn_cast(Decl)) {
// C++ [dcl.fct.default]p9
- // Default arguments are evaluated each time the function is
- // called. The order of evaluation of function arguments is
- // unspecified. Consequently, parameters of a function shall not
- // be used in default argument expressions, even if they are not
- // evaluated. Parameters of a function declared before a default
-
[PATCH] D65696: Implements CWG 2082 Referring to parameters in unevaluated operands of default arguments
Mordante marked 2 inline comments as done.
Mordante added inline comments.
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:103-105
+ // A local variable cannot be odr-used (6.2) in a default argument.
+ if (DRE->isNonOdrUse() != NOUR_None)
+return false;
rsmith wrote:
> Please add tests for the distinction between "potentially-evaluated" and
> "odr-used" here, for example:
>
> ```
> void f() {
> const int n = 123;
> void g(int k = n); // ok, not an odr-use
> }
> ```
I added the test but unfortunately clang disagrees with you and considers `n`
ODR used.
I'll have look how to teach clang `n` is not ODR used.
Comment at: clang/www/cxx_dr_status.html:3
"http://www.w3.org/TR/html4/strict.dtd;>
rsmith wrote:
> Note that this is an auto-generated file. To update it, you need to add a
> test to the relevant file (`test/CXX/drs/dr20xx.cpp`) with a suitable comment
> (`// dr2082: 10` to mark this implemented in Clang 10), grab a recent
> `cwg_index.html` file, and run the `make_cxx_dr_status` script.
Thanks for the info, I'll have a look at it after I fix the ODR used part.
Repository:
rG LLVM Github Monorepo
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[PATCH] D65696: Implements CWG 2082 Referring to parameters in unevaluated operands of default arguments
rsmith added inline comments.
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:103-105
+ // A local variable cannot be odr-used (6.2) in a default argument.
+ if (DRE->isNonOdrUse() != NOUR_None)
+return false;
Please add tests for the distinction between "potentially-evaluated" and
"odr-used" here, for example:
```
void f() {
const int n = 123;
void g(int k = n); // ok, not an odr-use
}
```
Comment at: clang/www/cxx_dr_status.html:3
"http://www.w3.org/TR/html4/strict.dtd;>
Note that this is an auto-generated file. To update it, you need to add a test
to the relevant file (`test/CXX/drs/dr20xx.cpp`) with a suitable comment (`//
dr2082: 10` to mark this implemented in Clang 10), grab a recent
`cwg_index.html` file, and run the `make_cxx_dr_status` script.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
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https://reviews.llvm.org/D65696
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[PATCH] D65696: Implements CWG 2082 Referring to parameters in unevaluated operands of default arguments
Mordante created this revision.
Mordante added a reviewer: rsmith.
Mordante added a project: clang.
This implements the current standard wording for [dcl.fct.default]p9 and
[dcl.fct.default]p7. This has been changed by CWG 2082.
Note: I don't have access to the paper therefore I assume it retroactively
applies to all C++ standards.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D65696
Files:
clang/lib/Sema/SemaDeclCXX.cpp
clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
clang/www/cxx_dr_status.html
Index: clang/www/cxx_dr_status.html
===
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -12307,7 +12307,7 @@
http://wg21.link/cwg2082;>2082
CD4
Referring to parameters in unevaluated operands of default
arguments
-Unknown
+SVN
http://wg21.link/cwg2083;>2083
Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
===
--- clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
+++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
@@ -1,7 +1,8 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s
-void h()
+void f()
{
int i;
- extern void h2(int x = sizeof(i)); // expected-error {{default argument
references local variable 'i' of enclosing function}}
+ extern void g(int x = i); // expected-error {{default argument references
local variable 'i' of enclosing function}}
+ extern void h(int x = sizeof(i));
}
Index: clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
===
--- /dev/null
+++ clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p9.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int a;
+int f(int a, int b = a); // expected-error {{default argument references
parameter 'a'}}
+typedef int I;
+int g(float I, int b = I(2)); // expected-error {{called object type 'float'
is not a function or function pointer}}
+int h(int a, int b = sizeof(a));
+
+int b;
+class X {
+ int a;
+ int mem1(int i = a); // expected-error {{invalid use of non-static data
member 'a'}}
+ int mem2(int i = b);
+ static int b;
+};
+
+int f(int = 0);
+void h() {
+ int j = f(1);
+ int k = f();
+}
+int (*p1)(int) =
+int (*p2)() = // expected-error {{cannot initialize a variable of type
'int (*)()' with an rvalue of type 'int (*)(int)': different number of
parameters (0 vs 1)}}
Index: clang/lib/Sema/SemaDeclCXX.cpp
===
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -86,20 +86,24 @@
NamedDecl *Decl = DRE->getDecl();
if (ParmVarDecl *Param = dyn_cast(Decl)) {
// C++ [dcl.fct.default]p9
- // Default arguments are evaluated each time the function is
- // called. The order of evaluation of function arguments is
- // unspecified. Consequently, parameters of a function shall not
- // be used in default argument expressions, even if they are not
- // evaluated. Parameters of a function declared before a default
- // argument expression are in scope and can hide namespace and
- // class member names.
+ // A default argument is evaluated each time the function is called
+ // with no argument for the corresponding parameter. A parameter shall
+ // not appear as a potentially-evaluated expression in a default
+ // argument. Parameters of a function declared before a default
+ // argument are in scope and can hide namespace and class member
+ // names.
+ if (DRE->isNonOdrUse() == NOUR_Unevaluated)
+return false;
+
return S->Diag(DRE->getBeginLoc(),
diag::err_param_default_argument_references_param)
<< Param->getDeclName() << DefaultArg->getSourceRange();
} else if (VarDecl *VDecl = dyn_cast(Decl)) {
// C++ [dcl.fct.default]p7
- // Local variables shall not be used in default argument
- // expressions.
+ // A local variable cannot be odr-used (6.2) in a default argument.
+ if (DRE->isNonOdrUse() != NOUR_None)
+return false;
+
if (VDecl->isLocalVarDecl())
return S->Diag(DRE->getBeginLoc(),
diag::err_param_default_argument_references_local)
Index: clang/www/cxx_dr_status.html
===
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -12307,7 +12307,7 @@
http://wg21.link/cwg2082;>2082
CD4
Referring to parameters in unevaluated operands of default arguments
-Unknown
+SVN
http://wg21.link/cwg2083;>2083
Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct.default/p7.cpp
