* [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182]
@ 2020-07-14 8:50 Jakub Jelinek
2020-07-29 19:30 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Jakub Jelinek @ 2020-07-14 8:50 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
Hi!
For C++11 we already emit an error if a constexpr function doesn't contain
a return statement, because in C++11 that is the only thing it needs to
contain, but for C++14 we would normally issue a -Wreturn-type warning.
As mentioned by Jonathan, such constexpr functions are invalid, no
diagnostics required, because there doesn't exist any arguments for
which it would result in valid constant expression.
This raises it to an error in such cases. The !LAMBDA_TYPE_P case
is to avoid error on g++.dg/pr81194.C where the user didn't write
constexpr anywhere and the operator() is compiler generated.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-07-14 Jakub Jelinek <jakub@redhat.com>
PR c++/96182
* decl.c (finish_function): In constexpr functions other than
lambdas use for C++14 and later error instead of warning if no
return statement is present and diagnose it regardless of
warn_return_type.
* g++.dg/cpp1y/constexpr-96182.C: New test.
* g++.dg/other/error35.C (S<T>::g()): Add return statement.
* g++.dg/cpp1y/pr63996.C (foo): Likewise.
* g++.dg/cpp1y/constexpr-return2.C (f): Likewise.
* g++.dg/cpp1y/var-templ44.C (make_array): Add throw 1.
--- gcc/cp/decl.c.jj 2020-07-13 19:09:27.258953908 +0200
+++ gcc/cp/decl.c 2020-07-13 22:25:42.437062842 +0200
@@ -17164,7 +17164,10 @@ finish_function (bool inline_p)
BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
/* Complain if there's just no return statement. */
- if (warn_return_type
+ if ((warn_return_type
+ || (cxx_dialect >= cxx14
+ && DECL_DECLARED_CONSTEXPR_P (fndecl)
+ && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl))))
&& !VOID_TYPE_P (TREE_TYPE (fntype))
&& !dependent_type_p (TREE_TYPE (fntype))
&& !current_function_returns_value && !current_function_returns_null
@@ -17196,8 +17199,14 @@ finish_function (bool inline_p)
global_dc->option_state))
add_return_star_this_fixit (&richloc, fndecl);
}
- if (warning_at (&richloc, OPT_Wreturn_type,
- "no return statement in function returning non-void"))
+ if (cxx_dialect >= cxx14
+ && DECL_DECLARED_CONSTEXPR_P (fndecl)
+ && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
+ error_at (&richloc, "no return statement in %<constexpr%> function "
+ "returning non-void");
+ else if (warning_at (&richloc, OPT_Wreturn_type,
+ "no return statement in function returning "
+ "non-void"))
TREE_NO_WARNING (fndecl) = 1;
}
--- gcc/testsuite/g++.dg/other/error35.C.jj 2020-01-12 11:54:37.214401324 +0100
+++ gcc/testsuite/g++.dg/other/error35.C 2020-07-13 22:35:55.359228614 +0200
@@ -9,6 +9,6 @@ template <typename> struct S {
enum S<char>::E;
template <typename T> enum S<T>::E : int { b };
template <typename T>
-constexpr int S<T>::g() const { b; } // { dg-error "not declared" }
+constexpr int S<T>::g() const { b; if (false) return 0; } // { dg-error "not declared" }
static_assert(S<char>().g() == 1, ""); // { dg-error "" }
// { dg-message "in .constexpr. expansion of" "" { target *-*-* } .-1 }
--- gcc/testsuite/g++.dg/cpp1y/pr63996.C.jj 2020-01-12 11:54:37.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/pr63996.C 2020-07-13 22:17:39.034004329 +0200
@@ -5,6 +5,7 @@ constexpr int
foo (int i)
{
int a[i] = { }; // { dg-error "7:ISO C\\+\\+ forbids variable length array .a" }
+ if (i == 23) return 0;
}
constexpr int j = foo (1); // { dg-error "flows off the end|in .constexpr. expansion of" }
--- gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C.jj 2020-07-13 19:16:42.742936492 +0200
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C 2020-07-13 19:16:12.264357640 +0200
@@ -0,0 +1,6 @@
+// PR c++/96182
+// { dg-do compile { target c++11 } }
+
+constexpr int foo () {} // { dg-error "no return statement in 'constexpr' function returning non-void" "" { target c++14 } }
+// { dg-error "body of 'constexpr' function 'constexpr int foo\\\(\\\)' not a return-statement" "" { target c++11_only } .-1 }
+// { dg-warning "no return statement in function returning non-void" "" { target c++11_only } .-2 }
--- gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C.jj 2020-01-12 11:54:37.115402818 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C 2020-07-13 22:17:03.582513397 +0200
@@ -3,6 +3,7 @@
constexpr int f (int i)
{
+ if (i == -1) return 0;
}
constexpr int i = f(42); // { dg-error "flows off the end|in .constexpr. expansion of " }
--- gcc/testsuite/g++.dg/cpp1y/var-templ44.C.jj 2020-01-12 11:54:37.123402697 +0100
+++ gcc/testsuite/g++.dg/cpp1y/var-templ44.C 2020-07-13 22:35:03.322980157 +0200
@@ -26,5 +26,6 @@ constexpr auto make_array()
-> array<conditional_t<is_void_v<_Dest>, common_type_t<>, _Dest>,
sizeof...(_Types)> {
static_assert(__or_<__not_<is_void<_Dest>>, __and_<>>::value, ""); // { dg-error "static assert" }
+ throw 1;
}
auto d = make_array();
Jakub
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182]
2020-07-14 8:50 [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182] Jakub Jelinek
@ 2020-07-29 19:30 ` Jason Merrill
2020-07-31 7:52 ` Jakub Jelinek
0 siblings, 1 reply; 4+ messages in thread
From: Jason Merrill @ 2020-07-29 19:30 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 7/14/20 4:50 AM, Jakub Jelinek wrote:
> Hi!
>
> For C++11 we already emit an error if a constexpr function doesn't contain
> a return statement, because in C++11 that is the only thing it needs to
> contain, but for C++14 we would normally issue a -Wreturn-type warning.
>
> As mentioned by Jonathan, such constexpr functions are invalid, no
> diagnostics required, because there doesn't exist any arguments for
> which it would result in valid constant expression.
>
> This raises it to an error in such cases. The !LAMBDA_TYPE_P case
> is to avoid error on g++.dg/pr81194.C where the user didn't write
> constexpr anywhere and the operator() is compiler generated.
We set DECL_DECLARED_CONSTEXPR_P on lambdas earlier in finish_function
if suitable; can we move this diagnostic up before that?
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2020-07-14 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/96182
> * decl.c (finish_function): In constexpr functions other than
> lambdas use for C++14 and later error instead of warning if no
> return statement is present and diagnose it regardless of
> warn_return_type.
>
> * g++.dg/cpp1y/constexpr-96182.C: New test.
> * g++.dg/other/error35.C (S<T>::g()): Add return statement.
> * g++.dg/cpp1y/pr63996.C (foo): Likewise.
> * g++.dg/cpp1y/constexpr-return2.C (f): Likewise.
> * g++.dg/cpp1y/var-templ44.C (make_array): Add throw 1.
>
> --- gcc/cp/decl.c.jj 2020-07-13 19:09:27.258953908 +0200
> +++ gcc/cp/decl.c 2020-07-13 22:25:42.437062842 +0200
> @@ -17164,7 +17164,10 @@ finish_function (bool inline_p)
> BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
>
> /* Complain if there's just no return statement. */
> - if (warn_return_type
> + if ((warn_return_type
> + || (cxx_dialect >= cxx14
> + && DECL_DECLARED_CONSTEXPR_P (fndecl)
> + && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl))))
> && !VOID_TYPE_P (TREE_TYPE (fntype))
> && !dependent_type_p (TREE_TYPE (fntype))
> && !current_function_returns_value && !current_function_returns_null
> @@ -17196,8 +17199,14 @@ finish_function (bool inline_p)
> global_dc->option_state))
> add_return_star_this_fixit (&richloc, fndecl);
> }
> - if (warning_at (&richloc, OPT_Wreturn_type,
> - "no return statement in function returning non-void"))
> + if (cxx_dialect >= cxx14
> + && DECL_DECLARED_CONSTEXPR_P (fndecl)
> + && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
> + error_at (&richloc, "no return statement in %<constexpr%> function "
> + "returning non-void");
> + else if (warning_at (&richloc, OPT_Wreturn_type,
> + "no return statement in function returning "
> + "non-void"))
> TREE_NO_WARNING (fndecl) = 1;
> }
>
> --- gcc/testsuite/g++.dg/other/error35.C.jj 2020-01-12 11:54:37.214401324 +0100
> +++ gcc/testsuite/g++.dg/other/error35.C 2020-07-13 22:35:55.359228614 +0200
> @@ -9,6 +9,6 @@ template <typename> struct S {
> enum S<char>::E;
> template <typename T> enum S<T>::E : int { b };
> template <typename T>
> -constexpr int S<T>::g() const { b; } // { dg-error "not declared" }
> +constexpr int S<T>::g() const { b; if (false) return 0; } // { dg-error "not declared" }
> static_assert(S<char>().g() == 1, ""); // { dg-error "" }
> // { dg-message "in .constexpr. expansion of" "" { target *-*-* } .-1 }
> --- gcc/testsuite/g++.dg/cpp1y/pr63996.C.jj 2020-01-12 11:54:37.000000000 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/pr63996.C 2020-07-13 22:17:39.034004329 +0200
> @@ -5,6 +5,7 @@ constexpr int
> foo (int i)
> {
> int a[i] = { }; // { dg-error "7:ISO C\\+\\+ forbids variable length array .a" }
> + if (i == 23) return 0;
> }
>
> constexpr int j = foo (1); // { dg-error "flows off the end|in .constexpr. expansion of" }
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C.jj 2020-07-13 19:16:42.742936492 +0200
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C 2020-07-13 19:16:12.264357640 +0200
> @@ -0,0 +1,6 @@
> +// PR c++/96182
> +// { dg-do compile { target c++11 } }
> +
> +constexpr int foo () {} // { dg-error "no return statement in 'constexpr' function returning non-void" "" { target c++14 } }
> +// { dg-error "body of 'constexpr' function 'constexpr int foo\\\(\\\)' not a return-statement" "" { target c++11_only } .-1 }
> +// { dg-warning "no return statement in function returning non-void" "" { target c++11_only } .-2 }
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C.jj 2020-01-12 11:54:37.115402818 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C 2020-07-13 22:17:03.582513397 +0200
> @@ -3,6 +3,7 @@
>
> constexpr int f (int i)
> {
> + if (i == -1) return 0;
> }
>
> constexpr int i = f(42); // { dg-error "flows off the end|in .constexpr. expansion of " }
> --- gcc/testsuite/g++.dg/cpp1y/var-templ44.C.jj 2020-01-12 11:54:37.123402697 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/var-templ44.C 2020-07-13 22:35:03.322980157 +0200
> @@ -26,5 +26,6 @@ constexpr auto make_array()
> -> array<conditional_t<is_void_v<_Dest>, common_type_t<>, _Dest>,
> sizeof...(_Types)> {
> static_assert(__or_<__not_<is_void<_Dest>>, __and_<>>::value, ""); // { dg-error "static assert" }
> + throw 1;
> }
> auto d = make_array();
>
> Jakub
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182]
2020-07-29 19:30 ` Jason Merrill
@ 2020-07-31 7:52 ` Jakub Jelinek
2020-07-31 20:28 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Jakub Jelinek @ 2020-07-31 7:52 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
On Wed, Jul 29, 2020 at 03:30:07PM -0400, Jason Merrill via Gcc-patches wrote:
> On 7/14/20 4:50 AM, Jakub Jelinek wrote:
> > For C++11 we already emit an error if a constexpr function doesn't contain
> > a return statement, because in C++11 that is the only thing it needs to
> > contain, but for C++14 we would normally issue a -Wreturn-type warning.
> >
> > As mentioned by Jonathan, such constexpr functions are invalid, no
> > diagnostics required, because there doesn't exist any arguments for
> > which it would result in valid constant expression.
> >
> > This raises it to an error in such cases. The !LAMBDA_TYPE_P case
> > is to avoid error on g++.dg/pr81194.C where the user didn't write
> > constexpr anywhere and the operator() is compiler generated.
>
> We set DECL_DECLARED_CONSTEXPR_P on lambdas earlier in finish_function if
> suitable; can we move this diagnostic up before that?
That works too. Bootstrapped/regtested on x86_64-linux and i686-linux, ok
for trunk then?
2020-07-31 Jakub Jelinek <jakub@redhat.com>
PR c++/96182
* decl.c (finish_function): In constexpr functions use for C++14 and
later error instead of warning if no return statement is present and
diagnose it regardless of warn_return_type. Move the warn_return_type
diagnostics earlier in the function.
* g++.dg/cpp1y/constexpr-96182.C: New test.
* g++.dg/other/error35.C (S<T>::g()): Add return statement.
* g++.dg/cpp1y/pr63996.C (foo): Likewise.
* g++.dg/cpp1y/constexpr-return2.C (f): Likewise.
* g++.dg/cpp1y/var-templ44.C (make_array): Add throw 1.
--- gcc/cp/decl.c.jj 2020-07-29 11:57:23.340517489 +0200
+++ gcc/cp/decl.c 2020-07-30 20:44:33.634951396 +0200
@@ -17112,6 +17112,51 @@ finish_function (bool inline_p)
DECL_ATTRIBUTES (fndecl)))
omp_declare_variant_finalize (fndecl, attr);
+ /* Complain if there's just no return statement. */
+ if ((warn_return_type
+ || (cxx_dialect >= cxx14
+ && DECL_DECLARED_CONSTEXPR_P (fndecl)))
+ && !VOID_TYPE_P (TREE_TYPE (fntype))
+ && !dependent_type_p (TREE_TYPE (fntype))
+ && !current_function_returns_value && !current_function_returns_null
+ /* Don't complain if we abort or throw. */
+ && !current_function_returns_abnormally
+ /* Don't complain if there's an infinite loop. */
+ && !current_function_infinite_loop
+ /* Don't complain if we are declared noreturn. */
+ && !TREE_THIS_VOLATILE (fndecl)
+ && !DECL_NAME (DECL_RESULT (fndecl))
+ && !TREE_NO_WARNING (fndecl)
+ /* Structor return values (if any) are set by the compiler. */
+ && !DECL_CONSTRUCTOR_P (fndecl)
+ && !DECL_DESTRUCTOR_P (fndecl)
+ && targetm.warn_func_return (fndecl))
+ {
+ gcc_rich_location richloc (input_location);
+ /* Potentially add a "return *this;" fix-it hint for
+ assignment operators. */
+ if (IDENTIFIER_ASSIGN_OP_P (DECL_NAME (fndecl)))
+ {
+ tree valtype = TREE_TYPE (DECL_RESULT (fndecl));
+ if (TREE_CODE (valtype) == REFERENCE_TYPE
+ && current_class_ref
+ && same_type_ignoring_top_level_qualifiers_p
+ (TREE_TYPE (valtype), TREE_TYPE (current_class_ref))
+ && global_dc->option_enabled (OPT_Wreturn_type,
+ global_dc->lang_mask,
+ global_dc->option_state))
+ add_return_star_this_fixit (&richloc, fndecl);
+ }
+ if (cxx_dialect >= cxx14
+ && DECL_DECLARED_CONSTEXPR_P (fndecl))
+ error_at (&richloc, "no return statement in %<constexpr%> function "
+ "returning non-void");
+ else if (warning_at (&richloc, OPT_Wreturn_type,
+ "no return statement in function returning "
+ "non-void"))
+ TREE_NO_WARNING (fndecl) = 1;
+ }
+
/* Lambda closure members are implicitly constexpr if possible. */
if (cxx_dialect >= cxx17
&& LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
@@ -17163,44 +17208,6 @@ finish_function (bool inline_p)
to the FUNCTION_DECL node itself. */
BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
- /* Complain if there's just no return statement. */
- if (warn_return_type
- && !VOID_TYPE_P (TREE_TYPE (fntype))
- && !dependent_type_p (TREE_TYPE (fntype))
- && !current_function_returns_value && !current_function_returns_null
- /* Don't complain if we abort or throw. */
- && !current_function_returns_abnormally
- /* Don't complain if there's an infinite loop. */
- && !current_function_infinite_loop
- /* Don't complain if we are declared noreturn. */
- && !TREE_THIS_VOLATILE (fndecl)
- && !DECL_NAME (DECL_RESULT (fndecl))
- && !TREE_NO_WARNING (fndecl)
- /* Structor return values (if any) are set by the compiler. */
- && !DECL_CONSTRUCTOR_P (fndecl)
- && !DECL_DESTRUCTOR_P (fndecl)
- && targetm.warn_func_return (fndecl))
- {
- gcc_rich_location richloc (input_location);
- /* Potentially add a "return *this;" fix-it hint for
- assignment operators. */
- if (IDENTIFIER_ASSIGN_OP_P (DECL_NAME (fndecl)))
- {
- tree valtype = TREE_TYPE (DECL_RESULT (fndecl));
- if (TREE_CODE (valtype) == REFERENCE_TYPE
- && current_class_ref
- && same_type_ignoring_top_level_qualifiers_p
- (TREE_TYPE (valtype), TREE_TYPE (current_class_ref))
- && global_dc->option_enabled (OPT_Wreturn_type,
- global_dc->lang_mask,
- global_dc->option_state))
- add_return_star_this_fixit (&richloc, fndecl);
- }
- if (warning_at (&richloc, OPT_Wreturn_type,
- "no return statement in function returning non-void"))
- TREE_NO_WARNING (fndecl) = 1;
- }
-
/* Store the end of the function, so that we get good line number
info for the epilogue. */
cfun->function_end_locus = input_location;
--- gcc/testsuite/g++.dg/other/error35.C.jj 2020-01-12 11:54:37.214401324 +0100
+++ gcc/testsuite/g++.dg/other/error35.C 2020-07-13 22:35:55.359228614 +0200
@@ -9,6 +9,6 @@ template <typename> struct S {
enum S<char>::E;
template <typename T> enum S<T>::E : int { b };
template <typename T>
-constexpr int S<T>::g() const { b; } // { dg-error "not declared" }
+constexpr int S<T>::g() const { b; if (false) return 0; } // { dg-error "not declared" }
static_assert(S<char>().g() == 1, ""); // { dg-error "" }
// { dg-message "in .constexpr. expansion of" "" { target *-*-* } .-1 }
--- gcc/testsuite/g++.dg/cpp1y/pr63996.C.jj 2020-01-12 11:54:37.000000000 +0100
+++ gcc/testsuite/g++.dg/cpp1y/pr63996.C 2020-07-13 22:17:39.034004329 +0200
@@ -5,6 +5,7 @@ constexpr int
foo (int i)
{
int a[i] = { }; // { dg-error "7:ISO C\\+\\+ forbids variable length array .a" }
+ if (i == 23) return 0;
}
constexpr int j = foo (1); // { dg-error "flows off the end|in .constexpr. expansion of" }
--- gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C.jj 2020-07-13 19:16:42.742936492 +0200
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C 2020-07-13 19:16:12.264357640 +0200
@@ -0,0 +1,6 @@
+// PR c++/96182
+// { dg-do compile { target c++11 } }
+
+constexpr int foo () {} // { dg-error "no return statement in 'constexpr' function returning non-void" "" { target c++14 } }
+// { dg-error "body of 'constexpr' function 'constexpr int foo\\\(\\\)' not a return-statement" "" { target c++11_only } .-1 }
+// { dg-warning "no return statement in function returning non-void" "" { target c++11_only } .-2 }
--- gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C.jj 2020-01-12 11:54:37.115402818 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C 2020-07-13 22:17:03.582513397 +0200
@@ -3,6 +3,7 @@
constexpr int f (int i)
{
+ if (i == -1) return 0;
}
constexpr int i = f(42); // { dg-error "flows off the end|in .constexpr. expansion of " }
--- gcc/testsuite/g++.dg/cpp1y/var-templ44.C.jj 2020-01-12 11:54:37.123402697 +0100
+++ gcc/testsuite/g++.dg/cpp1y/var-templ44.C 2020-07-13 22:35:03.322980157 +0200
@@ -26,5 +26,6 @@ constexpr auto make_array()
-> array<conditional_t<is_void_v<_Dest>, common_type_t<>, _Dest>,
sizeof...(_Types)> {
static_assert(__or_<__not_<is_void<_Dest>>, __and_<>>::value, ""); // { dg-error "static assert" }
+ throw 1;
}
auto d = make_array();
Jakub
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182]
2020-07-31 7:52 ` Jakub Jelinek
@ 2020-07-31 20:28 ` Jason Merrill
0 siblings, 0 replies; 4+ messages in thread
From: Jason Merrill @ 2020-07-31 20:28 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 7/31/20 3:52 AM, Jakub Jelinek wrote:
> On Wed, Jul 29, 2020 at 03:30:07PM -0400, Jason Merrill via Gcc-patches wrote:
>> On 7/14/20 4:50 AM, Jakub Jelinek wrote:
>>> For C++11 we already emit an error if a constexpr function doesn't contain
>>> a return statement, because in C++11 that is the only thing it needs to
>>> contain, but for C++14 we would normally issue a -Wreturn-type warning.
>>>
>>> As mentioned by Jonathan, such constexpr functions are invalid, no
>>> diagnostics required, because there doesn't exist any arguments for
>>> which it would result in valid constant expression.
>>>
>>> This raises it to an error in such cases. The !LAMBDA_TYPE_P case
>>> is to avoid error on g++.dg/pr81194.C where the user didn't write
>>> constexpr anywhere and the operator() is compiler generated.
>>
>> We set DECL_DECLARED_CONSTEXPR_P on lambdas earlier in finish_function if
>> suitable; can we move this diagnostic up before that?
>
> That works too. Bootstrapped/regtested on x86_64-linux and i686-linux, ok
> for trunk then?
OK.
> 2020-07-31 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/96182
> * decl.c (finish_function): In constexpr functions use for C++14 and
> later error instead of warning if no return statement is present and
> diagnose it regardless of warn_return_type. Move the warn_return_type
> diagnostics earlier in the function.
>
> * g++.dg/cpp1y/constexpr-96182.C: New test.
> * g++.dg/other/error35.C (S<T>::g()): Add return statement.
> * g++.dg/cpp1y/pr63996.C (foo): Likewise.
> * g++.dg/cpp1y/constexpr-return2.C (f): Likewise.
> * g++.dg/cpp1y/var-templ44.C (make_array): Add throw 1.
>
> --- gcc/cp/decl.c.jj 2020-07-29 11:57:23.340517489 +0200
> +++ gcc/cp/decl.c 2020-07-30 20:44:33.634951396 +0200
> @@ -17112,6 +17112,51 @@ finish_function (bool inline_p)
> DECL_ATTRIBUTES (fndecl)))
> omp_declare_variant_finalize (fndecl, attr);
>
> + /* Complain if there's just no return statement. */
> + if ((warn_return_type
> + || (cxx_dialect >= cxx14
> + && DECL_DECLARED_CONSTEXPR_P (fndecl)))
> + && !VOID_TYPE_P (TREE_TYPE (fntype))
> + && !dependent_type_p (TREE_TYPE (fntype))
> + && !current_function_returns_value && !current_function_returns_null
> + /* Don't complain if we abort or throw. */
> + && !current_function_returns_abnormally
> + /* Don't complain if there's an infinite loop. */
> + && !current_function_infinite_loop
> + /* Don't complain if we are declared noreturn. */
> + && !TREE_THIS_VOLATILE (fndecl)
> + && !DECL_NAME (DECL_RESULT (fndecl))
> + && !TREE_NO_WARNING (fndecl)
> + /* Structor return values (if any) are set by the compiler. */
> + && !DECL_CONSTRUCTOR_P (fndecl)
> + && !DECL_DESTRUCTOR_P (fndecl)
> + && targetm.warn_func_return (fndecl))
> + {
> + gcc_rich_location richloc (input_location);
> + /* Potentially add a "return *this;" fix-it hint for
> + assignment operators. */
> + if (IDENTIFIER_ASSIGN_OP_P (DECL_NAME (fndecl)))
> + {
> + tree valtype = TREE_TYPE (DECL_RESULT (fndecl));
> + if (TREE_CODE (valtype) == REFERENCE_TYPE
> + && current_class_ref
> + && same_type_ignoring_top_level_qualifiers_p
> + (TREE_TYPE (valtype), TREE_TYPE (current_class_ref))
> + && global_dc->option_enabled (OPT_Wreturn_type,
> + global_dc->lang_mask,
> + global_dc->option_state))
> + add_return_star_this_fixit (&richloc, fndecl);
> + }
> + if (cxx_dialect >= cxx14
> + && DECL_DECLARED_CONSTEXPR_P (fndecl))
> + error_at (&richloc, "no return statement in %<constexpr%> function "
> + "returning non-void");
> + else if (warning_at (&richloc, OPT_Wreturn_type,
> + "no return statement in function returning "
> + "non-void"))
> + TREE_NO_WARNING (fndecl) = 1;
> + }
> +
> /* Lambda closure members are implicitly constexpr if possible. */
> if (cxx_dialect >= cxx17
> && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
> @@ -17163,44 +17208,6 @@ finish_function (bool inline_p)
> to the FUNCTION_DECL node itself. */
> BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
>
> - /* Complain if there's just no return statement. */
> - if (warn_return_type
> - && !VOID_TYPE_P (TREE_TYPE (fntype))
> - && !dependent_type_p (TREE_TYPE (fntype))
> - && !current_function_returns_value && !current_function_returns_null
> - /* Don't complain if we abort or throw. */
> - && !current_function_returns_abnormally
> - /* Don't complain if there's an infinite loop. */
> - && !current_function_infinite_loop
> - /* Don't complain if we are declared noreturn. */
> - && !TREE_THIS_VOLATILE (fndecl)
> - && !DECL_NAME (DECL_RESULT (fndecl))
> - && !TREE_NO_WARNING (fndecl)
> - /* Structor return values (if any) are set by the compiler. */
> - && !DECL_CONSTRUCTOR_P (fndecl)
> - && !DECL_DESTRUCTOR_P (fndecl)
> - && targetm.warn_func_return (fndecl))
> - {
> - gcc_rich_location richloc (input_location);
> - /* Potentially add a "return *this;" fix-it hint for
> - assignment operators. */
> - if (IDENTIFIER_ASSIGN_OP_P (DECL_NAME (fndecl)))
> - {
> - tree valtype = TREE_TYPE (DECL_RESULT (fndecl));
> - if (TREE_CODE (valtype) == REFERENCE_TYPE
> - && current_class_ref
> - && same_type_ignoring_top_level_qualifiers_p
> - (TREE_TYPE (valtype), TREE_TYPE (current_class_ref))
> - && global_dc->option_enabled (OPT_Wreturn_type,
> - global_dc->lang_mask,
> - global_dc->option_state))
> - add_return_star_this_fixit (&richloc, fndecl);
> - }
> - if (warning_at (&richloc, OPT_Wreturn_type,
> - "no return statement in function returning non-void"))
> - TREE_NO_WARNING (fndecl) = 1;
> - }
> -
> /* Store the end of the function, so that we get good line number
> info for the epilogue. */
> cfun->function_end_locus = input_location;
> --- gcc/testsuite/g++.dg/other/error35.C.jj 2020-01-12 11:54:37.214401324 +0100
> +++ gcc/testsuite/g++.dg/other/error35.C 2020-07-13 22:35:55.359228614 +0200
> @@ -9,6 +9,6 @@ template <typename> struct S {
> enum S<char>::E;
> template <typename T> enum S<T>::E : int { b };
> template <typename T>
> -constexpr int S<T>::g() const { b; } // { dg-error "not declared" }
> +constexpr int S<T>::g() const { b; if (false) return 0; } // { dg-error "not declared" }
> static_assert(S<char>().g() == 1, ""); // { dg-error "" }
> // { dg-message "in .constexpr. expansion of" "" { target *-*-* } .-1 }
> --- gcc/testsuite/g++.dg/cpp1y/pr63996.C.jj 2020-01-12 11:54:37.000000000 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/pr63996.C 2020-07-13 22:17:39.034004329 +0200
> @@ -5,6 +5,7 @@ constexpr int
> foo (int i)
> {
> int a[i] = { }; // { dg-error "7:ISO C\\+\\+ forbids variable length array .a" }
> + if (i == 23) return 0;
> }
>
> constexpr int j = foo (1); // { dg-error "flows off the end|in .constexpr. expansion of" }
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C.jj 2020-07-13 19:16:42.742936492 +0200
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-96182.C 2020-07-13 19:16:12.264357640 +0200
> @@ -0,0 +1,6 @@
> +// PR c++/96182
> +// { dg-do compile { target c++11 } }
> +
> +constexpr int foo () {} // { dg-error "no return statement in 'constexpr' function returning non-void" "" { target c++14 } }
> +// { dg-error "body of 'constexpr' function 'constexpr int foo\\\(\\\)' not a return-statement" "" { target c++11_only } .-1 }
> +// { dg-warning "no return statement in function returning non-void" "" { target c++11_only } .-2 }
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C.jj 2020-01-12 11:54:37.115402818 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C 2020-07-13 22:17:03.582513397 +0200
> @@ -3,6 +3,7 @@
>
> constexpr int f (int i)
> {
> + if (i == -1) return 0;
> }
>
> constexpr int i = f(42); // { dg-error "flows off the end|in .constexpr. expansion of " }
> --- gcc/testsuite/g++.dg/cpp1y/var-templ44.C.jj 2020-01-12 11:54:37.123402697 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/var-templ44.C 2020-07-13 22:35:03.322980157 +0200
> @@ -26,5 +26,6 @@ constexpr auto make_array()
> -> array<conditional_t<is_void_v<_Dest>, common_type_t<>, _Dest>,
> sizeof...(_Types)> {
> static_assert(__or_<__not_<is_void<_Dest>>, __and_<>>::value, ""); // { dg-error "static assert" }
> + throw 1;
> }
> auto d = make_array();
>
>
> Jakub
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-07-31 20:28 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-07-14 8:50 [PATCH] c++: Use error_at rather than warning_at for missing return in constexpr functions [PR96182] Jakub Jelinek
2020-07-29 19:30 ` Jason Merrill
2020-07-31 7:52 ` Jakub Jelinek
2020-07-31 20:28 ` Jason Merrill
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