Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
We were silently accepting the pr65923.C specialization of std::swap with
the wrong exception specification; it should be declared noexcept. Let's
limit ignoring mismatch with system headers to extern "C" functions so we
get a diagnostic for the C++ library.
In the case of an omitted exception-specification, let's also lower the
error to a pedwarn, and copy the missing spec over, to avoid a hard break
for code that accidentally relied on the old behavior.
...except extern "C" functions keep the new spec, to avoid breaking dubious
code like noexcept-type19.C.
gcc/cp/ChangeLog:
* decl.cc (check_redeclaration_exception_specification): Remove
OPT_Wsystem_headers from pedwarn when the old declaration is
in a system header. Also check std namespace.
gcc/testsuite/ChangeLog:
* g++.dg/diagnostic/pr65923.C: Add noexcept.
* g++.dg/cpp1z/aligned-new3.C: Expect pedwarn.
* g++.dg/cpp1z/noexcept-type19.C: Add comment.
---
gcc/cp/decl.cc | 20 ++++++++++++++++++--
gcc/testsuite/g++.dg/cpp1z/aligned-new3.C | 3 ++-
gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C | 2 +-
gcc/testsuite/g++.dg/diagnostic/pr65923.C | 2 +-
4 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index f0271308d92..2190ede745b 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1395,17 +1395,33 @@ check_redeclaration_exception_specification (tree
new_decl,
bool complained = true;
location_t new_loc = DECL_SOURCE_LOCATION (new_decl);
auto_diagnostic_group d;
- if (DECL_IN_SYSTEM_HEADER (old_decl))
+
+ if (DECL_IN_SYSTEM_HEADER (old_decl) && DECL_EXTERN_C_P (old_decl))
+ /* Don't fuss about the C library; the C library functions are not
+ specified to have exception specifications (just behave as if they
+ have them), but some implementations include them. */
complained = pedwarn (new_loc, OPT_Wsystem_headers, msg, new_decl);
else if (!flag_exceptions)
/* We used to silently permit mismatched eh specs with
- -fno-exceptions, so make them a pedwarn now. */
+ -fno-exceptions, so only complain if -pedantic. */
complained = pedwarn (new_loc, OPT_Wpedantic, msg, new_decl);
+ else if (!new_exceptions)
+ /* Reduce to pedwarn for omitted exception specification. No warning
+ flag for this; silence the warning by correcting the code. */
+ complained = pedwarn (new_loc, 0, msg, new_decl);
else
error_at (new_loc, msg, new_decl);
+
if (complained)
inform (DECL_SOURCE_LOCATION (old_decl),
"from previous declaration %qF", old_decl);
+
+ /* Copy the old exception specification if new_decl has none. Unless the
+ old decl is extern "C", as obscure code might depend on the type of
+ the new declaration (e.g. noexcept-type19.C). */
+ if (!new_exceptions && !DECL_EXTERN_C_P (old_decl))
+ TREE_TYPE (new_decl)
+ = build_exception_variant (TREE_TYPE (new_decl), old_exceptions);
}
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/aligned-new3.C
b/gcc/testsuite/g++.dg/cpp1z/aligned-new3.C
index 08cd732ac7b..165c3771ab9 100644
--- a/gcc/testsuite/g++.dg/cpp1z/aligned-new3.C
+++ b/gcc/testsuite/g++.dg/cpp1z/aligned-new3.C
@@ -1,4 +1,5 @@
// { dg-do run { target c++17 } }
+// { dg-options "" }
#include <new>
@@ -12,7 +13,7 @@ void* operator new (std::size_t n, std::align_val_t)
}
bool deleted = false;
-void operator delete (void *p, std::size_t, std::align_val_t)
+void operator delete (void *p, std::size_t, std::align_val_t) // { dg-warning
"exception specifier" }
{
deleted = true;
operator delete (p);
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
index 571c426aa67..9beadd08298 100644
--- a/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
@@ -2,7 +2,7 @@
#include "noexcept-type19.h"
-extern "C" void *malloc (size_t);
+extern "C" void *malloc (size_t); // silently discard throw() from system
header
template<class T> void f(T*);
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr65923.C
b/gcc/testsuite/g++.dg/diagnostic/pr65923.C
index 036f4478181..40b6b5965fa 100644
--- a/gcc/testsuite/g++.dg/diagnostic/pr65923.C
+++ b/gcc/testsuite/g++.dg/diagnostic/pr65923.C
@@ -16,7 +16,7 @@ struct X2
namespace std
{
- template<> void swap(X&, X&)
+ template<> void swap(X&, X&) noexcept
{
constexpr std::chrono::duration<long double> operator""s(long double);
}
base-commit: 69d82c1dccb3583464228eb5449e29918eeb4ee4
--
2.46.0
