From 1d87302a8e20c1f49dd37177ec869ee94abc11a5 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Tue, 3 Nov 2020 17:46:23 -0500
Subject: [PATCH] c++: Add -Wexceptions warning option [PR97675]
This PR asks that we add a warning option for an existing (very old)
warning, so that it can be disabled selectively. clang++ uses
-Wexceptions for this, so I added this new option rather than using
e.g. -Wnoexcept.
gcc/c-family/ChangeLog:
PR c++/97675
* c.opt (Wexceptions): New option.
gcc/cp/ChangeLog:
PR c++/97675
* except.c (check_handlers_1): Use OPT_Wexceptions for the
warning. Use inform for the second part of the warning.
gcc/ChangeLog:
PR c++/97675
* doc/invoke.texi: Document -Wexceptions.
gcc/testsuite/ChangeLog:
PR c++/97675
* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
* g++.dg/warn/Wexceptions1.C: New test.
* g++.dg/warn/Wexceptions2.C: New test.
---
gcc/c-family/c.opt | 4 ++++
gcc/cp/except.c | 9 ++++-----
gcc/doc/invoke.texi | 8 +++++++-
gcc/testsuite/g++.dg/warn/Wexceptions1.C | 9 +++++++++
gcc/testsuite/g++.dg/warn/Wexceptions2.C | 10 ++++++++++
gcc/testsuite/g++.old-deja/g++.eh/catch10.C | 4 ++--
6 files changed, 36 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions1.C
create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions2.C
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 5bfe3a68f66b..ebd07cc80595 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -579,6 +579,10 @@ Werror-implicit-function-declaration
C ObjC RejectNegative Warning Alias(Werror=, implicit-function-declaration)
This switch is deprecated; use -Werror=implicit-function-declaration instead.
+Wexceptions
+C++ ObjC++ Var(warn_exceptions) Init(1)
+Warn when an exception handler is shadowed by another handler.
+
Wextra
C ObjC C++ ObjC++ Warning
; in common.opt
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index cb1a4105dae1..985206f6a649 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -975,11 +975,10 @@ check_handlers_1 (tree master, tree_stmt_iterator i)
tree handler = tsi_stmt (i);
if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
{
- warning_at (EXPR_LOCATION (handler), 0,
- "exception of type %qT will be caught",
- TREE_TYPE (handler));
- warning_at (EXPR_LOCATION (master), 0,
- " by earlier handler for %qT", type);
+ if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
+ "exception of type %qT will be caught by earlier "
+ "handler", TREE_TYPE (handler)))
+ inform (EXPR_LOCATION (master), "for type %qT", type);
break;
}
}
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 812fa46e9067..32f90ef20229 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -240,7 +240,7 @@ in the following sections.
-Wctor-dtor-privacy -Wno-delete-incomplete @gol
-Wdelete-non-virtual-dtor -Wdeprecated-copy -Wdeprecated-copy-dtor @gol
-Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
--Weffc++ -Wextra-semi -Wno-inaccessible-base @gol
+-Weffc++ -Wno-exceptions -Wextra-semi -Wno-inaccessible-base @gol
-Wno-inherited-variadic-ctor -Wno-init-list-lifetime @gol
-Wno-invalid-offsetof -Wno-literal-suffix -Wmismatched-tags @gol
-Wmultiple-inheritance -Wnamespaces -Wnarrowing @gol
@@ -3739,6 +3739,12 @@ When selecting this option, be aware that the standard library
headers do not obey all of these guidelines; use @samp{grep -v}
to filter out those warnings.
+@item -Wno-exceptions @r{(C++ and Objective-C++ only)}
+@opindex Wexceptions
+@opindex Wno-exceptions
+Disable the warning about the case when an exception handler is shadowed by
+another handler, which can point out a wrong ordering of exception handlers.
+
@item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
@opindex Wstrict-null-sentinel
@opindex Wno-strict-null-sentinel
diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions1.C b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
new file mode 100644
index 000000000000..af140fd0dc2c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
@@ -0,0 +1,9 @@
+// PR c++/97675
+
+struct Base { };
+struct Child : Base { };
+int main() {
+ try { throw Child(); }
+ catch (Base const&) { }
+ catch (Child const&) { } // { dg-warning "exception of type .Child. will be caught by earlier handler" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions2.C b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
new file mode 100644
index 000000000000..07c5155ac06e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
@@ -0,0 +1,10 @@
+// PR c++/97675
+// { dg-additional-options -Wno-exceptions }
+
+struct Base { };
+struct Child : Base { };
+int main() {
+ try { throw Child(); }
+ catch (Base const&) { }
+ catch (Child const&) { } // { dg-bogus "exception of type .Child. will be caught by earlier handler" }
+}
diff --git a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
index 2300a9461870..7cc609645a23 100644
--- a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
+++ b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
@@ -13,8 +13,8 @@ void g()
catch (A*) { }
try { f(); }
- catch (A*) { } // { dg-warning "" } A* before B*
- catch (B*) { } // { dg-warning "" } A* before B*
+ catch (A*) { } // { dg-message "for type" } A* before B*
+ catch (B*) { } // { dg-warning "will be caught" } A* before B*
try { f(); }
catch (A*) { }
--
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