On 24 May, Jason Merrill wrote:
> On Mon, May 15, 2017 at 3:58 PM, Martin Sebor <mse...@gmail.com> wrote:
>>> So how about the following then? I stayed with the catch part and added
>>> a parameter to the warning to let the user decide on the warnings she/he
>>> wants to get: -Wcatch-value=n.
>>> -Wcatch-value=1 only warns for polymorphic classes that are caught by
>>> value (to avoid slicing), -Wcatch-value=2 warns for all classes that
>>> are caught by value (to avoid copies). And finally -Wcatch-value=3
>>> warns for everything not caught by reference to find typos (like pointer
>>> instead of reference) and bad coding practices.
>>
>> It seems reasonable to me. I'm not too fond of multi-level
>> warnings since few users take advantage of anything but the
>> default, but this case is simple and innocuous enough that
>> I don't think it can do harm.
>
>>> Bootstrapped and regtested on x86_64-pc-linux-gnu.
>>> OK for trunk?
>
> OK.
Committed.
>>> If so, would it make sense to add -Wcatch-value=1 to -Wextra or even -Wall?
>>> I would do this in a seperate patch, becuase I haven't checked what that
>>> would mean for the testsuite.
>>
>> I can't think of a use case for polymorphic slicing that's not
>> harmful so unless there is a common one that escapes me, I'd say
>> -Wall.
>
> Agreed. But then you'll probably want to allow -Wno-catch-value to turn it
> off.
>
> Jason
So how about the following then?
Bootstrapped and regtested on x86_64-pc-linux-gnu.
OK for trunk?
Regards,
Volker
2017-05-30 Volker Reichelt <v.reich...@netcologne.de>
* doc/invoke.texi (-Wcatch-value): Document new shortcut.
Add to -Wall section.
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 248585)
+++ gcc/doc/invoke.texi (working copy)
@@ -265,8 +265,8 @@
-Wno-builtin-declaration-mismatch @gol
-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
-Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align -Wcast-qual @gol
--Wchar-subscripts -Wchkp -Wcatch-value=@var{n} -Wclobbered -Wcomment @gol
--Wconditionally-supported @gol
+-Wchar-subscripts -Wchkp -Wcatch-value -Wcatch-value=@var{n} @gol
+-Wclobbered -Wcomment -Wconditionally-supported @gol
-Wconversion -Wcoverage-mismatch -Wno-cpp -Wdangling-else -Wdate-time @gol
-Wdelete-incomplete @gol
-Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init @gol
@@ -3757,6 +3757,7 @@
-Wbool-compare @gol
-Wbool-operation @gol
-Wc++11-compat -Wc++14-compat @gol
+-Wcatch-value @r{(C++ and Objective-C++ only)} @gol
-Wchar-subscripts @gol
-Wcomment @gol
-Wduplicate-decl-specifier @r{(C and Objective-C only)} @gol
@@ -5834,13 +5835,16 @@
literals to @code{char *}. This warning is enabled by default for C++
programs.
-@item -Wcatch-value=@var{n} @r{(C++ and Objective-C++ only)}
+@item -Wcatch-value
+@itemx -Wcatch-value=@var{n} @r{(C++ and Objective-C++ only)}
@opindex Wcatch-value
+@opindex Wno-catch-value
Warn about catch handlers that do not catch via reference.
-With @option{-Wcatch-value=1} warn about polymorphic class types that
-are caught by value. With @option{-Wcatch-value=2} warn about all class
-types that are caught by value. With @option{-Wcatch-value=3} warn about
-all types that are not caught by reference.
+With @option{-Wcatch-value=1} (or @option{-Wcatch-value} for short)
+warn about polymorphic class types that are caught by value.
+With @option{-Wcatch-value=2} warn about all class types that are caught
+by value. With @option{-Wcatch-value=3} warn about all types that are
+not caught by reference. @option{-Wcatch-value} is enabled by @option{-Wall}.
@item -Wclobbered
@opindex Wclobbered
===================================================================
2017-05-30 Volker Reichelt <v.reich...@netcologne.de>
* c.opt (Wcatch-value): New shortcut for Wcatch-value=1.
(Wcatch-value=1): Enable by -Wall.
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt (revision 248585)
+++ gcc/c-family/c.opt (working copy)
@@ -388,8 +388,12 @@
C ObjC C++ ObjC++ Var(warn_cast_qual) Warning
Warn about casts which discard qualifiers.
+Wcatch-value
+C++ ObjC++ Warning Alias(Wcatch-value=, 1, 0)
+Warn about catch handlers of non-reference type.
+
Wcatch-value=
-C++ ObjC++ Var(warn_catch_value) Warning Joined RejectNegative UInteger
+C++ ObjC++ Var(warn_catch_value) Warning Joined RejectNegative UInteger
LangEnabledBy(C++ ObjC++,Wall, 1, 0)
Warn about catch handlers of non-reference type.
Wchar-subscripts
===================================================================
