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C++ PATCH to add -Wno-noexcept-type

Message ID CADzB+2mrxRXoAY4o=d4+MHU8iiKyzh64iCg3Rai=UeX=ZyEyUQ@mail.gmail.com
State New
Headers show

Commit Message

Jason Merrill March 4, 2017, 8:01 a.m. UTC 
Along with the C++17 change to make noexcept part of the type I added
a warning for situations where this changes the mangled name of a
symbol, as part of -Wc++1z-compat.  This is troublesome since there's
no way to adjust your code to avoid it, so this patch gives it a
separate flag.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit aba02f8c8b29b8355e3c72c0ba6bc000768a8939
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Mar 3 15:07:31 2017 -1000

            * c.opt (Wnoexcept-type): New.
    
    gcc/cp/
            * mangle.c (mangle_decl): Check -Wnoexcept-type instead of
            -Wc++1z-compat.
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Patch

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index cf459ab..78fea61 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -780,6 +780,10 @@  Wnoexcept
 C++ ObjC++ Var(warn_noexcept) Warning
 Warn when a noexcept expression evaluates to false even though the expression can't actually throw.
 
+Wnoexcept-type
+C++ ObjC++ Warning Var(warn_noexcept_type) LangEnabledBy(C++ ObjC++,Wabi || Wc++1z-compat)
+Warn if C++1z noexcept function type will change the mangled name of a symbol.
+
 Wnon-template-friend
 C++ ObjC++ Var(warn_nontemplate_friend) Init(1) Warning
 Warn when non-templatized friend functions are declared within a template.
diff --git a/gcc/cp/mangle.c b/gcc/cp/mangle.c
index 8b30f42..6f7e21c 100644
--- a/gcc/cp/mangle.c
+++ b/gcc/cp/mangle.c
@@ -3856,7 +3856,7 @@  mangle_decl (const tree decl)
 
   if (G.need_cxx1z_warning
       && (TREE_PUBLIC (decl) || DECL_REALLY_EXTERN (decl)))
-    warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wc__1z_compat,
+    warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wnoexcept_type,
 		"mangled name for %qD will change in C++17 because the "
 		"exception specification is part of a function type",
 		decl);
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 68174a1..15eb0e0 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -215,7 +215,7 @@  in the following sections.
 -Wabi=@var{n}  -Wabi-tag  -Wconversion-null  -Wctor-dtor-privacy @gol
 -Wdelete-non-virtual-dtor  -Wliteral-suffix  -Wmultiple-inheritance @gol
 -Wnamespaces  -Wnarrowing @gol
--Wnoexcept  -Wnon-virtual-dtor  -Wreorder  -Wregister @gol
+-Wnoexcept  -Wnoexcept-type  -Wnon-virtual-dtor  -Wreorder  -Wregister @gol
 -Weffc++  -Wstrict-null-sentinel  -Wtemplates @gol
 -Wno-non-template-friend  -Wold-style-cast @gol
 -Woverloaded-virtual  -Wno-pmf-conversions @gol
@@ -2897,6 +2897,20 @@  to a function that does not have a non-throwing exception
 specification (i.e. @code{throw()} or @code{noexcept}) but is known by
 the compiler to never throw an exception.
 
+@item -Wnoexcept @r{(C++ and Objective-C++ only)}
+@opindex Wnoexcept-type
+@opindex Wno-noexcept-type
+Warn if the C++1z feature making @code{noexcept} part of a function
+type changes the mangled name of a symbol relative to C++14.  Enabled
+by @option{-Wabi} and @option{-Wc++1z-compat}.
+
+@smallexample
+template <class T> void f(T t) @{ t(); @};
+void g() noexcept;
+void h() @{ f(g); @} // in C++14 calls f<void(*)()>, in C++1z calls f<void(*)()noexcept>
+@end smallexample
+
+
 @item -Wnon-virtual-dtor @r{(C++ and Objective-C++ only)}
 @opindex Wnon-virtual-dtor
 @opindex Wno-non-virtual-dtor
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type11a.C b/gcc/testsuite/g++.dg/cpp1z/noexcept-type11a.C
new file mode 100644
index 0000000..f5028d2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type11a.C
@@ -0,0 +1,3 @@ 
+// { dg-options "-Wall -Wno-noexcept-type -std=c++14" }
+
+void f(int(*)() noexcept) { }