| Message ID | 20200326193930.GN2156@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Avoid calls in non-evaluated contexts affect whether function can or can't throw [PR94326] | expand |
On 3/26/20 3:39 PM, Jakub Jelinek wrote: > Hi! > > The following testcase FAILs -fcompare-debug, because if we emit a > -Wreturn-local-addr warning, we tsubst decltype in order to print the > warning and as that function could throw, set_flags_from_callee during that > sets cp_function_chain->can_throw and later on we don't set TREE_NOTHROW > on foo. While with -w or -Wno-return-local-addr, tsubst isn't called during > the warning_at, cp_function_chain->can_throw is kept clear and TREE_NOTHROW > is set on foo. > It isn't just a matter of the warning though, in > int foo (); > int bar () { return sizeof (foo ()); } > int baz () { return sizeof (int); } > I don't really see why we should mark only baz as TREE_NOTHROW and not bar > too, when neither can really throw. > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for > trunk? OK. > 2020-03-26 Jakub Jelinek <jakub@redhat.com> > > PR c++/94326 > * call.c (set_flags_from_callee): Don't update > cp_function_chain->can_throw or current_function_returns_abnormally > if cp_unevaluated_operand. > > * g++.dg/other/pr94326.C: New test. > > --- gcc/cp/call.c.jj 2020-03-25 08:05:07.153731580 +0100 > +++ gcc/cp/call.c 2020-03-26 15:03:42.432909693 +0100 > @@ -333,11 +333,14 @@ set_flags_from_callee (tree call) > && internal_fn_flags (CALL_EXPR_IFN (call)) & ECF_NOTHROW) > nothrow = true; > > - if (!nothrow && at_function_scope_p () && cfun && cp_function_chain) > - cp_function_chain->can_throw = 1; > + if (cfun && cp_function_chain && !cp_unevaluated_operand) > + { > + if (!nothrow && at_function_scope_p ()) > + cp_function_chain->can_throw = 1; > > - if (decl && TREE_THIS_VOLATILE (decl) && cfun && cp_function_chain) > - current_function_returns_abnormally = 1; > + if (decl && TREE_THIS_VOLATILE (decl)) > + current_function_returns_abnormally = 1; > + } > > TREE_NOTHROW (call) = nothrow; > } > --- gcc/testsuite/g++.dg/other/pr94326.C.jj 2020-03-26 15:14:23.609400216 +0100 > +++ gcc/testsuite/g++.dg/other/pr94326.C 2020-03-26 15:14:54.162947065 +0100 > @@ -0,0 +1,19 @@ > +// PR c++/94326 > +// { dg-do compile { target c++11 } } > +// { dg-options "-fcompare-debug" } > + > +template <typename = int> struct A { > + const int &foo() { return 0; } // { dg-warning "returning reference to temporary" } > + template <typename _Kt> void bar(_Kt) { foo(); } > +}; > +struct B { > + A<> b; > + template <typename _Kt> auto baz(_Kt p1) -> decltype(b.bar(p1)) { > + b.bar(p1); > + } > +}; > +struct C {}; > +void operator<(C, int) { > + B a; > + a.baz(C{}); > +} > > Jakub >
--- gcc/cp/call.c.jj 2020-03-25 08:05:07.153731580 +0100 +++ gcc/cp/call.c 2020-03-26 15:03:42.432909693 +0100 @@ -333,11 +333,14 @@ set_flags_from_callee (tree call) && internal_fn_flags (CALL_EXPR_IFN (call)) & ECF_NOTHROW) nothrow = true; - if (!nothrow && at_function_scope_p () && cfun && cp_function_chain) - cp_function_chain->can_throw = 1; + if (cfun && cp_function_chain && !cp_unevaluated_operand) + { + if (!nothrow && at_function_scope_p ()) + cp_function_chain->can_throw = 1; - if (decl && TREE_THIS_VOLATILE (decl) && cfun && cp_function_chain) - current_function_returns_abnormally = 1; + if (decl && TREE_THIS_VOLATILE (decl)) + current_function_returns_abnormally = 1; + } TREE_NOTHROW (call) = nothrow; } --- gcc/testsuite/g++.dg/other/pr94326.C.jj 2020-03-26 15:14:23.609400216 +0100 +++ gcc/testsuite/g++.dg/other/pr94326.C 2020-03-26 15:14:54.162947065 +0100 @@ -0,0 +1,19 @@ +// PR c++/94326 +// { dg-do compile { target c++11 } } +// { dg-options "-fcompare-debug" } + +template <typename = int> struct A { + const int &foo() { return 0; } // { dg-warning "returning reference to temporary" } + template <typename _Kt> void bar(_Kt) { foo(); } +}; +struct B { + A<> b; + template <typename _Kt> auto baz(_Kt p1) -> decltype(b.bar(p1)) { + b.bar(p1); + } +}; +struct C {}; +void operator<(C, int) { + B a; + a.baz(C{}); +}
Hi! The following testcase FAILs -fcompare-debug, because if we emit a -Wreturn-local-addr warning, we tsubst decltype in order to print the warning and as that function could throw, set_flags_from_callee during that sets cp_function_chain->can_throw and later on we don't set TREE_NOTHROW on foo. While with -w or -Wno-return-local-addr, tsubst isn't called during the warning_at, cp_function_chain->can_throw is kept clear and TREE_NOTHROW is set on foo. It isn't just a matter of the warning though, in int foo (); int bar () { return sizeof (foo ()); } int baz () { return sizeof (int); } I don't really see why we should mark only baz as TREE_NOTHROW and not bar too, when neither can really throw. Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2020-03-26 Jakub Jelinek <jakub@redhat.com> PR c++/94326 * call.c (set_flags_from_callee): Don't update cp_function_chain->can_throw or current_function_returns_abnormally if cp_unevaluated_operand. * g++.dg/other/pr94326.C: New test. Jakub