| Message ID | YjzocVZ7Lrf1tR61@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] c++: ICE with template code in constexpr [PR104284] | expand |
On 3/24/22 17:53, Marek Polacek wrote: > On Thu, Mar 24, 2022 at 11:40:11AM -0400, Jason Merrill wrote: >> On 3/18/22 17:55, Marek Polacek wrote: >>> On Fri, Mar 11, 2022 at 06:46:42PM -0500, Jason Merrill wrote: >>>> On 3/10/22 18:04, Marek Polacek wrote: >>>>> Since r9-6073 cxx_eval_store_expression preevaluates the value to >>>>> be stored, and that revealed a crash where a template code (here, >>>>> code=IMPLICIT_CONV_EXPR) leaks into cxx_eval*. >>>>> >>>>> It happens because we're performing build_vec_init while processing >>>>> a template >>>> >>>> Hmm, that seems like the bug. Where's that call coming from? >>> >>> From build_aggr_init. So we're handling e.g. >>> >>> template<class> >>> constexpr void g () { >>> constexpr S s2[]{{'a'}}; >>> } >>> >>> cp_finish_decl (decl=s2, init={{'a'}}) sees we're in processing_template_decl, >>> but also that we have a constexpr var which is not dependent, nor is its >>> initializer: >>> >>> else if (init >>> && (init_const_expr_p || DECL_DECLARED_CONSTEXPR_P (decl)) >>> && !TYPE_REF_P (type) >>> && decl_maybe_constant_var_p (decl) >>> && !(dep_init = value_dependent_init_p (init))) >>> { >>> /* This variable seems to be a non-dependent constant, so process >>> its initializer. If check_initializer returns non-null the >>> initialization wasn't constant after all. */ >>> tree init_code; >>> cleanups = make_tree_vector (); >>> init_code = check_initializer (decl, init, flags, &cleanups); >>> >>> so we call check_initializer, where we go down this path: >>> >>> init_code = build_aggr_init_full_exprs (decl, init, flags); >>> >>> build_aggr_init sees that the type of 's2' is ARRAY_TYPE, so it calls >>> build_vec_init. >>> >>> I now recall that we've discussed build_vec_init in a template in the >>> past, for example in the context of c++/93676. So I agree we ought to >>> make an effort to avoid calling build_vec_init in a template. Perhaps >>> like this: use an INIT_EXPR. With that, we should call build_vec_init >>> if needed while instantiating. Does that make any sense? >> >> Hmm. If we do that, then we get back to >> >>> if (TREE_CODE (init_code) == INIT_EXPR) >> >> in check_initializer, and pull out the same init again, and set >> LOOKUP_ALREADY_DIGESTED. But I think that's wrong, we haven't digested it >> yet. > > Yeah, that's probably no good :( > >> Maybe we could avoid entering the below block of check_initializer at all in >> this situation? >> >>> if (((type_build_ctor_call (type) || CLASS_TYPE_P (type)) >>> && !(flags & LOOKUP_ALREADY_DIGESTED) >>> && !(init && BRACE_ENCLOSED_INITIALIZER_P (init) >>> && CP_AGGREGATE_TYPE_P (type) >>> && (CLASS_TYPE_P (type) >> >> Maybe by adding || processing_template_decl here? > > That seems to work! Thanks. > > I've checked that we call build_vec_init when instantiating, so we > shouldn't be losing any of its effects. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? OK. > -- >8 -- > Since r9-6073 cxx_eval_store_expression preevaluates the value to > be stored, and that revealed a crash where a template code (here, > code=IMPLICIT_CONV_EXPR) leaks into cxx_eval*. > > It happens because we're performing build_vec_init while processing > a template, which calls get_temp_regvar which creates an INIT_EXPR. > This INIT_EXPR's RHS contains an rvalue conversion so we create an > IMPLICIT_CONV_EXPR. Its operand is not type-dependent and the whole > INIT_EXPR is not type-dependent. So we call build_non_dependent_expr > which, with -fchecking=2, calls fold_non_dependent_expr. At this > point the expression still has an IMPLICIT_CONV_EXPR, which ought to > be handled in instantiate_non_dependent_expr_internal. However, > tsubst_copy_and_build doesn't handle INIT_EXPR; it will just call > tsubst_copy which does nothing when args is null. So we fail to > replace the IMPLICIT_CONV_EXPR and ICE. > > The problem is that we call build_vec_init in a template in the > first place. We can avoid doing so by checking p_t_d before > calling build_aggr_init in check_initializer. > > PR c++/104284 > > gcc/cp/ChangeLog: > > * decl.cc (check_initializer): Don't call build_aggr_init in > a template. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp1y/constexpr-104284-1.C: New test. > * g++.dg/cpp1y/constexpr-104284-2.C: New test. > * g++.dg/cpp1y/constexpr-104284-3.C: New test. > * g++.dg/cpp1y/constexpr-104284-4.C: New test. > --- > gcc/cp/decl.cc | 4 +++ > .../g++.dg/cpp1y/constexpr-104284-1.C | 34 ++++++++++++++++++ > .../g++.dg/cpp1y/constexpr-104284-2.C | 33 +++++++++++++++++ > .../g++.dg/cpp1y/constexpr-104284-3.C | 33 +++++++++++++++++ > .../g++.dg/cpp1y/constexpr-104284-4.C | 35 +++++++++++++++++++ > 5 files changed, 139 insertions(+) > create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C > create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C > create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C > create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc > index 68741bbf5d2..69f60a6dc0f 100644 > --- a/gcc/cp/decl.cc > +++ b/gcc/cp/decl.cc > @@ -7332,6 +7332,10 @@ check_initializer (tree decl, tree init, int flags, vec<tree, va_gc> **cleanups) > && !(init && BRACE_ENCLOSED_INITIALIZER_P (init) > && CP_AGGREGATE_TYPE_P (type) > && (CLASS_TYPE_P (type) > + /* The call to build_aggr_init below could end up > + calling build_vec_init, which may break when we > + are processing a template. */ > + || processing_template_decl > || !TYPE_NEEDS_CONSTRUCTING (type) > || type_has_extended_temps (type)))) > || (DECL_DECOMPOSITION_P (decl) && TREE_CODE (type) == ARRAY_TYPE)) > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C > new file mode 100644 > index 00000000000..809c26a6161 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C > @@ -0,0 +1,34 @@ > +// PR c++/104284 > +// { dg-do compile { target c++14 } } > +// { dg-additional-options "-fchecking=2" } > + > +struct S { > + char c{}; > +}; > + > +auto x1 = [](auto) { constexpr S s[]{{}}; }; > +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; > +#if __cpp_designated_initializers >= 201707L > +auto x3 = [](auto) { constexpr S s[]{{.c = 'a'}}; }; > +#endif > +auto x4 = [](auto) { constexpr S s[]{'a'}; }; > +auto x5 = [](auto) { constexpr S s[]{{{}}}; }; > + > +template<class> > +constexpr void g () > +{ > + constexpr S s1[]{{}}; > + static_assert(s1[0].c == '\0', ""); > + constexpr S s2[]{{'a'}}; > + static_assert(s2[0].c == 'a', ""); > +#if __cpp_designated_initializers >= 201707L > + constexpr S s3[]{{.c = 'a'}}; > + static_assert(s3[0].c == 'a', ""); > +#endif > + constexpr S s4[]{'a'}; > + static_assert(s4[0].c == 'a', ""); > + constexpr S s5[]{{{}}}; > + static_assert(s5[0].c == '\0', ""); > +} > + > +static_assert ((g<int>(), true), ""); > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C > new file mode 100644 > index 00000000000..704d37de129 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C > @@ -0,0 +1,33 @@ > +// PR c++/104284 > +// { dg-do compile { target c++14 } } > +// { dg-additional-options "-fchecking=2" } > + > +struct S { > + char a; > + constexpr S() : a{'a'} { } > + constexpr S(char a_) : a{a_} { } > +}; > + > +auto x1 = [](auto) { constexpr S s[]{{}}; }; > +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; > +auto x3 = [](auto) { constexpr S s[]{'a'}; }; > +auto x4 = [](auto) { constexpr S s[]{{{}}}; }; > + > +template<typename> > +constexpr void g() > +{ > + constexpr S s1[]{{}}; > + static_assert(s1[0].a == 'a', ""); > + constexpr S s2[]{{'a'}}; > + static_assert(s2[0].a == 'a', ""); > + constexpr S s3[]{'a'}; > + static_assert(s3[0].a == 'a', ""); > + constexpr S s4[]{{{}}}; > + static_assert(s4[0].a == '\0', ""); > +} > + > +void > +f () > +{ > + g<int>(); > +} > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C > new file mode 100644 > index 00000000000..6f23b255f9c > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C > @@ -0,0 +1,33 @@ > +// PR c++/104284 > +// { dg-do compile { target c++14 } } > +// { dg-additional-options "-fchecking=2" } > +// Like constexpr-104284.C, but the function template is not > +// constexpr. In that case, we were still calling build_vec_init > +// in a template, just not crashing. > + > +struct S { > + char c{}; > +}; > + > +template<class> > +void g () > +{ > + constexpr S s1[]{{}}; > + static_assert(s1[0].c == '\0', ""); > + constexpr S s2[]{{'a'}}; > + static_assert(s2[0].c == 'a', ""); > +#if __cpp_designated_initializers >= 201707L > + constexpr S s3[]{{.c = 'a'}}; > + static_assert(s3[0].c == 'a', ""); > +#endif > + constexpr S s4[]{'a'}; > + static_assert(s4[0].c == 'a', ""); > + constexpr S s5[]{{{}}}; > + static_assert(s5[0].c == '\0', ""); > +} > + > +void > +f () > +{ > + g<int>(); > +} > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C > new file mode 100644 > index 00000000000..a99d3255a47 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C > @@ -0,0 +1,35 @@ > +// PR c++/104284 > +// { dg-do run { target c++14 } } > +// { dg-additional-options "-fchecking=2" } > + > +struct S { > + char c{}; > +}; > + > +template<class> > +constexpr void g () > +{ > + S s1[]{{}}; > + if (s1[0].c != '\0') > + __builtin_abort (); > + S s2[]{{'a'}}; > + if (s2[0].c != 'a') > + __builtin_abort (); > +#if __cpp_designated_initializers >= 201707L > + S s3[]{{.c = 'a'}}; > + if (s3[0].c != 'a') > + __builtin_abort (); > +#endif > + S s4[]{'a'}; > + if (s4[0].c != 'a') > + __builtin_abort (); > + S s5[]{{{}}}; > + if (s5[0].c != '\0') > + __builtin_abort (); > +} > + > +int > +main () > +{ > + g<int>(); > +} > > base-commit: 346ab5a54a831ad9c78afcbd8dfe98e0e07e3070
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index 68741bbf5d2..69f60a6dc0f 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -7332,6 +7332,10 @@ check_initializer (tree decl, tree init, int flags, vec<tree, va_gc> **cleanups) && !(init && BRACE_ENCLOSED_INITIALIZER_P (init) && CP_AGGREGATE_TYPE_P (type) && (CLASS_TYPE_P (type) + /* The call to build_aggr_init below could end up + calling build_vec_init, which may break when we + are processing a template. */ + || processing_template_decl || !TYPE_NEEDS_CONSTRUCTING (type) || type_has_extended_temps (type)))) || (DECL_DECOMPOSITION_P (decl) && TREE_CODE (type) == ARRAY_TYPE)) diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C new file mode 100644 index 00000000000..809c26a6161 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C @@ -0,0 +1,34 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char c{}; +}; + +auto x1 = [](auto) { constexpr S s[]{{}}; }; +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; +#if __cpp_designated_initializers >= 201707L +auto x3 = [](auto) { constexpr S s[]{{.c = 'a'}}; }; +#endif +auto x4 = [](auto) { constexpr S s[]{'a'}; }; +auto x5 = [](auto) { constexpr S s[]{{{}}}; }; + +template<class> +constexpr void g () +{ + constexpr S s1[]{{}}; + static_assert(s1[0].c == '\0', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].c == 'a', ""); +#if __cpp_designated_initializers >= 201707L + constexpr S s3[]{{.c = 'a'}}; + static_assert(s3[0].c == 'a', ""); +#endif + constexpr S s4[]{'a'}; + static_assert(s4[0].c == 'a', ""); + constexpr S s5[]{{{}}}; + static_assert(s5[0].c == '\0', ""); +} + +static_assert ((g<int>(), true), ""); diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C new file mode 100644 index 00000000000..704d37de129 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C @@ -0,0 +1,33 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char a; + constexpr S() : a{'a'} { } + constexpr S(char a_) : a{a_} { } +}; + +auto x1 = [](auto) { constexpr S s[]{{}}; }; +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; +auto x3 = [](auto) { constexpr S s[]{'a'}; }; +auto x4 = [](auto) { constexpr S s[]{{{}}}; }; + +template<typename> +constexpr void g() +{ + constexpr S s1[]{{}}; + static_assert(s1[0].a == 'a', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].a == 'a', ""); + constexpr S s3[]{'a'}; + static_assert(s3[0].a == 'a', ""); + constexpr S s4[]{{{}}}; + static_assert(s4[0].a == '\0', ""); +} + +void +f () +{ + g<int>(); +} diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C new file mode 100644 index 00000000000..6f23b255f9c --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C @@ -0,0 +1,33 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } +// Like constexpr-104284.C, but the function template is not +// constexpr. In that case, we were still calling build_vec_init +// in a template, just not crashing. + +struct S { + char c{}; +}; + +template<class> +void g () +{ + constexpr S s1[]{{}}; + static_assert(s1[0].c == '\0', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].c == 'a', ""); +#if __cpp_designated_initializers >= 201707L + constexpr S s3[]{{.c = 'a'}}; + static_assert(s3[0].c == 'a', ""); +#endif + constexpr S s4[]{'a'}; + static_assert(s4[0].c == 'a', ""); + constexpr S s5[]{{{}}}; + static_assert(s5[0].c == '\0', ""); +} + +void +f () +{ + g<int>(); +} diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C new file mode 100644 index 00000000000..a99d3255a47 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C @@ -0,0 +1,35 @@ +// PR c++/104284 +// { dg-do run { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char c{}; +}; + +template<class> +constexpr void g () +{ + S s1[]{{}}; + if (s1[0].c != '\0') + __builtin_abort (); + S s2[]{{'a'}}; + if (s2[0].c != 'a') + __builtin_abort (); +#if __cpp_designated_initializers >= 201707L + S s3[]{{.c = 'a'}}; + if (s3[0].c != 'a') + __builtin_abort (); +#endif + S s4[]{'a'}; + if (s4[0].c != 'a') + __builtin_abort (); + S s5[]{{{}}}; + if (s5[0].c != '\0') + __builtin_abort (); +} + +int +main () +{ + g<int>(); +}