On 3/24/22 13:03, Marek Polacek wrote:
On Thu, Mar 24, 2022 at 09:32:19AM -0400, Jason Merrill wrote:
On 3/23/22 19:26, Marek Polacek wrote:
On Wed, Mar 23, 2022 at 04:35:32PM -0400, Jason Merrill wrote:
On 3/22/22 19:55, Marek Polacek wrote:
This is a crash where a FIX_TRUNC_EXPR gets into tsubst_copy_and_build
where it hits gcc_unreachable ().
The history of tsubst_copy_and_build/FIX_TRUNC_EXPR is such that it
was introduced in r181478, but it did the wrong thing, whereupon it
was turned into gcc_unreachable () in r258821 (see this thread:
<https://gcc.gnu.org/pipermail/gcc-patches/2018-March/495853.html>).
In a template, we should never create a FIX_TRUNC_EXPR (that's what
conv_unsafe_in_template_p is for). But in this test we are NOT in
a template when we call digest_nsdmi_init which ends up calling
convert_like, converting 1.0e+0 to int, so convert_to_integer_1
gives us a FIX_TRUNC_EXPR.
But then when we get to parsing f's parameters, we are in a template
when processing decltype(Helpers{}), and since r268321, when the
compound literal isn't instantiation-dependent and the type isn't
type-dependent, finish_compound_literal falls back to the normal
processing, so it calls digest_init, which does fold_non_dependent_init
and since the FIX_TRUNC_EXPR isn't dependent, we instantiate and
therefore crash in tsubst_copy_and_build.
Hmm, we shouldn't be doing fold_non_dependent_init on the result of
get_nsdmi. Why does that happen?
OK, so we have decltype(Helpers{}), finish_compound_literal gets
Helpers{}, it's not type-dependent, so:
- call digest_init (type=Helpers, init={})
init is BRACE_ENCLOSED_INITIALIZER_P, type is !TYPE_NON_AGGREGATE_CLASS
so go down to...
- process_init_constructor_record (type=Helpers, init={})
- we walk the fields of Helpers, there's 'inputs' of type knob_t
type_build_ctor_call (knob_t) is true, we want to default-init this
field
- create a {} as the init for default-initialization
- call massage_init_elt (type=knob_t, init={}) to adjust the init
- we do so by calling digest_init_r (type=knob_t, init={})
- here we again call process_init_constructor_record, walk knob_t's
fields, see the field 'value', it has a DECL_INITIAL, so call
get_nsdmi, that returns the FIX_TRUNC_EXPR we've created before
- so digesting {} for knob_t produced
init = {.value=(int) NON_LVALUE_EXPR <1.0e+0>}
- then we call fold_non_dependent_init on this init, and die
Maybe we shouldn't call fold_non_dependent_init on a CONSTRUCTOR here, since
presumably we already called it on elements that needed it in the recursive
digest_init_r.
Ah, that works. It's still a bit weird that we don't treat FLOAT_EXPR and
FIX_TRUNC_EXPR the same.
I've tried to remove the call to fold_non_dependent_init in massage_init_elt
to see what breaks...a lot. So it has to stay at least in this form.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
Thanks,
-- >8 --
This is a crash where a FIX_TRUNC_EXPR gets into tsubst_copy_and_build
where it hits gcc_unreachable ().
The history of tsubst_copy_and_build/FIX_TRUNC_EXPR is such that it
was introduced in r181478, but it did the wrong thing, whereupon it
was turned into gcc_unreachable () in r258821 (see this thread:
<https://gcc.gnu.org/pipermail/gcc-patches/2018-March/495853.html>).
In a template, we should never create a FIX_TRUNC_EXPR (that's what
conv_unsafe_in_template_p is for). But in this test we are NOT in
a template when we call digest_nsdmi_init which ends up calling
convert_like, converting 1.0e+0 to int, so convert_to_integer_1
gives us a FIX_TRUNC_EXPR.
But then when we get to parsing f's parameters, we are in a template
when processing decltype(Helpers{}), and since r268321, when the
compound literal isn't instantiation-dependent and the type isn't
type-dependent, finish_compound_literal falls back to the normal
processing, so it calls digest_init, which does fold_non_dependent_init
and since the FIX_TRUNC_EXPR isn't dependent, we instantiate and
therefore crash in tsubst_copy_and_build.
The fateful call to fold_non_dependent_init comes from massage_init_elt,
We shouldn't be calling f_n_d_i on the result of get_nsdmi. This we can
avoid by eschewing calling f_n_d_i on CONSTRUCTORs; their elements have
already been folded.
PR c++/102990
gcc/cp/ChangeLog:
* typeck2.cc (massage_init_elt): Avoid folding CONSTRUCTORs.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/nsdmi-template22.C: New test.
* g++.dg/cpp0x/nsdmi-template23.C: New test.
---
gcc/cp/typeck2.cc | 13 +++++++++----
gcc/testsuite/g++.dg/cpp0x/nsdmi-template22.C | 13 +++++++++++++
gcc/testsuite/g++.dg/cpp0x/nsdmi-template23.C | 13 +++++++++++++
3 files changed, 35 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template22.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template23.C
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index a4c825fc34d..cebe6acf487 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -1433,10 +1433,15 @@ massage_init_elt (tree type, tree init, int nested, int
flags,
new_flags |= LOOKUP_AGGREGATE_PAREN_INIT;
init = digest_init_r (type, init, nested ? 2 : 1, new_flags, complain);
/* When we defer constant folding within a statement, we may want to
- defer this folding as well. */
- tree t = fold_non_dependent_init (init, complain);
- if (TREE_CONSTANT (t))
- init = t;
+ defer this folding as well. Don't call this on CONSTRUCTORs because
+ their elements have already been folded, and we must avoid folding
+ the result of get_nsdmi. */
+ if (TREE_CODE (init) != CONSTRUCTOR)
+ {
+ tree t = fold_non_dependent_init (init, complain);
+ if (TREE_CONSTANT (t))
+ init = t;
+ }
return init;
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template22.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template22.C
new file mode 100644
index 00000000000..4ed2501035c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template22.C
@@ -0,0 +1,13 @@
+// PR c++/102990
+// { dg-do compile { target c++11 } }
+
+struct knob_t {
+ /* Let's create a FIX_TRUNC_EXPR. */
+ int value = 1.0;
+};
+
+struct Helpers {
+ knob_t inputs;
+};
+
+template<class> void f(decltype(Helpers{}));
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template23.C
b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template23.C
new file mode 100644
index 00000000000..240cab4347a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template23.C
@@ -0,0 +1,13 @@
+// PR c++/102990
+// { dg-do compile { target c++11 } }
+
+struct knob_t {
+ /* Let's create a FLOAT_EXPR. */
+ double value = 1UL;
+};
+
+struct Helpers {
+ knob_t inputs;
+};
+
+template<class> void f(decltype(Helpers{}));
base-commit: fb488cba571539b6644e8f99f1dd997cdb4c82c1
