Internal error in varasm.c

Created attachment 42024
unincluded unreduced testcase

> g++-7 -std=gnu++1z -S floc.cc
floc.cc:187:1: internal compiler error: in output_constructor_regular_field, at varasm.c:5030
    continue;
 ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugs.opensuse.org/> for instructions.

same ICE with gcc 6 and trunk.

Confirmed for following reduced test-case:

$ cat pr81922.ii
struct
{
  char *a;
  char b[];
} c[]{"", "", {}};

started with r234636. Is the original test-case really valid?

We have a bunch of other PRs for the lack of diagnostics of invalid initialization of flexible array members inside of arrays to non-empty array.
We just should diagnose it as invalid.

Created attachment 42811
gcc8-pr81922.patch

WIP patch that attempts to handle it like the C FE, will work on testcases tomorrow.

Author: jakub
Date: Fri Dec 15 20:20:00 2017
New Revision: 255703

URL: https://gcc.gnu.org/viewcvs?rev=255703&root=gcc&view=rev
Log:
 PR c++/80135
 PR c++/81922
 * typeck2.c (digest_init_r): Change nested argument type from bool to
 int. Use code instead of TREE_CODE (type) where possible. If
 nested == 2, diagnose initialization of flexible array member with
 STRING_CST. Pass nested to process_init_constructor. Formatting fix.
 (digest_init, digest_init_flags): Adjust digest_init_r caller.
 (massage_init_elt): Add nested argument. Pass 2 instead of 1 to
 digest_init_r's nested argument if nested is non-zero.
 (process_init_constructor_array): Add nested argument. If nested == 2,
 diagnose initialization of flexible array member with non-empty
 braced enclosed list. Pass nested to massage_init_elt.
 (process_init_constructor_record, process_init_constructor_union): Add
 nested argument, pass it to massage_init_elt.
 (process_init_constructor): Add nested argument, pass it to
 process_init_constructor_{array,record,union}.
 * init.c (find_field_init): Renamed to ...
 (find_flexarray_init): ... this. Return NULL_TREE if init is
 error_mark_node. Don't look through nested CONSTRUCTORs.
 (warn_placement_new_too_small): Adjust caller.

 * g++.dg/warn/Wplacement-new-size-1.C (fBx1): Initialize nested
 flexible array member only with {}. Add dg-warning.
 (fBx2, fBx3): Remove.
 * g++.dg/warn/Wplacement-new-size-2.C (fBx1): Initialize nested
 flexible array member only with {}. Add dg-warning.
 (fBx2, fBx3): Remove.
 * g++.dg/warn/Wplacement-new-size-6.C: New test.
 * g++.dg/ext/flexary13.C (main): Remove test for initialization
 of nested flexible array member with non-empty initializer.
 * g++.dg/ext/flexary25.C: New test.
 * g++.dg/ext/flexary26.C: New test.
 * g++.dg/ext/flexary27.C: New test.
 * g++.dg/parse/pr43765.C: Expect diagnostics about initialization
 of nested flexible array member with non-empty initializer. Expect
 C++2A diagnostics about mixing of designated and non-designated
 initializers.

Added:
    trunk/gcc/testsuite/g++.dg/ext/flexary25.C
    trunk/gcc/testsuite/g++.dg/ext/flexary26.C
    trunk/gcc/testsuite/g++.dg/ext/flexary27.C
    trunk/gcc/testsuite/g++.dg/warn/Wplacement-new-size-6.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c
    trunk/gcc/cp/typeck2.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/ext/flexary13.C
    trunk/gcc/testsuite/g++.dg/parse/pr43765.C
    trunk/gcc/testsuite/g++.dg/warn/Wplacement-new-size-1.C
    trunk/gcc/testsuite/g++.dg/warn/Wplacement-new-size-2.C

Fixed on the trunk. Unsure about backports.

GCC 6 branch is being closed

Fixed in GCC 8.