https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69496
Bug ID: 69496
Summary: [C++ 14] ICE on VLA in constexpr function
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
In C++ 14 mode (but not prior) GCC 5 and 6 fail with an ICE on the program
below. It's not clear to me whether this is supposed to be accepted by G++.
Clang rejects the test case because it doesn't allow VLAs to be initialized in
any context, but G++ otherwise silently accepts VLA initialization.
$ cat t.c && /home/msebor/build/gcc-trunk-svn/gcc/xgcc
-B/home/msebor/build/gcc-trunk-svn/gcc -Wall -Wextra -Wpedantic -xc++ t.c
constexpr int foo (int n)
{
int a [n] = { };
int z = 0;
for (unsigned i = 0; i != sizeof (a); ++i)
z += a [i];
return z;
}
constexpr int n = foo (1);
t.c: In function ‘constexpr int foo(int)’:
t.c:3:13: warning: ISO C++ forbids variable length array ‘a’ [-Wvla]
int a [n] = { };
^
t.c: At global scope:
t.c:13:23: in constexpr expansion of ‘foo(1)’
t.c:13:25: internal compiler error: tree check: expected integer_cst, have
plus_expr in get_len, at tree.h:5250
constexpr int n = foo (1);
^
0x13c08a4 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
/home/msebor/scm/fsf/gcc-svn/gcc/tree.c:9605
0x7755ef tree_check(tree_node const*, char const*, int, char const*, tree_code)
/home/msebor/scm/fsf/gcc-svn/gcc/tree.h:3262
0x79c5f3 wi::extended_tree<192>::get_len() const
/home/msebor/scm/fsf/gcc-svn/gcc/tree.h:5250
0x79c454 wi::int_traits<generic_wide_int<wi::extended_tree<192> >
>::decompose(long*, unsigned int, generic_wide_int<wi::extended_tree<192> >
const&)
/home/msebor/scm/fsf/gcc-svn/gcc/wide-int.h:898
0x79c084
wide_int_ref_storage<true>::wide_int_ref_storage<generic_wide_int<wi::extended_tree<192>
> >(generic_wide_int<wi::extended_tree<192> > const&, unsigned int)
/home/msebor/scm/fsf/gcc-svn/gcc/wide-int.h:945
0x79bcb6 generic_wide_int<wide_int_ref_storage<true>
>::generic_wide_int<generic_wide_int<wi::extended_tree<192> >
>(generic_wide_int<wi::extended_tree<192> > const&, unsigned int)
/home/msebor/scm/fsf/gcc-svn/gcc/wide-int.h:722
0x79b6dc bool wi::lts_p<generic_wide_int<wi::extended_tree<192> >,
generic_wide_int<wi::extended_tree<192> >
>(generic_wide_int<wi::extended_tree<192> > const&,
generic_wide_int<wi::extended_tree<192> > const&)
/home/msebor/scm/fsf/gcc-svn/gcc/wide-int.h:1749
0x79b46a tree_int_cst_lt(tree_node const*, tree_node const*)
/home/msebor/scm/fsf/gcc-svn/gcc/tree.h:5300
0xa44235 cxx_eval_array_reference
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:1858
0xa4aa7e cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3550
0xa434c4 cxx_eval_binary_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:1610
0xa4a9a9 cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3527
0xa48693 cxx_eval_store_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:2886
0xa4a2b3 cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3356
0xa4aceb cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3615
0xa4a4d6 cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3395
0xa4a4d6 cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3395
0xa48f0d cxx_eval_statement_list
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3071
0xa4903d cxx_eval_loop_expr
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3098
0xa4b57d cxx_eval_constant_expression
/home/msebor/scm/fsf/gcc-svn/gcc/cp/constexpr.c:3723
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with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
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