[Bug c++/64931] New: ICE on function with deduced return type and input is instantiated template class

[Bug c++/64931] New: ICE on function with deduced return type and input is instantiated template class

[sneves at dei dot uc.pt]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64931

            Bug ID: 64931
           Summary: ICE on function with deduced return type and input is
                    instantiated template class
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sneves at dei dot uc.pt

Minimal example:

template<typename T, unsigned long N>
struct array {
  T data[N];
};

auto copy(array<int, 32> const& x) {
  return x;
}

This only seems to result in ICE if a) `copy` has deduced return type with
value semantics, i.e. `auto` but not `decltype(auto)`, and b) if the `array`
struct is a template, and `copy` takes in a specific instantiation of `array`.
Verified to ICE in GCC 4.8.2, 4.9.2, and 5.0.0 20150202.

[Bug c++/64931] ICE on function with deduced return type and input is instantiated template class

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64931

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-04
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
f.cc: In function ‘auto copy(const array<int, 32ul>&)’:
f.cc:7:10: internal compiler error: Segmentation fault
   return x;
          ^
0xca615f crash_signal
        /home/jwakely/src/gcc/gcc/gcc/toplev.c:383
0xabb836 gimplify_return_expr
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:1280
0xaa8510 gimplify_expr(tree_node**, gimple_statement_base**,
gimple_statement_base**, bool (*)(tree_node*), int)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:8144
0xaabdb6 gimplify_stmt(tree_node**, gimple_statement_base**)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:5514
0xaa7750 gimplify_cleanup_point_expr
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:5290
0xaa7750 gimplify_expr(tree_node**, gimple_statement_base**,
gimple_statement_base**, bool (*)(tree_node*), int)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:8260
0xaabdb6 gimplify_stmt(tree_node**, gimple_statement_base**)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:5514
0xaad72d gimplify_body(tree_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:9048
0xaadd86 gimplify_function_tree(tree_node*)
        /home/jwakely/src/gcc/gcc/gcc/gimplify.c:9202
0x8ed6d7 cgraph_node::analyze()
        /home/jwakely/src/gcc/gcc/gcc/cgraphunit.c:633
0x8f0406 analyze_functions
        /home/jwakely/src/gcc/gcc/gcc/cgraphunit.c:1023
0x8f0b75 symbol_table::finalize_compilation_unit()
        /home/jwakely/src/gcc/gcc/gcc/cgraphunit.c:2435
0x6bcde0 cp_write_global_declarations()
        /home/jwakely/src/gcc/gcc/gcc/cp/decl2.c:4754
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From: "albert.astals at canonical dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/65309] [Regression] Executes wrong function inside an anonymous namespace on runtime
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide309

--- Comment #3 from Albert Astals Cid <albert.astals at canonical dot com> ---
I guess i'm using the system default one, that would be

$ `which ld` -V
GNU ld (GNU Binutils for Ubuntu) 2.25
  Supported emulations:
   elf_x86_64
   elf32_x86_64
   elf_i386
   i386linux
   elf_l1om
   elf_k1om
   i386pep
   i386pe

I'm not the only one with this problem, doesn't seem to be Ubuntu specific
either, see
http://lists.qt-project.org/pipermail/development/2015-March/020632.html

[Bug c++/64931] ICE on function with deduced return type and input is instantiated template class

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64931

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Slightly more reduced:

template<typename T>
struct S {
  T data[32];
};

auto
foo (S<int> & x)
{
  return x;
}

The problem is that we create a RESULT_DECL with NULL DECL_SIZE, and gimplifier
ICEs on that.  The RESULT_DECL is created in convert_for_initialization called
from check_return_expr I think.