[Bug libgomp/105839] New: internal compiler error: in tsubst_omp_for_iterator, at cp/pt.cc:18122 (instantiate_pending_templates -> instantiate_decl -> tsubst_lambda_expr)

[Bug libgomp/105839] New: internal compiler error: in tsubst_omp_for_iterator, at cp/pt.cc:18122 (instantiate_pending_templates -> instantiate_decl -> tsubst_lambda_expr)

[northon_patrick3 at yahoo dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

            Bug ID: 105839
           Summary: internal compiler error: in tsubst_omp_for_iterator,
                    at cp/pt.cc:18122 (instantiate_pending_templates ->
                    instantiate_decl -> tsubst_lambda_expr)
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
          Assignee: unassigned at gcc dot gnu.org
          Reporter: northon_patrick3 at yahoo dot ca
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

Created attachment 53079
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53079&action=edit
Result from -freport-bug

The code:
```
void test(const auto &b1)
{
        const auto loopImpl = [&](auto&& fc)
                {
                        #pragma omp parallel for
                        for(auto&& [v1, v2] : b1);
                };

        loopImpl([]{});
}

void test2()
{
        int a[10];
        test(a);
}
```

The command line:
```
g++ -fopenmp test.cpp
```

The error:
```
internal compiler error: in tsubst_omp_for_iterator, at cp/pt.cc:18126
   11 |                         for(auto&& [v1, v2] : b1);
      |                         ^~~
0x1ac4724 internal_error(char const*, ...)
        ???:0
0x663b55 fancy_abort(char const*, int, char const*)
        ???:0
0x81d054 tsubst_lambda_expr(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x80614a tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ???:0
0x7fedbe instantiate_decl(tree_node*, bool, bool)
        ???:0
0x81e704 instantiate_pending_templates(int)
        ???:0
0x7173d1 c_parse_final_cleanups()
        ???:0
```

GCC is configured with:

```
configure --prefix=/opt/pat-gcc --libdir=/opt/pat-gcc/lib
--libexecdir=/opt/pat-gcc/lib --enable-languages=c,c++,lto --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
gdc_include_dir=/opt/pat-gcc/include/dlang/gdc
```

It happens from version 10.1 to latest commit at this date.

It no longer crash if:
- I don't use structured bindings.
- b1 isn't a template.
- I remove `auto&& fc`.

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator, at cp/pt.cc:18122 (instantiate_pending_templates -> instantiate_decl -> tsubst_lambda_expr)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Adjusted testcase, so that it is already valid C++17:
template <typename T>
void
foo (const T &x)
{
  [&] (auto&& y)
  {
    #pragma omp parallel for
    for (auto&& [v1, v2] : x)
      ;
  } ([]{});
}

void
bar ()
{
  int a[10];
  foo (a);
}

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator with openmp and structured bindings in a template

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|ice-on-valid-code           |

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Actually, I don't see how it can be valid.
x (or b1) is const int[10] & and structured binding on int is clearly invalid.
The ICE got fixed in r13-4460-gee4f25999f6832a1c, except that since
r13-5379-gd427407a199a0c276cb02 we ICE again with -fopenmp -std=c++11 (error
recovery
after emitting some errors).

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator with openmp and structured bindings in a template

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 54564
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54564&action=edit
gcc13-pr105839.patch

Untested fix for the error recovery issue.

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator with openmp and structured bindings in a template

[northon_patrick3 at yahoo dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

--- Comment #4 from northon_patrick3 at yahoo dot ca ---
Actually is still crash even on valid code:

```
template <typename T>
void
foo (const T &x)
{
  [&] (auto&& y)
  {
    #pragma omp parallel for
    for (auto&& [v1, v2] : x)
      ;
  } ([]{});
}

struct A { int a, b; };

void
bar ()
{
  A a[10];
  foo (a);
}
```

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator with openmp and structured bindings in a template

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Not on the trunk.  Note, the r13-4460, r13-4461, r13-5379 changes PR84469
changes weren't backported to older branches intentionally, it is quite risky
and had multiple follow-ups.

[Bug c++/105839] internal compiler error: in tsubst_omp_for_iterator with openmp and structured bindings in a template

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105839

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:f0ef740d54f47ff614eb02e13e8f4cb11dfbb140

commit r13-6407-gf0ef740d54f47ff614eb02e13e8f4cb11dfbb140
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 2 09:02:12 2023 +0100

    openmp: Fix up error recovery for invalid structured bindings in OpenMP
range for loops [PR105839]

    The PR108503 temporary DECL_HAS_VALUE_EXPR_P clearing code can ICE
    during recovery, because cp_finish_decomp when it detects errors and
    reports them clears DECL_HAS_VALUE_EXPR_P, clears DECL_VALUE_EXPR and
    sets TREE_TYPE of the structured binding vars to error_mark_node.
    The PR108503 code had an assertion that DECL_HAS_VALUE_EXPR_P is set
    so that it can clear it and restore later.

    The following patch allows DECL_HAS_VALUE_EXPR_P to be unset if
    type is error_mark_node and doesn't set it again in that case.

    2023-03-02  Jakub Jelinek  <jakub@redhat.com>

            PR c++/105839
            * parser.cc (cp_convert_omp_range_for): Allow in assert
            decomp_first_name without DECL_HAS_VALUE_EXPR_P if it has
            error_mark_node type.
            (cp_finish_omp_range_for): Don't set DECL_HAS_VALUE_EXPR_P back
            on decls which have error_mark_node type.

            * g++.dg/gomp/pr105839-1.C: New test.
            * g++.dg/gomp/pr105839-2.C: New test.