[Bug c++/102479] New: segfault when deducing class template arguments for tuple with libc++-14

[Bug c++/102479] New: segfault when deducing class template arguments for tuple with libc++-14

[root.main at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

            Bug ID: 102479
           Summary: segfault when deducing class template arguments for
                    tuple with libc++-14
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: root.main at gmail dot com
  Target Milestone: ---

Created attachment 51509
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51509&action=edit
processed source code of the example file that causes the crash

The expression `std::tuple(1)` causes a segfault when using recent iterations
of libc++.

Below is a summary of the commandline output of various attributes of my
machine and the failure at the end, and attached is the processed source file.


-------------------- $ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 21.04
Release:        21.04
Codename:       hirsute
-------------------- $ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   46 bits physical, 48 bits virtual
CPU(s):                          36
On-line CPU(s) list:             0-35
Thread(s) per core:              2
Core(s) per socket:              18
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           85
Model name:                      Intel(R) Core(TM) i9-7980XE CPU @ 2.60GHz
Stepping:                        4
CPU MHz:                         1200.000
CPU max MHz:                     4500.0000
CPU min MHz:                     1200.0000
BogoMIPS:                        5199.98
Virtualization:                  VT-x
L1d cache:                       576 KiB
L1i cache:                       576 KiB
L2 cache:                        18 MiB
L3 cache:                        24.8 MiB
NUMA node0 CPU(s):               0-35
Vulnerability Itlb multihit:     KVM: Mitigation: VMX disabled
Vulnerability L1tf:              Mitigation; PTE Inversion; VMX conditional
cache flushes, SMT vulnerable
Vulnerability Mds:               Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:          Mitigation; PTI
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled
via prctl and seccomp
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and
__user pointer sanitization
Vulnerability Spectre v2:        Mitigation; Full generic retpoline, IBPB
conditional, IBRS_FW, STIBP conditional, RSB filling
Vulnerability Srbds:             Not affected
Vulnerability Tsx async abort:   Mitigation; Clear CPU buffers; SMT vulnerable
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep
mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe
syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good
nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl
vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe
popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch
cpuid_fault epb cat_l3 cdp_l3 invpcid_single pti ssbd mba ibrs ibpb stibp
tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2
smep bmi2 erms invpcid rtm cqm mpx rdt_a avx512f avx512dq rdseed adx smap
clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1
xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln
pts md_clear flush_l1d
-------------------- $ dpkg -l | grep libc++-14-dev
ii  libc++-14-dev:amd64                          
1:14~++20210915104425+934e2f695e18-1~exp1~20210915085239.659         amd64     
  LLVM C++ Standard library (development files)
-------------------- $ readlink -f /usr/include/c++/v1
/usr/lib/llvm-14/include/c++/v1
-------------------- $ dpkg -l | grep g++-11
ii  g++-11                                        11.1.0-1ubuntu1~21.04        
                                       amd64        GNU C++ compiler
-------------------- $ g++-11 --version
g++-11 (Ubuntu 11.1.0-1ubuntu1~21.04) 11.1.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-------------------- $ cat misc/scratch.cc 
#include <tuple>

int main(int, char**) {
  auto t = std::tuple(1);
  return 0;
}
-------------------- $ g++-11 -nostdinc++ -v -I /usr/include/c++/v1
-D_GNU_SOURCE misc/scratch.cc -std=c++23 -Wall -Wextra
Using built-in specs.
COLLECT_GCC=g++-11
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
11.1.0-1ubuntu1~21.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-11
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-11-RPS7jb/gcc-11-11.1.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-RPS7jb/gcc-11-11.1.0/debian/tmp-gcn/usr
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.1.0 (Ubuntu 11.1.0-1ubuntu1~21.04) 
COLLECT_GCC_OPTIONS='-nostdinc++' '-v' '-I' '/usr/include/c++/v1' '-D'
'_GNU_SOURCE' '-std=c++23' '-Wall' '-Wextra' '-shared-libgcc' '-mtune=generic'
'-march=x86-64' '-dumpdir' 'a-'
 /usr/lib/gcc/x86_64-linux-gnu/11/cc1plus -quiet -nostdinc++ -v -I
/usr/include/c++/v1 -imultiarch x86_64-linux-gnu -D_GNU_SOURCE -D _GNU_SOURCE
misc/scratch.cc -quiet -dumpdir a- -dumpbase scratch.cc -dumpbase-ext .cc
-mtune=generic -march=x86-64 -Wall -Wextra -std=c++23 -version
-fasynchronous-unwind-tables -fstack-protector-strong -Wformat-security
-fstack-clash-protection -fcf-protection -o /tmp/ccZearMr.s
GNU C++23 (Ubuntu 11.1.0-1ubuntu1~21.04) version 11.1.0 (x86_64-linux-gnu)
        compiled by GNU C version 11.1.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.0, isl version isl-0.23-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/11/include-fixed"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/v1
 /usr/lib/gcc/x86_64-linux-gnu/11/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++23 (Ubuntu 11.1.0-1ubuntu1~21.04) version 11.1.0 (x86_64-linux-gnu)
        compiled by GNU C version 11.1.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.0, isl version isl-0.23-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 97e156f48fdef8cf4439e9091bb9d73e
g++-11: internal compiler error: Segmentation fault signal terminated program
cc1plus
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-11/README.Bugs> for instructions.

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[root.main at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

--- Comment #1 from Kent Ross <root.main at gmail dot com> ---
The error also occurs in c++20 and c++17 modes.

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
                 CC|                            |ppalka at gcc dot gnu.org
   Last reconfirmed|                            |2021-09-27

--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed, not a regression AFAICT.  Reduced rejects-valid testcase:

template<class T> struct A;

template<class T>
struct tuple {
  tuple(T);

  template<template<class> class Tmpl, typename A<Tmpl<char>>::type = 0>
  tuple(Tmpl<T>);

  template<template<class> class Tmpl, typename A<Tmpl<long>>::type = 0>
  tuple(Tmpl<T>);
};

auto r = tuple(0);

We should also make sure the alias CTAD case works too:

template<class T> using const_tuple = tuple<const T>;
auto s = const_tuple(0);

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:51018dd1395c72b3681ae5f84eceb94320472922

commit r12-3906-g51018dd1395c72b3681ae5f84eceb94320472922
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Sep 27 16:01:10 2021 -0400

    c++: deduction guides and ttp rewriting [PR102479]

    The problem here is ultimately that rewrite_tparm_list when rewriting a
    TEMPLATE_TEMPLATE_PARM introduces a tree cycle in the rewritten
    ttp that structural_comptypes can't cope with.  In particular the
    DECL_TEMPLATE_PARMS of a ttp's TEMPLATE_DECL normally captures an empty
    parameter list at its own level (and so the TEMPLATE_DECL doesn't appear
    in its own DECL_TEMPLATE_PARMS), but rewrite_tparm_list ends up giving
    it a complete parameter list.  In the new testcase below, this causes
    infinite recursion from structural_comptypes when comparing Tmpl<char>
    with Tmpl<long> (where both 'Tmpl's are rewritten ttps).

    This patch fixes this by making rewrite_template_parm give a rewritten
    template template parm an empty parameter list at its own level, thereby
    avoiding the tree cycle.  Testing the alias CTAD case revealed that
    we're not setting current_template_parms in alias_ctad_tweaks, which
    this patch also fixes.

            PR c++/102479

    gcc/cp/ChangeLog:

            * pt.c (rewrite_template_parm): Handle single-level tsubst_args.
            Avoid a tree cycle when assigning the DECL_TEMPLATE_PARMS for a
            rewritten ttp.
            (alias_ctad_tweaks): Set current_template_parms accordingly.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1z/class-deduction12.C: Also test alias CTAD in the
            same way.
            * g++.dg/cpp1z/class-deduction99.C: New test.

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kimhappy at hanyang dot ac.kr

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
*** Bug 98475 has been marked as a duplicate of this bug. ***

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 12.

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dev at gutoehrlein dot eu

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 104347 has been marked as a duplicate of this bug. ***

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |a3at.mail at gmail dot com

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 105098 has been marked as a duplicate of this bug. ***

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yahan at iscas dot ac.cn

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> ---
*** Bug 105575 has been marked as a duplicate of this bug. ***

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:f705d0f2d03cc4d9f890832798b3352553f2262f

commit r11-9992-gf705d0f2d03cc4d9f890832798b3352553f2262f
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Sep 27 16:01:10 2021 -0400

    c++: deduction guides and ttp rewriting [PR102479]

    The problem here is ultimately that rewrite_tparm_list when rewriting a
    TEMPLATE_TEMPLATE_PARM introduces a tree cycle in the rewritten
    ttp that structural_comptypes can't cope with.  In particular the
    DECL_TEMPLATE_PARMS of a ttp's TEMPLATE_DECL normally captures an empty
    parameter list at its own level (and so the TEMPLATE_DECL doesn't appear
    in its own DECL_TEMPLATE_PARMS), but rewrite_tparm_list ends up giving
    it a complete parameter list.  In the new testcase below, this causes
    infinite recursion from structural_comptypes when comparing Tmpl<char>
    with Tmpl<long> (where both 'Tmpl's are rewritten ttps).

    This patch fixes this by making rewrite_template_parm give a rewritten
    template template parm an empty parameter list at its own level, thereby
    avoiding the tree cycle.  Testing the alias CTAD case revealed that
    we're not setting current_template_parms in alias_ctad_tweaks, which
    this patch also fixes.

            PR c++/102479

    gcc/cp/ChangeLog:

            * pt.c (rewrite_template_parm): Handle single-level tsubst_args.
            Avoid a tree cycle when assigning the DECL_TEMPLATE_PARMS for a
            rewritten ttp.
            (alias_ctad_tweaks): Set current_template_parms accordingly.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1z/class-deduction12.C: Also test alias CTAD in the
            same way.
            * g++.dg/cpp1z/class-deduction99.C: New test.

    (cherry picked from commit 51018dd1395c72b3681ae5f84eceb94320472922)

[Bug c++/102479] segfault when deducing class template arguments for tuple with libc++-14

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102479

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|12.0                        |11.4
                 CC|                            |jason at gcc dot gnu.org

--- Comment #10 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Now also fixed for GCC 11.4, thanks for the bug reports.