[Bug c++/115952] New: g++ 14.1.0 internal compiler error for ambiguous function template overloads

[aslobodkins at mail dot smu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115952

            Bug ID: 115952
           Summary: g++ 14.1.0 internal compiler error for ambiguous
                    function template overloads
           Product: gcc
           Version: 14.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: aslobodkins at mail dot smu.edu
  Target Milestone: ---

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I am using g++ 14.1.0 on Ubunutu 22.04 and encountered internal compiler error
when working on one of my recent projects. The function call is ambiguous and
compiler should issue a corresponding error message. Instead, the output is as
follows:


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slobod@LinuxHPC:~/Documents/Research/strict-lib/example$ make example2
g++-14.1 -std=c++20 -DSTRICT_DEBUG_OFF example2.cpp -o example2.x -lm -I
../src/
example2.cpp: In function ‘int main()’:
example2.cpp:11:29: internal compiler error: Segmentation fault
   11 |    Z(place::all, place::all)(0, 0);
      |    ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
0x742a4804251f ???
        ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
0x742a48029d8f __libc_start_call_main
        ../sysdeps/nptl/libc_start_call_main.h:58
0x742a48029e3f __libc_start_main_impl
        ../csu/libc-start.c:392
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
make: *** [Makefile:32: example2] Error 1


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Other compilers, such as 18.1.3 or g++ 13.2.0 report the error properly as
follows:


*****************************************************************************
clang++ -std=c++20 -DSTRICT_DEBUG_OFF example2.cpp -o example2.x -lm -I ../src/
example2.cpp:11:4: error: call to object of type
'Derived2D<ConstSliceArrayBase2D<ThisType>>' (aka
'Derived2D<ConstSliceArrayBase2D<Derived2D<slib::ArrayBase2D<double>>>>') is
ambiguous
   11 |    Z(place::all, place::all)(0, 0);
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~
../src/derived2D.hpp:70:53: note: candidate function [with I1 = int, I2 = int]
   70 |    STRICT_NODISCARD_CONSTEXPR_INLINE decltype(auto) operator()(I1 i, I2
j);
      |                                                     ^
../src/derived2D.hpp:247:36: note: candidate function [with S1 = int, S2 = int]
  247 |    STRICT_NODISCARD_CONSTEXPR auto operator()(S1 s1, S2 s2) &&
      |                                    ^
1 error generated.
make: *** [Makefile:32: example2] Error 1


*****************************************************************************
slobod@LinuxHPC:~/Documents/Research/strict-lib/example$ make example2
g++-13.2 -std=c++20 -DSTRICT_DEBUG_OFF example2.cpp -o example2.x -lm -I
../src/
example2.cpp: In function ‘int main()’:
example2.cpp:11:29: error: call of
‘(slib::Derived2D<slib::ConstSliceArrayBase2D<slib::Derived2D<slib::ArrayBase2D<double>
> > >) (int, int)’ is ambiguous
   11 |    Z(place::all, place::all)(0, 0);
      |    ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
In file included from ../src/array_IO.hpp:13,
                 from ../src/strict_lib.hpp:10,
                 from example2.cpp:2:
../src/derived2D.hpp:357:50: note: candidate: ‘constexpr decltype(auto)
slib::Derived2D<Base>::operator()(I1, I2) [with I1 = int; I2 = int; Base =
slib::ConstSliceArrayBase2D<slib::Derived2D<slib::ArrayBase2D<double> > >]’
  357 | STRICT_NODISCARD_CONSTEXPR_INLINE decltype(auto)
Derived2D<Base>::operator()(I1 i, I2 j) {
      |                                                  ^~~~~~~~~~~~~~~
../src/derived2D.hpp:366:50: note: candidate: ‘constexpr decltype(auto)
slib::Derived2D<Base>::operator()(I1, I2) const [with I1 = int; I2 = int; Base
= slib::ConstSliceArrayBase2D<slib::Derived2D<slib::ArrayBase2D<double> > >]’
  366 | STRICT_NODISCARD_CONSTEXPR_INLINE decltype(auto)
Derived2D<Base>::operator()(I1 i, I2 j) const {
      |                                                  ^~~~~~~~~~~~~~~
../src/derived2D.hpp:830:33: note: candidate: ‘constexpr auto
slib::Derived2D<Base>::operator()(S1, S2) const & [with S1 = int; S2 = int;
Base = slib::ConstSliceArrayBase2D<slib::Derived2D<slib::ArrayBase2D<double> >
>]’
  830 | STRICT_NODISCARD_CONSTEXPR auto Derived2D<Base>::operator()(S1 s1, S2
s2) const& {
      |                                 ^~~~~~~~~~~~~~~
../src/derived2D.hpp:863:33: note: candidate: ‘constexpr auto
slib::Derived2D<Base>::operator()(S1, S2) && requires
!(ArrayTwoDimType<slib::Derived2D<Base> >) [with S1 = int; S2 = int; Base =
slib::ConstSliceArrayBase2D<slib::Derived2D<slib::ArrayBase2D<double> > >]’
  863 | STRICT_NODISCARD_CONSTEXPR auto Derived2D<Base>::operator()(S1 s1, S2
s2) &&
      |                                 ^~~~~~~~~~~~~~~
make: *** [Makefile:32: example2] Error 1



*****************************************************************************
I have attached preprocessed file by adding save-temps option to Makefile.
Compiler configuration settings were: 

../gcc-releases-gcc-14.1.0/configure -v --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--prefix=/usr/local/gcc-14.1.0 --enable-checking=release
--enable-languages=c,c++,fortran --disable-multilib --program-suffix=-14.1