[Bug c++/126864] New: [-fcontracts] ICE in tsubst when postcondition references constexpr template function

dragon-archer at outlook dot com via Gcc-bugs <[email protected]>
Newsgroups gmane.comp.gcc.bugs
Message-ID <[email protected]/bugzilla/> 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126864

            Bug ID: 126864
           Summary: [-fcontracts] ICE in tsubst when postcondition
                    references constexpr template function
           Product: gcc
           Version: 16.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dragon-archer at outlook dot com
  Target Milestone: ---

This was first reported to MSYS2 at
https://github.com/msys2/MINGW-packages/issues/31006. It wasn't able to
generate a bug report on MSYS2 (with both 16.1.0 and 16.2.0), but it can be
reproduced on Ubuntu with GCC 16.1.0. The generated bug report on Ubuntu is
pasted below.

contract.cpp:10:17: internal compiler error: in tsubst, at cp/pt.cc:17261
   10 |     post(i: i < bar<T>())
      |                 ^~~~~~
0x17e408f internal_error(char const*, ...)
        ../../src/gcc/diagnostic-global-context.cc:787
0x17e8b76 fancy_abort(char const*, int, char const*)
        ../../src/gcc/diagnostics/context.cc:1813
0xa522c7 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../src/gcc/cp/pt.cc:17261
0x1c35403 tsubst_template_arg(tree_node*, tree_node*, int, tree_node*)
        ../../src/gcc/cp/pt.cc:13312
0x1c35403 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
        ../../src/gcc/cp/pt.cc:14697
0x1c4d027 tsubst_expr(tree_node*, tree_node*, int, tree_node*)
        ../../src/gcc/cp/pt.cc:21476
0x1c4c3d5 tsubst_expr(tree_node*, tree_node*, int, tree_node*)
        ../../src/gcc/cp/pt.cc:22235
0x1c435b6 tsubst_expr(tree_node*, tree_node*, int, tree_node*) [clone
.constprop.3]
        ../../src/gcc/cp/pt.cc:21764
0x10e6582 rebuild_postconditions(tree_node*)
        ../../src/gcc/cp/contracts.cc:2007
0x87f19a grokfndecl
        ../../src/gcc/cp/decl.cc:12663
0x19a898a grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ../../src/gcc/cp/decl.cc:16938
0x19a66e9 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ../../src/gcc/cp/decl.cc:20167
0x198fa4b cp_parser_function_definition_from_specifiers_and_declarator
        ../../src/gcc/cp/parser.cc:36031
0x198fa4b cp_parser_init_declarator
        ../../src/gcc/cp/parser.cc:26081
0x1b7f444 cp_parser_single_declaration
        ../../src/gcc/cp/parser.cc:36575
0x1b70e2c cp_parser_template_declaration_after_parameters
        ../../src/gcc/cp/parser.cc:36228
0x1b70e2c cp_parser_explicit_template_declaration
        ../../src/gcc/cp/parser.cc:36402
0x1980d7e cp_parser_declaration
        ../../src/gcc/cp/parser.cc:17632
0x2176259 cp_parser_toplevel_declaration
        ../../src/gcc/cp/parser.cc:17742
0x2176259 cp_parser_translation_unit
        ../../src/gcc/cp/parser.cc:5596
/usr/libexec/gcc/x86_64-linux-gnu/16/cc1plus -quiet -imultiarch
x86_64-linux-gnu -D_GNU_SOURCE contract.cpp -quiet -dumpdir a- -dumpbase
contract.cpp -dumpbase-ext .cpp -mtune=generic -march=x86-64-v3 -fcontracts
-freport-bug -foffload-options=-l_GCC_stdc++ -foffload-options=-l_GCC_m
-fasynchronous-unwind-tables -fstack-protector-strong -Wformat
-Wformat-security -fstack-clash-protection -fcf-protection
-fzero-init-padding-bits=all -Wbidi-chars=any -o /tmp/ccrI2Q4D.s
Please submit a full bug report, with preprocessed source.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-16/README.Bugs> for instructions.
=== BEGIN GCC DUMP ===
601: // Target: x86_64-linux-gnu
601: // Configured with: ../src/configure -v --with-pkgversion='Ubuntu
16.1.0-2ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-16/README.Bugs
--enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2,rust,cobol,algol68
--prefix=/usr --with-gcc-major-version-only --program-suffix=-16
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/libexec --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-libstdcxx-backtrace
--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-arch-64=x86-64-v3
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-16-nXyWBu/gcc-16-16.1.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-16-nXyWBu/gcc-16-16.1.0/debian/tmp-gcn/usr
--enable-offload-defaulted --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
601: // Thread model: posix
601: // Supported LTO compression algorithms: zlib zstd
601: // gcc version 16.1.0 (Ubuntu 16.1.0-2ubuntu1)
601: //
601: // contract.cpp:10:17: internal compiler error: in tsubst, at
cp/pt.cc:17261
601: //    10 |     post(i: i < bar<T>())
601: //       |                 ^~~~~~
601: // 0x17e408f internal_error(char const*, ...)
601: //         ../../src/gcc/diagnostic-global-context.cc:787
601: // 0x17e8b76 fancy_abort(char const*, int, char const*)
601: //         ../../src/gcc/diagnostics/context.cc:1813
601: // 0xa522c7 tsubst(tree_node*, tree_node*, int, tree_node*)
601: //         ../../src/gcc/cp/pt.cc:17261
601: // 0x1c35403 tsubst_template_arg(tree_node*, tree_node*, int, tree_node*)
601: //         ../../src/gcc/cp/pt.cc:13312
601: // 0x1c35403 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
601: //         ../../src/gcc/cp/pt.cc:14697
601: // 0x1c4d027 tsubst_expr(tree_node*, tree_node*, int, tree_node*)
601: //         ../../src/gcc/cp/pt.cc:21476
601: // 0x1c4c3d5 tsubst_expr(tree_node*, tree_node*, int, tree_node*)
601: //         ../../src/gcc/cp/pt.cc:22235
601: // 0x1c435b6 tsubst_expr(tree_node*, tree_node*, int, tree_node*) [clone
.constprop.3]
601: //         ../../src/gcc/cp/pt.cc:21764
601: // 0x10e6582 rebuild_postconditions(tree_node*)
601: //         ../../src/gcc/cp/contracts.cc:2007
601: // 0x87f19a grokfndecl
601: //         ../../src/gcc/cp/decl.cc:12663
601: // 0x19a898a grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
601: //         ../../src/gcc/cp/decl.cc:16938
601: // 0x19a66e9 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
601: //         ../../src/gcc/cp/decl.cc:20167
601: // 0x198fa4b cp_parser_function_definition_from_specifiers_and_declarator
601: //         ../../src/gcc/cp/parser.cc:36031
601: // 0x198fa4b cp_parser_init_declarator
601: //         ../../src/gcc/cp/parser.cc:26081
601: // 0x1b7f444 cp_parser_single_declaration
601: //         ../../src/gcc/cp/parser.cc:36575
601: // 0x1b70e2c cp_parser_template_declaration_after_parameters
601: //         ../../src/gcc/cp/parser.cc:36228
601: // 0x1b70e2c cp_parser_explicit_template_declaration
601: //         ../../src/gcc/cp/parser.cc:36402
601: // 0x1980d7e cp_parser_declaration
601: //         ../../src/gcc/cp/parser.cc:17632
601: // 0x2176259 cp_parser_toplevel_declaration
601: //         ../../src/gcc/cp/parser.cc:17742
601: // 0x2176259 cp_parser_translation_unit
601: //         ../../src/gcc/cp/parser.cc:5596
601: // -quiet -imultiarch x86_64-linux-gnu -D_GNU_SOURCE contract.cpp -quiet
-dumpdir a- -dumpbase contract.cpp -dumpbase-ext .cpp -mtune=generic
-march=x86-64-v3 -fcontracts -freport-bug -foffload-options=-l_GCC_stdc++
-foffload-options=-l_GCC_m -fasynchronous-unwind-tables
-fstack-protector-strong -Wformat -Wformat-security -fstack-clash-protection
-fcf-protection -fzero-init-padding-bits=all -Wbidi-chars=any -o -
-frandom-seed=0 -fdump-noaddr
601: // Please submit a full bug report, with preprocessed source.
601: // Please include the complete backtrace with any bug report.
601: // See <file:///usr/share/doc/gcc-16/README.Bugs> for instructions.
601:
601: // /usr/libexec/gcc/x86_64-linux-gnu/16/cc1plus -quiet -imultiarch
x86_64-linux-gnu -D_GNU_SOURCE contract.cpp -quiet -dumpdir a- -dumpbase
contract.cpp -dumpbase-ext .cpp -mtune=generic -march=x86-64-v3 -fcontracts
-freport-bug -foffload-options=-l_GCC_stdc++ -foffload-options=-l_GCC_m
-fasynchronous-unwind-tables -fstack-protector-strong -Wformat
-Wformat-security -fstack-clash-protection -fcf-protection
-fzero-init-padding-bits=all -Wbidi-chars=any -o - -frandom-seed=0
-fdump-noaddr
601:
601: # 0 "contract.cpp"
601: # 0 "<built-in>"
601: # 0 "<command-line>"
601: # 1 "/usr/include/stdc-predef.h" 1 3
601: # 0 "<command-line>" 2
601: # 1 "contract.cpp"
601:
601: template <typename T>
601: constexpr int bar()
601: {
601:     return 1;
601: }
601:
601: template <typename T>
601: constexpr int foo()
601:     post(i: i < bar<T>())
601: {
601:     return 0;
601: }
601:
601: int main() {
601:     return 0;
601: }
=== END GCC DUMP ===

Not sure whether this is a duplicate of
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125011.
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