https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86953
Bug ID: 86953
Summary: compiler crashes with constexpr operator== and
specific struct (cxx_eval_bit_field_ref, at
cp/constexpr.c:2704)
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: remi.ducceschi at gmail dot com
Target Milestone: ---
Created attachment 44538
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44538&action=edit
preprocessed file of a small test case for the constexpr crash
Hello,
I've created a small test case that produces a compiler crash. You can find
attached the preprocessed file (main.ii) made by running the following command,
with `G++ 7.3.1 20180303 (Red Hat 7.3.1-5)` on a CentOS 7 (with the
devtoolset-7 installed), but it seems to exist on the last version too (see
https://wandbox.org/permlink/zGZWdHIrRNJKfh5Z):
g++ -O3 -Wall -Wextra -o main -save-temps -v main.cpp
I give at the end of the mail the output of the command.
You can find a run on the last G++ version (9) here:
https://wandbox.org/permlink/zGZWdHIrRNJKfh5Z
-----------------------
Here is the code:
#include <iostream>
struct Bugged {
double x; bool isfreex; bool isfreey;
constexpr bool operator==(const Bugged& other) const noexcept {
return (x == other.x) && (isfreex == other.isfreex) && (isfreey ==
other.isfreey);
}
};
int main () {
std::cout << std::boolalpha << (Bugged{} == Bugged{}) << std::endl;
return 0;
}
-----------------------
The bug only appears if I enable optimization (-02 or -O3), I guess constexpr
optimization is not done otherwise.
The problem occurs on the operator==(). The compiler crashes because it can't
compute the result of the constexpr. Note that if I change the struct so it
doesn't hold booleans, but double instead, or if I remove any of the
parentheses term in the operator== function, it doesn't crash.
Note that this code compiles on MSVC 2017 and on clang 6 (though it doesn't
mean anything).
I search for a similar bug report but didn't find anything, sorry if this is a
duplicate.
-----------------------
Below the output of the command:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/rh/devtoolset-7/root/usr/libexec/gcc/x86_64-redhat-linux/7/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,lto --prefix=/opt/rh/devtoolset-7/root/usr
--mandir=/opt/rh/devtoolset-7/root/usr/share/man
--infodir=/opt/rh/devtoolset-7/root/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --enable-plugin --with-linker-hash-style=gnu
--enable-initfini-array --with-default-libstdcxx-abi=gcc4-compatible
--with-isl=/builddir/build/BUILD/gcc-7.3.1-20180303/obj-x86_64-redhat-linux/isl-install
--enable-libmpx --enable-gnu-indirect-function --with-tune=generic
--with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
gcc version 7.3.1 20180303 (Red Hat 7.3.1-5) (GCC)
COLLECT_GCC_OPTIONS='-O3' '-Wall' '-Wextra' '-o' 'main' '-save-temps' '-v'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
/opt/rh/devtoolset-7/root/usr/libexec/gcc/x86_64-redhat-linux/7/cc1plus -E
-quiet -v -D_GNU_SOURCE main.cpp -mtune=generic -march=x86-64 -Wall -Wextra -O3
-fpch-preprocess -o main.ii
ignoring nonexistent directory
"/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/include-fixed"
ignoring nonexistent directory
"/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/x86_64-redhat-linux
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/backward
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7/include
/usr/local/include
/opt/rh/devtoolset-7/root/usr/include
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-O3' '-Wall' '-Wextra' '-o' 'main' '-save-temps' '-v'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
/opt/rh/devtoolset-7/root/usr/libexec/gcc/x86_64-redhat-linux/7/cc1plus
-fpreprocessed main.ii -quiet -dumpbase main.cpp -mtune=generic -march=x86-64
-auxbase main -O3 -Wall -Wextra -version -o main.s
GNU C++14 (GCC) version 7.3.1 20180303 (Red Hat 7.3.1-5) (x86_64-redhat-linux)
compiled by GNU C version 7.3.1 20180303 (Red Hat 7.3.1-5), GMP version
6.0.0, MPFR version 3.1.1, MPC version 1.0.1, isl version isl-0.16.1-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++14 (GCC) version 7.3.1 20180303 (Red Hat 7.3.1-5) (x86_64-redhat-linux)
compiled by GNU C version 7.3.1 20180303 (Red Hat 7.3.1-5), GMP version
6.0.0, MPFR version 3.1.1, MPC version 1.0.1, isl version isl-0.16.1-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: d120f4d100e8519a845aa191e71919b8
main.cpp: In function âint main()â:
main.cpp:23:43: in constexpr expansion of
âBugged{}.Bugged::operator==(Bugged{})â
main.cpp:23:54: internal compiler error: in cxx_eval_bit_field_ref, at
cp/constexpr.c:2565
std::cout << std::boolalpha << (Bugged{} == Bugged{}) << std::endl;
^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugzilla.redhat.com/bugzilla> for instructions.
Preprocessed source stored into /tmp/ccVplEXc.out file, please attach this to
your bugreport.
