https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121221
Bug ID: 121221
Summary: array subscript 'int (**)(...)[0]' is partly outside
array bounds of 'f(bool)::A [1]'
[-Werror=array-bounds=]
Product: gcc
Version: 15.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: michaelkinrosslim at gmail dot com
Target Milestone: ---
Created attachment 61943
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61943&action=edit
The preprocessed file
gcc -v:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/15.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,m2,objc,obj-c++,rust,cobol
--enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues
--with-build-config=bootstrap-lto --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-libstdcxx-backtrace --enable-link-serialization=1
--enable-linker-build-id --enable-lto --enable-multilib --enable-plugin
--enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.1.1 20250425 (GCC)
Command used:
g++ main.cpp -o bin.out -D_GLIBCXX_ASSERTIONS --std=c++23 -O3 -pedantic -Wall
-Werror -Wextra -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations
This yields:
In lambda function,
inlined from ‘int f(bool)’ at main.cpp:17:13:
main.cpp:14:36: error: array subscript ‘int (**)(...)[0]’ is partly outside
array bounds of ‘f(bool)::A [1]’ [-Werror=array-bounds=]
14 | return (a.*member_function)();
| ~~~~~~~~~~~~~~~~~~~~^~
main.cpp: In function ‘int f(bool)’:
main.cpp:9:7: note: object ‘a’ of size 1
9 | } a;
| ^
cc1plus: all warnings being treated as errors
The code to reproduce this can be found here https://godbolt.org/z/h9h8qG9d8.
Observations:
Changing to value capture stops the warning.
Moving the variable 'a' into the lambda stops the warning, however also using
std::invoke instead of (a.*member_function)() triggers the warning again.
Passing relative_diagonal as a parameter instead of a capture also stops the
error.
Changing optimization level to O1 stops the warning.
Replacing the ternary with &A::fun stops the warning.
