https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89616
Bug ID: 89616
Summary: Parameter names can be redeclared in outermost block
of a function definition
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jtcash at ucsd dot edu
Target Milestone: ---
Created attachment 45913
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45913&action=edit
The simplest .cpp file to experience this bug
Affected Version: All versions I've tested on multiple platforms, spanning
4.1.2 to trunk.
System Type: All platforms I've tested, including Window and Linux. Compiler
Explorer shows it exists on all versions of GCC on all architectures.
GCC Build Options: Any (details of one of the systems I tested on are provided
below)
Command to experience the bug:
$ g++ -x c++ - -c <<< 'void f(int x){ void x(); }'
Or just compile the attached example file however you want, such as:
$ g++ -c gcc_redeclaration_bug.cpp -Wall -Wextra
Expected Behavior: The compiler should fail and give an error message, as this
code is invalid C++ code according to the standard.
Actual Behavior: The code compiles fine, providing an unused parameter warning
if -Wunused-parameter is enabled.
The C++ standard states "A parameter name shall not be redeclared in the
outermost block of the function definition nor in the outermost block of any
handler associated with a function-try-block."
Additional information/examples:
Clang and MSVC both follow the standard correctly, and this bug is not present.
Here is a Compiler Explorer link which demonstrates this bug:
https://godbolt.org/z/X0ka5R
Here is an Ideone link which demonstrates this bug: https://ideone.com/fwN7nO
Here is the stackoverflow post where this bug was discovered:
https://stackoverflow.com/q/55033461/
Exact version of GCC: I'll just provide info from one of the platforms I tested
on, as it is in the bug report requirements.
$ gcc -v
Using built-in specs.
COLLECT_GCC=C:\msys64\mingw64\bin\gcc.exe
COLLECT_LTO_WRAPPER=C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.2.0/lto-wrapper.exe
Target: x86_64-w64-mingw32
Configured with: ../gcc-8.2.0/configure --prefix=/mingw64
--with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32
--host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32
--with-native-system-header-dir=/mingw64/x86_64-w64-mingw32/include
--libexecdir=/mingw64/lib --enable-bootstrap --with-arch=x86-64
--with-tune=generic --enable-languages=ada,c,lto,c++,objc,obj-c++,fortran
--enable-shared --enable-static --enable-libatomic --enable-threads=posix
--enable-graphite --enable-fully-dynamic-string
--enable-libstdcxx-filesystem-ts=yes --enable-libstdcxx-time=yes
--disable-libstdcxx-pch --disable-libstdcxx-debug --disable-isl-version-check
--enable-lto --enable-libgomp --disable-multilib --enable-checking=release
--disable-rpath --disable-win32-registry --disable-nls --disable-werror
--disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw64
--with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64
--with-pkgversion='Rev1, Built by MSYS2 project'
--with-bugurl=https://sourceforge.net/projects/msys2 --with-gnu-as
--with-gnu-ld
Thread model: posix
gcc version 8.2.0 (Rev1, Built by MSYS2 project)
