https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95657
Bug ID: 95657
Summary: Bogus error message in "auto" with -std=c++11
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haoxintu at gmail dot com
Target Milestone: ---
This code bug.cc
decltype (auto) foo( decltype (auto) a ){ }
in GCC-trunk
$g++ -c -std=c++11 bug.cc
bug.cc:1:11: error: expected primary-expression before ‘auto’
1 | decltype (auto) foo( decltype (auto) a ){ }
| ^~~~
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
1 | decltype (auto) foo( decltype (auto) a ){ }
| ^~~~
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
bug.cc:1:33: error: use of ‘auto’ in parameter declaration only available with
‘-std=c++14’ or ‘-std=gnu++14’
bug.cc:1:33: error: expected primary-expression before ‘auto’
bug.cc:1:22: error: expected primary-expression before ‘decltype’
1 | decltype (auto) foo( decltype (auto) a ){ }
| ^~~~~~~~~~~~~~~~
I am sure there were some duplicate error messages about "error: use of ‘auto’
in parameter declaration only available with ‘-std=c++14’ or ‘-std=gnu++14’".
While in clang
$clang++ -c -std=c++11 bug.cc
bug.cc:1:11: warning: 'decltype(auto)' type specifier is a C++14 extension
[-Wc++14-extensions]
decltype (auto) foo( decltype (auto) a ){ }
^
bug.cc:1:33: warning: 'decltype(auto)' type specifier is a C++14 extension
[-Wc++14-extensions]
decltype (auto) foo( decltype (auto) a ){ }
^
bug.cc:1:22: error: 'decltype(auto)' not allowed in function prototype
decltype (auto) foo( decltype (auto) a ){ }
^~~~~~~~
bug.cc:1:1: error: deduced return types are a C++14 extension
decltype (auto) foo( decltype (auto) a ){ }
^
2 warnings and 2 errors generated.
