https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95725
Bug ID: 95725
Summary: Confusing error diagnostic in an invalid template
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 test.cc, makes GCC get confused while parsing.
$cat test.cc
template <decltype(= ;
$g++-trunk -w -c test.cc
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected ‘>’ before ‘;’ token
test.cc:1:22: error: expected unqualified-id before ‘;’ token
$g++-10 -w -c test.cc
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:21: error: expected ‘)’ before ‘;’ token
1 | template <decltype(= ;
| ~ ^~
| )
test.cc:1:22: error: expected ‘>’ before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected unqualified-id before ‘;’ token
$g++-9 -w -c test.cc
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:21: error: expected ‘)’ before ‘;’ token
1 | template <decltype(= ;
| ~ ^~
| )
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:11: error: expected identifier before ‘decltype’
1 | template <decltype(= ;
| ^~~~~~~~
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:21: error: expected ‘)’ before ‘;’ token
1 | template <decltype(= ;
| ~ ^~
| )
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:20: error: expected primary-expression before ‘=’ token
1 | template <decltype(= ;
| ^
test.cc:1:22: error: expected primary-expression before ‘;’ token
1 | template <decltype(= ;
| ^
test.cc:1:11: error: expected ‘>’ before ‘decltype’
1 | template <decltype(= ;
| ^~~~~~~~
test.cc:1:22: error: expected unqualified-id before ‘;’ token
1 | template <decltype(= ;
| ^
My GCC versions are:
$g++-trunk --version
g++ (GCC) 11.0.0 20200526 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$g++-10 --version
g++-10 (Ubuntu 10.1.0-2ubuntu1~18.04) 10.1.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$g++-9 --version
g++-9 (Ubuntu 9.3.0-11ubuntu0~18.04.1) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
In conclusion, GCC might have two issues in parsing this code:
1. GCC-trunk misses "error: expected ‘)’ before ‘;’ token" message
2. GCC-9 emits too many duplicated error messages.
