https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94078
Bug ID: 94078
Summary: bogus and missing -Wmismatched-tags on an instance of
a template
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
The test case below shows GCC gets confused by the declarations of the template
instances below: it issues -Wmismatched-tags for the wrong declaration and
fails to diagnose the one it's supposed to, and it doesn't issue
-Wredundant-tags for either of them.
$ cat t.C && gcc -Wall -Wextra -Wmismatched-tags -Wredundant-tags -S t.C
template <class> struct S;
extern class S<int> si; // missing -Wmismatched-tags
extern struct S<int> si; // bogus -Wmismatched-tags
t.C:3:15: warning: ‘S<int>’ declared with a mismatched class-key ‘struct’
[-Wmismatched-tags]
3 | extern struct S<int> si; // bogus -Wmismatched-tags
| ^~~~~~
t.C:3:15: note: replace the class-key with ‘class’
t.C:2:14: note: ‘S<int>’ first declared as ‘class’ here
2 | extern class S<int> si; // missing -Wmismatched-tags
| ^~~~~~
Clang points out the correct declarations:
t.C:2:8: warning: class 'S' was previously declared as a struct; this is valid,
but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
extern class S<int> si; // missing -Wmismatched-tags
^
t.C:1:25: note: previous use is here
template <class> struct S;
^
