https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116385
Bug ID: 116385
Summary: Unevaluated usage of function parameters with typeid
incorrectly considered odr-use
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mital at mitalashok dot co.uk
Target Milestone: ---
This is the example taken from https://eel.is/c++draft/basic.def.odr#example-2
but modified to use `typeid` instead of `=` to make it a non-odr-use (as the
typeid of a glvalue of a non-polymorphic type)
https://godbolt.org/z/dh6P8q4fh
```
namespace std { struct type_info; }
void f(int n) {
[] { typeid(n); };
struct A {
void f() { typeid(n); }
};
void g(const std::type_info& = typeid(n));
[](const std::type_info& = typeid(n)) {};
}
```
All 4 usages have an error.
<source>: In lambda function:
<source>:3:15: error: 'n' is not captured
3 | [] { typeid(n); };
| ^
<source>:3:4: note: the lambda has no capture-default
3 | [] { typeid(n); };
| ^
<source>:2:12: note: 'int n' declared here
2 | void f(int n) {
| ~~~~^
<source>: In member function 'void f(int)::A::f()':
<source>:5:23: error: use of parameter from containing function
5 | void f() { typeid(n); }
| ^
<source>:2:12: note: 'int n' declared here
2 | void f(int n) {
| ~~~~^
<source>: In function 'void f(int)':
<source>:7:41: error: parameter 'n' may not appear in this context
7 | void g(const std::type_info& = typeid(n));
| ^
<source>:8:37: error: parameter 'n' may not appear in this context
8 | [](const std::type_info& = typeid(n)) {};
| ^
Unevaluated usages with `sizeof` (<https://godbolt.org/z/W81ajKsbn>) do not
error
