https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88504
Bug ID: 88504
Summary: Inconsistent error message notes when using
forward-declared type as value
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: petschy at gmail dot com
Target Milestone: ---
struct Foo;
struct Bar
{
Bar(Foo f_) :
m_foo(f_)
{
}
Foo m_foo;
};
Foo baz1()
{
}
void baz2(Foo f_)
{
}
void baz3()
{
Foo foo;
}
Foo g_foo;
$ g++-9.0.0 -Wall -Wextra -c 20181214-fwddecl_value.cpp
20181214-fwddecl_value.cpp:10:6: error: field ‘m_foo’ has incomplete type ‘Foo’
10 | Foo m_foo;
| ^~~~~
20181214-fwddecl_value.cpp:1:8: note: forward declaration of ‘struct Foo’
1 | struct Foo;
| ^~~
20181214-fwddecl_value.cpp:5:10: error: ‘f_’ has incomplete type
5 | Bar(Foo f_) :
| ~~~~^~
20181214-fwddecl_value.cpp:1:8: note: forward declaration of ‘struct Foo’
1 | struct Foo;
| ^~~
20181214-fwddecl_value.cpp:13:10: error: return type ‘struct Foo’ is incomplete
13 | Foo baz1()
| ^
20181214-fwddecl_value.cpp:17:15: error: ‘f_’ has incomplete type
17 | void baz2(Foo f_)
| ~~~~^~
20181214-fwddecl_value.cpp:1:8: note: forward declaration of ‘struct Foo’
1 | struct Foo;
| ^~~
20181214-fwddecl_value.cpp: In function ‘void baz2(Foo)’:
20181214-fwddecl_value.cpp:17:15: warning: unused parameter ‘f_’
[-Wunused-parameter]
17 | void baz2(Foo f_)
| ~~~~^~
20181214-fwddecl_value.cpp: In function ‘void baz3()’:
20181214-fwddecl_value.cpp:23:6: error: aggregate ‘Foo foo’ has incomplete type
and cannot be defined
23 | Foo foo;
| ^~~
20181214-fwddecl_value.cpp: At global scope:
20181214-fwddecl_value.cpp:26:5: error: aggregate ‘Foo g_foo’ has incomplete
type and cannot be defined
26 | Foo g_foo;
| ^~~~~
Most messages contain the note where the forward decl occured, but some don't:
- returning from baz1()
- local variable 'foo' in baz3()
- global variable 'g_foo'
Mentioning it everywhere would be helpful.
Quite a minor issue, but the wording of the error messages also varies
somewhat:
- inside the class: field ‘m_foo’ has incomplete type ‘Foo’
- as fn param, the name of the type is omitted : ‘f_’ has incomplete type
- when returning, 'struct Foo' is mentioned: return type ‘struct Foo’ is
incomplete
- but when defining a variable, Foo is not a struct, but an aggregate:
aggregate ‘Foo foo’ has incomplete type and cannot be defined
