https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86564
Bug ID: 86564
Summary: Declaration containing qualified-id interpreted as
function-style cast
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zhonghao at pku dot org.cn
Target Milestone: ---
The code is as follow:
struct foo {
static bool const value = false;
};
int main() {
int v(int(foo::value));
}
g++ accepts it, but clang++ rejects it:
code0.cpp:6:17: error: parameter declarator cannot be qualified
int v(int(foo::value));
~~~~~^
code0.cpp:6:7: warning: parentheses were disambiguated as a function
declaration [-Wvexing-parse]
int v(int(foo::value));
^~~~~~~~~~~~~~~~~
code0.cpp:6:8: note: add a pair of parentheses to declare a variable
int v(int(foo::value));
^
( )
1 warning and 1 error generated.
The paragraphs in the C++ Standard, 6.8 and 8.2 say that disambiguation is
purely syntactic, and any construct that could be a declaration is taken and
parsed as a declaration. The grammar of C++ allows a declarator-id be a
qualified-id, which makes for the following be a well-formed construct
struct foo {
static int value;
};
int (foo::value);
Thus, the function declaration in main above would contain a parameter whose
name is a qualified-id. This is ill-formed and should be rejected.
