https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79301
Bug ID: 79301
Summary: With -Werror=pedantic outside C++17 mode,
__has_cpp_attribute(fallthrough) is nonzero but
[[fallthrough]] fails
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: andersk at mit dot edu
Target Milestone: ---
One would expect code like this to silence the new -Wimplicit-fallthrough
warning that’s been added to -Wextra:
switch (x) {
case 0:
printf("zero\n");
#if __has_cpp_attribute(fallthrough)
[[fallthrough]];
#elif __has_cpp_attribute(gnu::fallthrough)
[[gnu::falthrough]];
#endif
case 1:
printf("zero or one\n");
}
However, this fails to compile with -Werror=pedantic in C++14 mode or earlier:
“error: ‘fallthrough’ is a C++17 feature; use ‘gnu::fallthrough’
[-Werror=pedantic]”.
__has_cpp_attribute(fallthrough) should evaluate to 0 if [[fallthrough]] is not
going to work.
