https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91024
Bug ID: 91024
Summary: -Wimplicit-fallthrough is confused by likely/unlikely
attributes
Product: gcc
Version: 9.1.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
int f(char c)
{
int result = 0;
switch (c)
{
case 'O':
case 'K':
return result;
[[unlikely]] case 'X':
case 'x':
return result;
default:
break;
}
return result;
}
attr.cc: In function 'int f(char)':
attr.cc:10:18: warning: this statement may fall through
[-Wimplicit-fallthrough=]
10 | [[unlikely]] case 'X':
| ^~~~
attr.cc:11:5: note: here
11 | case 'x':
| ^~~~
Without the attribute there, there's no warning about fallthrough (because the
case is empty). The attribute causes it to warn.
At a guess, the code that decides whether a case is empty should ignore
attributes in the tree.
