https://llvm.org/bugs/show_bug.cgi?id=23416
Bug ID: 23416
Summary: false positive, unused loop variable
Product: clang
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
struct range {
int start; int stop;
struct iter {
int i;
bool operator!=(iter other) { return other.i != i; };
iter& operator++() { ++i; return *this; };
int operator*() { return i; }
};
iter begin() { return iter{start}; }
iter end() { return iter{stop}; }
};
int main()
{
int power = 1;
for (int i : range{0,10})
power *= 10;
}
bug.cc:15:13: warning: unused variable 'i' [-Wunused-variable]
for (int i : range{0,10})
Manifestly, i is used to count loop iterations. The warning cannot be
suppressed by any decoration of the declaration; the best we can do is
void(i), power *= 10;
in the loop body. The warning is useful in most cases. The exception might be
that, here, the iterator has no reference or pointer members, and the loop body
changes external state.
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