http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57199
Bug #: 57199
Summary: [4.8, 4.9] Bogus warning: iteration NNNN invokes
undefined behavior -Waggressive-loop-optimizations
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
Google ref: b/8856275
Test case:
typedef decltype(sizeof(0)) size_t;
struct Foo {
~Foo(); // comment out -> problem disappears
int x[20];
};
template <typename T, int N>
struct InlinedVector {
inline InlinedVector() : size_(0) { }
inline size_t size() const {
return size_;
}
T* mutable_array();
void resize(size_t n) {
size_t s = size();
DestroyElements(mutable_array() + n, s - n);
}
static void DestroyElements(T* ptr, size_t num) {
for (size_t i = 0; i < num; i++) {
ptr[i].~T();
}
}
size_t size_;
};
struct CP {
void Add();
InlinedVector<Foo,1> foo_;
};
void CP::Add() {
foo_.resize(foo_.size() + 1);
}
Using trunk r198689:
g++ -std=c++11 -O2 -c tt.cc
tt.cc: In member function ‘void CP::Add()’:
tt.cc:21:7: warning: iteration 230584300921369396ul invokes undefined behavior
[-Waggressive-loop-optimizations]
ptr[i].~T();
^
tt.cc:20:5: note: containing loop
for (size_t i = 0; i < num; i++) {
^
