https://bugs.llvm.org/show_bug.cgi?id=49458
Bug ID: 49458
Summary: Incorrect initialization of static data members in
recursive class templates
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected]
When the following code is compiled with Clang and run, it produces an
assertion failure:
$ cat test.cpp
#include <assert.h>
template <int x, int y>
struct GCD {
static int value;
};
template <int x, int y>
int GCD<x, y>::value = GCD<y, x % y>::value;
template<int x>
struct GCD<x, 0> {
static int value;
};
template<int x>
int GCD<x, 0>::value = x;
int main() {
assert((GCD<9, 6>::value) == 3);
}
$ clang test.cpp
$ ./a.out
a.out: test.cpp:20: int main(): Assertion `(GCD<9, 6>::value) == 3' failed.
Aborted (core dumped)
>From the generated LLVM IR it is clear that GCD<3, 0>::value is initialized in
the data section, whereas GCD<9, 6>::value and GCD<6, 3>::value initially have
value zero and are initialized at run time. The order of initialization however
is incorrect (according to my understanding of
http://eel.is/c++draft/temp.point#4), as if was performed using the following
code:
GCD<9, 6>::value = GCD<6, 3>::value;
GCD<6, 3>::value = GCD<3, 0>::value;
The program works as expected when compiled with GCC.
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