https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69327
Bug ID: 69327
Summary: constexpr leaves reference member var uninitialized
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sbergman at redhat dot com
Target Milestone: ---
With recent trunk GCC,
> $ cat test.cc
> struct S {
> constexpr S(int & x): n(x) {}
> int & n;
> };
> constexpr S f1(int & x) { return S(x); }
> constexpr S f2(int & x) { return f1(x); }
> S f3(int & x) { return f2(x); }
> int main() {
> int n = 1;
> return f3(n).n;
> }
> $ g++ test.cc && ./a.out
> Segmentation fault
typically causes a SEGV, as S::n remains uninitialized; x86-64 code generated
for f3 is
> 0000000000000000 <_Z2f3Ri>:
> 0: 55 push %rbp
> 1: 48 89 e5 mov %rsp,%rbp
> 4: 48 89 7d e8 mov %rdi,-0x18(%rbp)
> 8: 48 8b 45 f8 mov -0x8(%rbp),%rax
> c: 5d pop %rbp
> d: c3 retq
This is a stripped-down version of code in boost::fusion (calling
boost::fusion::begin on a boost::fusion::cons, as used by boost::spirit, in
turn used by libetonyek and LibreOffice), causing LibreOffice to fail.
