https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61751
Bug ID: 61751 Summary: Empty brace-initializer causes double destruction of unique_ptr Product: gcc Version: 4.8.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: perso...@e-maxx.ru Created attachment 33091 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33091&action=edit Full example. Use of empty brace-initializer in default function argument causes strange effects and, finally, crashes. The minimal code is: #include <memory> class A { std::unique_ptr<int> ptr_; public: A() : ptr_(new int(123)) { } A(A&& other) : ptr_(std::move(other.ptr_)) { } }; void f(A a) { } void g(A a = {}) // replace "{}" with "A()" makes it work { f(std::move(a)); } int main() { g(); } There is a more detailed example in the attachment, which produces some debug output, e.g.: A() called [this=0x7ffffbac34f0, constructed unique_ptr=0xe18010] A(A&&) called [this=0x7ffffbac34b0, other=0x7ffffbac34d0] ~A() called [this=0x7ffffbac34b0, unique_ptr=0xe18010] ~A() called [this=0x7ffffbac34f0, unique_ptr=0xe18010] *** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0000000000e18010 *** On the contrary, using some correct version of compiler (I tried 4.6.3 and 4.9.0) we get: A() called [this=0x7fff77c52810, constructed unique_ptr=0xe1c010] A(A&&) called [this=0x7fff77c527e0, other=0x7fff77c52810] ~A() called [this=0x7fff77c527e0, unique_ptr=0xe1c010] ~A() called [this=0x7fff77c52810, unique_ptr=0] As it can be seen, the difference is that the bogus version moves from object that has never been constructed.