http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47950
Summary: [C++0x] Internal compiler error: non-dependent declaration as condition causes tsubst_copy_and_build assertion failure. Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: dev.li...@jessamine.co.uk The following program demonstrates an assertion failure in tsubst_copy_and_build when compiling in C++0x mode. It may be related to bug 47808 which fails the same assertion via a different route (looks like it's using a non-dependent constexpr function to determine the size of an array). This issue demonstrated here appears to manifest only when a non-dependent declaration is used as a condition within a selection statement inside a template -- and only then if the standard initializer syntax is used with the rhs being a constructor or function call. This was done using 4.6.0 20110302 built this morning. Failures only occur in C++0x mode. This is a recent regression -- a build from a few days ago did not exhibit this issue. template <typename T> struct empty { // allow success case to build (not relevant to bug) operator bool() { return true; } }; template <typename T> struct from_int { from_int(int) {} // allow success case to build (not relevant to bug) operator bool() { return true; } }; template <typename T> from_int<T> via_function(T v) { return from_int<T>(v); } template <typename T> void f() { // ********* this section compiles *********** // these plain initializers work fine from_int<int> a = 7; from_int<int> b = from_int<int>(7); empty<int> c = empty<int>(); from_int<T> ta = 7; from_int<T> tb = from_int<T>(7); empty<T> tc = empty<T>(); // these dependent condition decls work fine if (empty<T> x = empty<T>()) ; if (from_int<T> x = 7) ; if (from_int<T> x = from_int<T>(7)) ; if (from_int<T> x = via_function(T())) ; // this non-dependent condition decl using conversion works fine if (from_int<int> x = 7) ; // these non-dependent condition decls using conversion or braced- // initialization work fine (in c++0x mode only course) #if __GXX_EXPERIMENTAL_CXX0X__ if (empty<int> x {}) ; if (from_int<int> x {7}) ; #endif // ********** this section fails in C++0x *********** // the following non-dependent condition decls cause an assertion // failure in // // tsubst_copy_and_build, at cp/pt.c:13370 // // in C++0x mode // if (empty<int> x = empty<int>()) ; if (from_int<int> x = from_int<int>(7)) ; if (from_int<int> x = via_function(7)) ; } int main() { f<int>(); }