Message ID | 51913E17.4050000@redhat.com |
---|---|
State | New |
Headers | show |
On Mon, May 13, 2013 at 03:25:11PM -0400, Jason Merrill wrote: > In this testcase, since one of the overloads takes a pointer, we > need to check whether the argument is a valid null pointer constant. > In C++11 only an integer literal can be a null pointer constant of > integral type, but in C++03 we need to handle other integer constant > expressions. Here we were passing the call expression into > value_dependent_expression_p, but in C++03 mode that function > expects its argument to be a constant expression, and the expression > wasn't filtered out by potential_constant_expression. The simplest > solution is to just check TREE_SIDE_EFFECTS since in C++03 mode an > expression with side-effects can't be a constant expression (unlike > in C++11, where constexpr function substitution can produce a > constant expression from one with TREE_SIDE_EFFECTS). What about the 4 other maybe_constant_value on fold_non_dependent_expr_sfinae (something, tf_none) calls in typeck.c (two for -Wdiv-by-zero and two for shift diagnostics)? Should that be if (cxx_dialect >= cxx0x || !TREE_SIDE_EFFECTS (t)) guarded (or wrapped into some helper function that will do all of tree some_good_name (tree t) { if (cxx_dialect < cxx0x && TREE_SIDE_EFFECTS (t)) return t; t = fold_non_dependent_expr_sfinae (t, tf_none); return maybe_constant_value (t); } Plus there is one guarded by ENABLE_CHECKING in pt.c. Jakub
commit bd25166552f6aa94b8da3ffea0201213e8057b17 Author: Jason Merrill <jason@redhat.com> Date: Mon May 13 13:34:31 2013 -0400 PR c++/56998 * call.c (null_ptr_cst_p): An expression with side-effects can't be a C++03 null pointer constant. diff --git a/gcc/cp/call.c b/gcc/cp/call.c index bd8f531..9f3a50d 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -554,7 +554,7 @@ null_ptr_cst_p (tree t) if (CP_INTEGRAL_TYPE_P (TREE_TYPE (t))) { /* Core issue 903 says only literal 0 is a null pointer constant. */ - if (cxx_dialect < cxx0x) + if (cxx_dialect < cxx0x && !TREE_SIDE_EFFECTS (t)) t = maybe_constant_value (fold_non_dependent_expr_sfinae (t, tf_none)); STRIP_NOPS (t); if (integer_zerop (t) && !TREE_OVERFLOW (t)) diff --git a/gcc/testsuite/g++.dg/template/overload13.C b/gcc/testsuite/g++.dg/template/overload13.C new file mode 100644 index 0000000..d41ccd0 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/overload13.C @@ -0,0 +1,16 @@ +// PR c++/56998 + +class Secret; +char IsNullLiteralHelper(Secret* p); +char (&IsNullLiteralHelper(...))[2]; + +struct C +{ + int val() { return 42; } +}; + +template <typename T> +unsigned f() +{ + return sizeof(IsNullLiteralHelper(C().val())); +}