On 5/29/20 6:25 AM, Jakub Jelinek wrote:
Hi!cxx_eval_outermost_constant_expr had a check for reinterpret_casts from pointers (well, it checked from ADDR_EXPRs) to integral type, but that only caught such cases at the toplevel of expressions. As the comment said, it should be done even inside of the expressions, but at the point of the writing e.g. pointer differences used to be a problem. We now have POINTER_DIFF_EXPR, so this is no longer an issue. Had to do it just for CONVERT_EXPR, because the FE emits NOP_EXPR casts from pointers to integrals in various spots, e.g. for the PMR & 1 tests, though on NOP_EXPR we have the REINTERPRET_CAST_P bit that we do check, while on CONVERT_EXPR we don't. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? PR92411 is not fixed by this change though. 2020-05-29 Jakub Jelinek <ja...@redhat.com> PR c++/82304 PR c++/95307 * constexpr.c (cxx_eval_constant_expression): Diagnose CONVERT_EXPR conversions from pointer types to arithmetic types here... (cxx_eval_outermost_constant_expr): ... instead of here. * g++.dg/template/pr79650.C: Expect different diagnostics and expect it on all lines that do pointer to integer casts. * g++.dg/cpp1y/constexpr-shift1.C: Expect different diagnostics. * g++.dg/cpp1y/constexpr-82304.C: New test. * g++.dg/cpp0x/constexpr-95307.C: New test. --- gcc/cp/constexpr.c.jj 2020-05-28 23:12:19.715303826 +0200 +++ gcc/cp/constexpr.c 2020-05-29 12:02:06.161656532 +0200 @@ -6194,6 +6194,18 @@ cxx_eval_constant_expression (const cons if (VOID_TYPE_P (type)) return void_node;+ if (TREE_CODE (t) == CONVERT_EXPR+ && ARITHMETIC_TYPE_P (type) + && INDIRECT_TYPE_P (TREE_TYPE (op))) + { + if (!ctx->quiet) + error ("conversion from pointer type %qT " + "to arithmetic type %qT in a constant expression", + TREE_TYPE (op), type); + *non_constant_p = true; + return t; + } + if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type)) op = cplus_expand_constant (op);@@ -6795,19 +6807,6 @@ cxx_eval_outermost_constant_expr (tree tnon_constant_p = true; }- /* Technically we should check this for all subexpressions, but that- runs into problems with our internal representation of pointer - subtraction and the 5.19 rules are still in flux. */ - if (CONVERT_EXPR_CODE_P (TREE_CODE (r)) - && ARITHMETIC_TYPE_P (TREE_TYPE (r)) - && TREE_CODE (TREE_OPERAND (r, 0)) == ADDR_EXPR) - { - if (!allow_non_constant) - error ("conversion from pointer type %qT " - "to arithmetic type %qT in a constant expression", - TREE_TYPE (TREE_OPERAND (r, 0)), TREE_TYPE (r)); - non_constant_p = true; - }if (!non_constant_p && overflow_p)non_constant_p = true; --- gcc/testsuite/g++.dg/template/pr79650.C.jj 2020-01-12 11:54:37.249400796 +0100 +++ gcc/testsuite/g++.dg/template/pr79650.C 2020-05-29 12:02:06.180656252 +0200 @@ -11,10 +11,10 @@ foo () static int a, b; lab1: lab2: - A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab2> c; // { dg-error "not a constant integer" } - A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab1> d; - A<(intptr_t)&a - (intptr_t)&b> e; // { dg-error "is not a constant expression" } - A<(intptr_t)&a - (intptr_t)&a> f; - A<(intptr_t)sizeof(a) + (intptr_t)&a> g; // { dg-error "not a constant integer" } + A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab2> c; // { dg-error "conversion from pointer type" } + A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab1> d; // { dg-error "conversion from pointer type" } + A<(intptr_t)&a - (intptr_t)&b> e; // { dg-error "conversion from pointer type" } + A<(intptr_t)&a - (intptr_t)&a> f; // { dg-error "conversion from pointer type" } + A<(intptr_t)sizeof(a) + (intptr_t)&a> g; // { dg-error "conversion from pointer type" } A<(intptr_t)&a> h; // { dg-error "conversion from pointer type" } } --- gcc/testsuite/g++.dg/cpp1y/constexpr-shift1.C.jj 2020-01-12 11:54:37.115402818 +0100 +++ gcc/testsuite/g++.dg/cpp1y/constexpr-shift1.C 2020-05-29 12:02:06.180656252 +0200 @@ -3,7 +3,8 @@ constexpr int p = 1; constexpr __PTRDIFF_TYPE__ bar (int a) { - return ((__PTRDIFF_TYPE__) &p) << a; // { dg-error "is not a constant expression" } + return ((__PTRDIFF_TYPE__) &p) << a; } constexpr __PTRDIFF_TYPE__ r = bar (2); // { dg-message "in .constexpr. expansion of" } + // { dg-error "conversion from pointer" "" { target *-*-* } .-1 } constexpr __PTRDIFF_TYPE__ s = bar (0); // { dg-error "conversion from pointer" }
This is a diagnostic quality regression, moving the error message away from the line where the actual problem is.
Maybe use error_at (loc, ...)? Jason
