Seems that people find compile-time error on the following testcase overly pedantic. I.e. that "enum A { X = -1 << 1 };" should compile, at least with -fpermissive. So I've changed the error_at into permerror and the return value of cxx_eval_check_shift_p now depends on flag_permissive. Luckily, I didn't have to modify any of the existing tests.
Bootstrapped/regtested on x86_64-linux, ok for trunk? 2016-01-12 Marek Polacek <pola...@redhat.com> PR c++/68979 * constexpr.c (cxx_eval_check_shift_p): Use permerror rather than error_at and return negated flag_permissive. * g++.dg/warn/permissive-1.C: New test. diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c index e60180e..dbcc242 100644 --- gcc/cp/constexpr.c +++ gcc/cp/constexpr.c @@ -1512,17 +1512,17 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx, if (tree_int_cst_sgn (rhs) == -1) { if (!ctx->quiet) - error_at (loc, "right operand of shift expression %q+E is negative", - build2_loc (loc, code, type, lhs, rhs)); - return true; + permerror (loc, "right operand of shift expression %q+E is negative", + build2_loc (loc, code, type, lhs, rhs)); + return !flag_permissive; } if (compare_tree_int (rhs, uprec) >= 0) { if (!ctx->quiet) - error_at (loc, "right operand of shift expression %q+E is >= than " - "the precision of the left operand", - build2_loc (loc, code, type, lhs, rhs)); - return true; + permerror (loc, "right operand of shift expression %q+E is >= than " + "the precision of the left operand", + build2_loc (loc, code, type, lhs, rhs)); + return !flag_permissive; } /* The value of E1 << E2 is E1 left-shifted E2 bit positions; [...] @@ -1536,9 +1536,10 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx, if (tree_int_cst_sgn (lhs) == -1) { if (!ctx->quiet) - error_at (loc, "left operand of shift expression %q+E is negative", - build2_loc (loc, code, type, lhs, rhs)); - return true; + permerror (loc, + "left operand of shift expression %q+E is negative", + build2_loc (loc, code, type, lhs, rhs)); + return !flag_permissive; } /* For signed x << y the following: (unsigned) x >> ((prec (lhs) - 1) - y) @@ -1555,9 +1556,9 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx, if (tree_int_cst_lt (integer_one_node, t)) { if (!ctx->quiet) - error_at (loc, "shift expression %q+E overflows", - build2_loc (loc, code, type, lhs, rhs)); - return true; + permerror (loc, "shift expression %q+E overflows", + build2_loc (loc, code, type, lhs, rhs)); + return !flag_permissive; } } return false; diff --git gcc/testsuite/g++.dg/warn/permissive-1.C gcc/testsuite/g++.dg/warn/permissive-1.C index e69de29..7223e68 100644 --- gcc/testsuite/g++.dg/warn/permissive-1.C +++ gcc/testsuite/g++.dg/warn/permissive-1.C @@ -0,0 +1,8 @@ +// PR c++/68979 +// { dg-do compile } +// { dg-options "-fpermissive -Wno-shift-overflow -Wno-shift-count-overflow -Wno-shift-count-negative" } + +enum A { AA = -1 << 4 }; // { dg-warning "operand of shift expression" "" { target c++11 } } +enum B { BB = 1 << -4 }; // { dg-warning "operand of shift expression" } +enum C { CC = 1 << 100 }; // { dg-warning "operand of shift expression" } +enum D { DD = 31 << 30 }; // { dg-warning "shift expression" "" { target c++11 } } Marek