diff options
Diffstat (limited to 'gcc/cp/constexpr.c')
| -rw-r--r-- | gcc/cp/constexpr.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index 7772fe6..0c2498a 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -6075,6 +6075,37 @@ inline_asm_in_constexpr_error (location_t loc) "%<constexpr%> function in C++20"); } +/* We're getting the constant value of DECL in a manifestly constant-evaluated + context; maybe complain about that. */ + +static void +maybe_warn_about_constant_value (location_t loc, tree decl) +{ + static bool explained = false; + if (cxx_dialect >= cxx17 + && warn_interference_size + && !global_options_set.x_param_destruct_interfere_size + && DECL_CONTEXT (decl) == std_node + && id_equal (DECL_NAME (decl), "hardware_destructive_interference_size") + && (LOCATION_FILE (input_location) != main_input_filename + || module_exporting_p ()) + && warning_at (loc, OPT_Winterference_size, "use of %qD", decl) + && !explained) + { + explained = true; + inform (loc, "its value can vary between compiler versions or " + "with different %<-mtune%> or %<-mcpu%> flags"); + inform (loc, "if this use is part of a public ABI, change it to " + "instead use a constant variable you define"); + inform (loc, "the default value for the current CPU tuning " + "is %d bytes", param_destruct_interfere_size); + inform (loc, "you can stabilize this value with %<--param " + "hardware_destructive_interference_size=%d%>, or disable " + "this warning with %<-Wno-interference-size%>", + param_destruct_interfere_size); + } +} + /* Attempt to reduce the expression T to a constant value. On failure, issue diagnostic and return error_mark_node. */ /* FIXME unify with c_fully_fold */ @@ -6219,6 +6250,8 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, r = *p; break; } + if (ctx->manifestly_const_eval) + maybe_warn_about_constant_value (loc, t); if (COMPLETE_TYPE_P (TREE_TYPE (t)) && is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) { |