On 05/23/2011 05:04 PM, Nathan Froyd wrote: > On 05/22/2011 02:24 PM, Tom de Vries wrote: >> Now that struct tree_type does not exist anymore, 'sizeof (struct tree_type)' >> generates an error in the following assert in fold_checksum_tree: >> ... >> gcc_assert ((sizeof (struct tree_exp) + 5 * sizeof (tree) >> <= sizeof (struct tree_function_decl)) >> && sizeof (struct tree_type) <= sizeof (struct >> tree_function_decl)); >> ... >> >> This error is triggered with -enable-checking=fold. > > Doh. Thanks for the report. > > The easy fix is s/tree_type/tree_type_non_common/. But I don't see why the > assert has to even care about tree_type; doesn't: > > gcc_assert ((sizeof (struct tree_exp) + 5 * sizeof (tree) > <= sizeof (union tree_node)); > > accomplish the same thing? > > -Nathan > >
I don't know for sure what the assert is trying to check, but I'm guessing it's trying to check that the memcpys are save. A naive implementation would be: Index: fold-const.c =================================================================== --- fold-const.c (revision 173703) +++ fold-const.c (working copy) @@ -13792,6 +13789,7 @@ recursive_label: && DECL_ASSEMBLER_NAME_SET_P (expr)) { /* Allow DECL_ASSEMBLER_NAME to be modified. */ + gcc_assert (tree_size (expr) <= sizeof (buf)); memcpy ((char *) &buf, expr, tree_size (expr)); SET_DECL_ASSEMBLER_NAME ((tree)&buf, NULL); expr = (tree) &buf; @@ -13805,6 +13803,7 @@ recursive_label: { /* Allow these fields to be modified. */ tree tmp; + gcc_assert (tree_size (expr) <= sizeof (buf)); memcpy ((char *) &buf, expr, tree_size (expr)); expr = tmp = (tree) &buf; TYPE_CONTAINS_PLACEHOLDER_INTERNAL (tmp) = 0; But that turns it into a runtime check. On the other hand, I'm not sure the original assert still makes sense. Neither tcc_type nor tcc_declaration have variable size, so the '5 * sizeof (tree)' does not seem applicable anymore. If we want checks cheaper than the naive, but more maintainable than the current, we would want something like: + gcc_assert (tree_class_max_size (tcc_declaration) <= sizeof (buf)); + gcc_assert (tree_class_max_size (tcc_type) <= sizeof (buf)); We would want those checks moved out of the hot path, and we would need to implement and maintain tree_class_max_size alongside tree_size and tree_code_size. But I'm not sure it's worth the effort. Thanks, - Tom