| Message ID | 3368547.iIbC2pHGDl@fomalhaut |
|---|---|
| State | New |
| Headers | show |
| Series | [C] Warn on type punning that toggles scalar storage order | expand |
On 5/26/2021 8:12 AM, Eric Botcazou wrote: > Hi, > > As documented in the manual, we do not support type punning that toggles the > scalar storage order, so this adds a warning for the simple case of unions. > > Tested on x86-64/Linux, OK for the mainline? > > > 2021-05-26 Eric Botcazou <ebotcazou@adacore.com> > > PR c/100653 > * c-decl.c (finish_struct): Warn for a union containing an aggregate > field with a differing scalar storage order. > > > 2021-05-26 Eric Botcazou <ebotcazou@adacore.com> > > * gcc.dg/sso-13.c: New test. OK jeff
> OK
Thanks. I have also installed the attached tweak to the documentation.
PR c/100653
* doc/extend.texi (scalar_storage_order): Rephrase slightly.
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c index 53b2b5b637d..3c7b306809d 100644 --- a/gcc/c/c-decl.c +++ b/gcc/c/c-decl.c @@ -8853,6 +8853,13 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, = c_build_qualified_type (fmain_type, TYPE_QUALS (ftype)); } } + + if (TREE_CODE (t) == UNION_TYPE + && AGGREGATE_TYPE_P (TREE_TYPE (field)) + && TYPE_REVERSE_STORAGE_ORDER (t) + != TYPE_REVERSE_STORAGE_ORDER (TREE_TYPE (field))) + warning_at (DECL_SOURCE_LOCATION (field), OPT_Wscalar_storage_order, + "type punning toggles scalar storage order"); } /* Now we have the truly final field list.