c++: mark short-enums as packed

Unlike C, C++ doesn't mark enums shortened by -fshort-enums as packed.
This makes for undesirable warning differences between C and C++,
e.g. c-c++-common/analyzer/null-deref-pr108251-smp_fetch_ssl_fc_has_early*.c
triggers a warning about a type cast from a pointer to enum that, when
packed, might not be sufficiently aligned.

This change is not enough for that warning to trigger.  The tree
expression generated by the C++ front-end is also a little too
complicated for us get to the base pointer.  A separate patch takes
care of that.

for  gcc/cp/ChangeLog

	* decl.cc (finish_enum_value_list): Set TYPE_PACKED if
	use_short_enum, and propagate it to variants.

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index bce806819d50875be3166cca83d0709aa05f46dd..2f2dbb8d107239108ed5f08ffdb2e796d3238abe 100644 (file)
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -16913,6 +16913,12 @@ finish_enum_value_list (tree enumtype)
       /* If -fstrict-enums, still constrain TYPE_MIN/MAX_VALUE.  */
       if (flag_strict_enums)
        set_min_and_max_values_for_integral_type (enumtype, precision, sgn);
+
+      if (use_short_enum)
+       {
+         TYPE_PACKED (enumtype) = use_short_enum;
+         fixup_attribute_variants (enumtype);
+       }
     }
   else
     underlying_type = ENUM_UNDERLYING_TYPE (enumtype);