Where in C++ module streaming to handle a new bitfield added in "tree_decl_common"

[Qing Zhao <qing.zhao@oracle.com>]

Hi, Nathan,

I am adding a new bitfield “decl_not_flexarray” in “tree_decl_common”  (gcc/tree-core.h) for the new gcc feature -fstrict-flex-arrays. 

====
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index ea9f281f1cc..458c6e6ceea 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1813,7 +1813,10 @@ struct GTY(()) tree_decl_common {
     TYPE_WARN_IF_NOT_ALIGN.  */
  unsigned int warn_if_not_align : 6;

-  /* 14 bits unused.  */
+  /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY.  */
+  unsigned int decl_not_flexarray : 1;
+
+  /* 13 bits unused.  */

  /* UID for points-to sets, stable over copying from inlining.  */
  unsigned int pt_uid;
====

(Please refer to the following for details:

https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598556.html
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598965.html
)

Richard mentioned the following:

"I've not seen it so you are probably missing it - the bit has to be
streamed in tree-streamer-{in,out}.cc to be usable from LTO.  Possibly
C++ module streaming also needs to handle it.”

I have figured out that where to add the handling of the bit in “tree-streamer-{in, out}.cc,
However, it’s quite difficult for me to locate where should I add the handling of this new bit in 
C++ module streaming,  could you please help me on this?

Thanks a lot for your help.

Qing