[gcc r14-9484] tree-core: clarify clobber comments

[gcc r14-9484] tree-core: clarify clobber comments

[Jason Merrill]

https://gcc.gnu.org/g:efab88888c1b692ab080bcee99a6ef7ba6ee43ed

commit r14-9484-gefab88888c1b692ab080bcee99a6ef7ba6ee43ed
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Feb 22 10:06:27 2024 +0000

    tree-core: clarify clobber comments
    
    It came up on the mailing list that OBJECT_BEGIN/END are described as
    marking object lifetime, but mark the beginning of the constructor and end
    of the destructor, whereas the C++ notion of lifetime is between the end of
    the constructor and beginning of the destructor.  So let's fix the comments.
    
    gcc/ChangeLog:
    
            * tree-core.h (enum clobber_kind): Clarify CLOBBER_OBJECT_*
            comments.

Diff:
---
 gcc/tree-core.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index d529712306d..a74fbdf75b4 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -993,9 +993,11 @@ enum clobber_kind {
   CLOBBER_UNDEF,
   /* Beginning of storage duration, e.g. malloc.  */
   CLOBBER_STORAGE_BEGIN,
-  /* Beginning of object lifetime, e.g. C++ constructor.  */
+  /* Beginning of object data, e.g. start of C++ constructor.  This differs
+     from C++ 'lifetime', which starts when initialization is complete; a
+     clobber there would discard the initialization.  */
   CLOBBER_OBJECT_BEGIN,
-  /* End of object lifetime, e.g. C++ destructor.  */
+  /* End of object data, e.g. end of C++ destructor.  */
   CLOBBER_OBJECT_END,
   /* End of storage duration, e.g. free.  */
   CLOBBER_STORAGE_END,