[Bug tree-optimization/80794] constant objects can be assumed to be immutable

[Bug tree-optimization/80794] constant objects can be assumed to be immutable

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matthijs at stdin dot nl

--- Comment #8 from Martin Sebor <msebor at gcc dot gnu.org> ---
*** Bug 96996 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/80794] constant objects can be assumed to be immutable

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=90404,
                   |                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=86318

--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> ---
See also pr86318 and especially pr90404.  As noted in c#2 on the former,
issuing a warning when an attempt is detected to modify a const object (or
subobject) as requested in pr90404 should help detect changes, resulting from
the optimization, to the behavior of code that deliberately violates the
restriction to modify constant subobjects.

[Bug tree-optimization/80794] constant objects can be assumed to be immutable

[matthijs at stdin dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794

--- Comment #10 from Matthijs Kooijman <matthijs at stdin dot nl> ---
Also note that pr96996, that was marked as a duplicate of this report, talks
about a notable subcase of the case presented in this report. While this report
talks about constant complete objects (e.g. a variable marked const), pr96996
talks about const subobjects (e.g. a const member of a variable that might not
be const itself).

That pr has some motivation to argue that such const subobjects can be
optimized in the same way as const complete objects. Maybe this is obvious for
seasoned gcc devs, but I wanted to point it out regardless, since the cases
seem distinct enough to me that one might end up fixing this for objects and
forgetting about subobjects :-)