[Bug c/89035] Request - builtins for unspecified and arbitrary values

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89035

Eric Gallager  changed:

   What|Removed |Added

   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=91225

--- Comment #5 from Eric Gallager  ---
(In reply to Eric Gallager from comment #4)
> (In reply to David Brown from comment #2)
> > Yes, "int x = x;" does give an unspecified value without a warning.
> 
> Really, not even one from -Winit-self?

Martin Sebor explains in bug 91225 that "int x = x;" by itself is eliminated as
unused; x would have to actually be used after that to get the -Winit-self
warning.

[Bug c/89035] Request - builtins for unspecified and arbitrary values

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89035

Eric Gallager  changed:

   What|Removed |Added

 CC||egallager at gcc dot gnu.org

--- Comment #4 from Eric Gallager  ---
(In reply to David Brown from comment #2)
> Yes, "int x = x;" does give an unspecified value without a warning.

Really, not even one from -Winit-self?

[Bug c/89035] Request - builtins for unspecified and arbitrary values

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89035

Martin Sebor  changed:

   What|Removed |Added

 CC||msebor at gcc dot gnu.org

--- Comment #3 from Martin Sebor  ---
Note that an uninitialized local variable has an indeterminate value which,
even if it's not a trap representation, can appear to change from one instance
to another, and whose use results in undefined behavior (see also
https://gcc.gnu.org/ml/gcc/2019-01/msg00199.html).

[Bug c/89035] Request - builtins for unspecified and arbitrary values

[david at westcontrol dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89035

--- Comment #2 from David Brown  ---
Yes, "int x = x;" does give an unspecified value without a warning.  But to me,
this looks much more like a workaround - while "int x =
__builtin_unspecified();" is clear in its intentions.

[Bug c/89035] Request - builtins for unspecified and arbitrary values

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89035

--- Comment #1 from Marc Glisse  ---
We already have

  int x = x;

for one of those, no? Or just

  int x;

but it tends to warn.