* [Bug c++/41425] switch with enums doesn't work
2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
@ 2009-09-21 12:19 ` Woebbeking at web dot de
2009-09-21 12:21 ` Woebbeking at web dot de
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From: Woebbeking at web dot de @ 2009-09-21 12:19 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from Woebbeking at web dot de 2009-09-21 12:19 -------
Created an attachment (id=18622)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18622&action=view)
testcase
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
2009-09-21 12:19 ` [Bug c++/41425] " Woebbeking at web dot de
@ 2009-09-21 12:21 ` Woebbeking at web dot de
2009-09-21 12:22 ` Woebbeking at web dot de
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From: Woebbeking at web dot de @ 2009-09-21 12:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from Woebbeking at web dot de 2009-09-21 12:21 -------
g++ case.cpp is sufficient to reproduce this.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
2009-09-21 12:19 ` [Bug c++/41425] " Woebbeking at web dot de
2009-09-21 12:21 ` Woebbeking at web dot de
@ 2009-09-21 12:22 ` Woebbeking at web dot de
2009-09-21 12:41 ` paolo dot carlini at oracle dot com
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From: Woebbeking at web dot de @ 2009-09-21 12:22 UTC (permalink / raw)
To: gcc-bugs
--
Woebbeking at web dot de changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |critical
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 12:22 ` Woebbeking at web dot de
@ 2009-09-21 12:41 ` paolo dot carlini at oracle dot com
2009-09-21 12:42 ` paolo dot carlini at oracle dot com
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From: paolo dot carlini at oracle dot com @ 2009-09-21 12:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from paolo dot carlini at oracle dot com 2009-09-21 12:41 -------
As far as I can see, you are triggering undefined behavior. Per 5.2.9/7: "A
value of integral or enumeration type can be explicitly converted to an
enumeration type. The value is unchanged if the original value is within the
range of the enumeration values (7.2). Otherwise, the resulting enumeration
value is unspecified."
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 12:41 ` paolo dot carlini at oracle dot com
@ 2009-09-21 12:42 ` paolo dot carlini at oracle dot com
2009-09-21 12:44 ` rguenth at gcc dot gnu dot org
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From: paolo dot carlini at oracle dot com @ 2009-09-21 12:42 UTC (permalink / raw)
To: gcc-bugs
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paolo dot carlini at oracle dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|critical |normal
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 12:42 ` paolo dot carlini at oracle dot com
@ 2009-09-21 12:44 ` rguenth at gcc dot gnu dot org
2009-09-21 12:54 ` Woebbeking at web dot de
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From: rguenth at gcc dot gnu dot org @ 2009-09-21 12:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rguenth at gcc dot gnu dot org 2009-09-21 12:44 -------
In C++ an enum type only has the minimum number of bits that is required to
store all its values, thus 1 in your case. So (foo)5 is a truncation.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |critical
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 12:44 ` rguenth at gcc dot gnu dot org
@ 2009-09-21 12:54 ` Woebbeking at web dot de
2009-09-21 13:08 ` rguenth at gcc dot gnu dot org
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From: Woebbeking at web dot de @ 2009-09-21 12:54 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from Woebbeking at web dot de 2009-09-21 12:53 -------
Paolo, but std::cout << static_cast<foo>(i); prints 5, so it's not the
conversion but the switch statement which is "broken".
Richard, if it's only truncation shouldn't case B be triggered?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 12:54 ` Woebbeking at web dot de
@ 2009-09-21 13:08 ` rguenth at gcc dot gnu dot org
2009-09-21 14:25 ` schwab at linux-m68k dot org
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From: rguenth at gcc dot gnu dot org @ 2009-09-21 13:08 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenth at gcc dot gnu dot org 2009-09-21 13:08 -------
Switch assembly is optimized if you handle all valid cases (which you do) into
if (i != 0)
case B
else
case A
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 13:08 ` rguenth at gcc dot gnu dot org
@ 2009-09-21 14:25 ` schwab at linux-m68k dot org
2009-09-21 14:46 ` paolo dot carlini at oracle dot com
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From: schwab at linux-m68k dot org @ 2009-09-21 14:25 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from schwab at linux-m68k dot org 2009-09-21 14:25 -------
(In reply to comment #3)
> As far as I can see, you are triggering undefined behavior.
There is a big difference between undefined and unspecified behaviour. With
unspecified behaviour the implementation must chose a consistent behaviour,
although it does not have to document which one it choses.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 14:25 ` schwab at linux-m68k dot org
@ 2009-09-21 14:46 ` paolo dot carlini at oracle dot com
2009-09-21 16:46 ` Woebbeking at web dot de
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From: paolo dot carlini at oracle dot com @ 2009-09-21 14:46 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from paolo dot carlini at oracle dot com 2009-09-21 14:45 -------
Agreed, unspecified, as the actual citation says.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 14:46 ` paolo dot carlini at oracle dot com
@ 2009-09-21 16:46 ` Woebbeking at web dot de
2009-09-22 11:43 ` rguenth at gcc dot gnu dot org
2010-05-04 4:48 ` jason at gcc dot gnu dot org
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From: Woebbeking at web dot de @ 2009-09-21 16:46 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from Woebbeking at web dot de 2009-09-21 16:46 -------
So it's ok to change the behavior in a minor release?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-21 16:46 ` Woebbeking at web dot de
@ 2009-09-22 11:43 ` rguenth at gcc dot gnu dot org
2010-05-04 4:48 ` jason at gcc dot gnu dot org
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From: rguenth at gcc dot gnu dot org @ 2009-09-22 11:43 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from rguenth at gcc dot gnu dot org 2009-09-22 11:43 -------
Yes, as part of a wrong-code fix.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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2009-09-21 12:17 [Bug c++/41425] New: switch with enums doesn't work Woebbeking at web dot de
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2009-09-22 11:43 ` rguenth at gcc dot gnu dot org
@ 2010-05-04 4:48 ` jason at gcc dot gnu dot org
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From: jason at gcc dot gnu dot org @ 2010-05-04 4:48 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from jason at gcc dot gnu dot org 2010-05-04 04:48 -------
In G++ 4.6 the confusing optimization will only be performed with
-fstrict-enums.
--
jason at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41425
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