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* [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation.
@ 2012-06-21 13:04 sbgccbug at yahoo dot co.uk
2012-06-21 13:35 ` [Bug c++/53745] " schwab@linux-m68k.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: sbgccbug at yahoo dot co.uk @ 2012-06-21 13:04 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Bug #: 53745
Summary: Bitshifted value (1 << 31) within enumerator class is
calculated incorrectly during compilation.
Classification: Unclassified
Product: gcc
Version: 4.6.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: sbgccbug@yahoo.co.uk
When compiling an 'enum class' (-std=c++0x) that uses bit-shifted values, the
result of "1 << 31" is calculated incorrectly, resulting in -0x80000000
(*negative* 2^31) rather than the correct result of 0x80000000:
// *** BEGIN EXAMPLE CODE (main.cpp) ***
enum class EnumTest : unsigned long int
{
A = 1 << 30,
B = 1 << 31
};
int main()
{
return 0;
}
// *** END EXAMPLE CODE ***
// *** BEGIN gcc-4.6.1 OUTPUT ***
main.cpp|4|error: enumerator value -0x00000000080000000 is too large for
underlying type ‘long unsigned int’|
// *** END gcc-4.6.1 OUTPUT ***
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation.
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
@ 2012-06-21 13:35 ` schwab@linux-m68k.org
2012-06-21 13:36 ` redi at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: schwab@linux-m68k.org @ 2012-06-21 13:35 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Andreas Schwab <schwab@linux-m68k.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #1 from Andreas Schwab <schwab@linux-m68k.org> 2012-06-21 13:35:26 UTC ---
1<<31 is an expression of type int, and overflows when int has 32 bits. This
is independent of the context of its use. You should write 1UL<<31 instead.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation.
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
2012-06-21 13:35 ` [Bug c++/53745] " schwab@linux-m68k.org
@ 2012-06-21 13:36 ` redi at gcc dot gnu.org
2012-06-21 17:52 ` [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer redi at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2012-06-21 13:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-21 13:36:24 UTC ---
The initializer must be converted constant expression of type unsigned long, so
by my reading it's ill-formed because (1<<31) has type int and is negative so
requires a narrowing conversion to unsigned long.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
2012-06-21 13:35 ` [Bug c++/53745] " schwab@linux-m68k.org
2012-06-21 13:36 ` redi at gcc dot gnu.org
@ 2012-06-21 17:52 ` redi at gcc dot gnu.org
2013-05-03 23:23 ` paolo.carlini at oracle dot com
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2012-06-21 17:52 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Last reconfirmed| |2012-06-21
Resolution|INVALID |
Summary|Bitshifted value (1 << 31) |[C++11] Poor diagnostic for
|within enumerator class is |ill-formed narrowing
|calculated incorrectly |conversion in enumerator
|during compilation. |initializer
Ever Confirmed|0 |1
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-21 17:51:43 UTC ---
Re-opening since the diagnostic could be better, the value is not "too large",
the problem is with the sign, not the magnitude.
enum E : unsigned long long { e = -1 };
e.cc:1:26: error: enumerator value -1 is too large for underlying type
'unsigned long long'
Clang gives a more accurate diagnostic, though not necessarily more helpful if
you don't know what a narrowing conversion is:
e.cc:1:25: error: enumerator value evaluates to -1, which cannot be narrowed to
type 'unsigned long long' [-Wc++11-narrowing]
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
` (2 preceding siblings ...)
2012-06-21 17:52 ` [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer redi at gcc dot gnu.org
@ 2013-05-03 23:23 ` paolo.carlini at oracle dot com
2013-05-04 13:09 ` paolo.carlini at oracle dot com
2013-05-05 0:29 ` paolo.carlini at oracle dot com
5 siblings, 0 replies; 7+ messages in thread
From: paolo.carlini at oracle dot com @ 2013-05-03 23:23 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Paolo Carlini <paolo.carlini at oracle dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vvnic.holas at gmail dot
| |com
--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-05-03 23:23:15 UTC ---
*** Bug 57164 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
` (3 preceding siblings ...)
2013-05-03 23:23 ` paolo.carlini at oracle dot com
@ 2013-05-04 13:09 ` paolo.carlini at oracle dot com
2013-05-05 0:29 ` paolo.carlini at oracle dot com
5 siblings, 0 replies; 7+ messages in thread
From: paolo.carlini at oracle dot com @ 2013-05-04 13:09 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Paolo Carlini <paolo.carlini at oracle dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |ASSIGNED
AssignedTo|unassigned at gcc dot |paolo.carlini at oracle dot
|gnu.org |com
--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-05-04 13:09:37 UTC ---
I'm going to propose changing the message to "... outside the range...",
similarly to ICC: it seems a good compromise, less misleading than the current
message, less technical than clang's.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer
2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
` (4 preceding siblings ...)
2013-05-04 13:09 ` paolo.carlini at oracle dot com
@ 2013-05-05 0:29 ` paolo.carlini at oracle dot com
5 siblings, 0 replies; 7+ messages in thread
From: paolo.carlini at oracle dot com @ 2013-05-05 0:29 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53745
Paolo Carlini <paolo.carlini at oracle dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
Target Milestone|--- |4.9.0
--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-05-05 00:29:13 UTC ---
Fixed for 4.9.0.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2013-05-05 0:29 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2012-06-21 13:04 [Bug c++/53745] New: Bitshifted value (1 << 31) within enumerator class is calculated incorrectly during compilation sbgccbug at yahoo dot co.uk
2012-06-21 13:35 ` [Bug c++/53745] " schwab@linux-m68k.org
2012-06-21 13:36 ` redi at gcc dot gnu.org
2012-06-21 17:52 ` [Bug c++/53745] [C++11] Poor diagnostic for ill-formed narrowing conversion in enumerator initializer redi at gcc dot gnu.org
2013-05-03 23:23 ` paolo.carlini at oracle dot com
2013-05-04 13:09 ` paolo.carlini at oracle dot com
2013-05-05 0:29 ` paolo.carlini at oracle dot com
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