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* [Bug c++/58894] New: C++11 lambda doesn't take const variable by reference
@ 2013-10-27 12:00 abyss.7 at gmail dot com
2013-10-27 13:08 ` [Bug c++/58894] " daniel.kruegler at googlemail dot com
2013-10-27 14:27 ` paolo.carlini at oracle dot com
0 siblings, 2 replies; 3+ messages in thread
From: abyss.7 at gmail dot com @ 2013-10-27 12:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58894
Bug ID: 58894
Summary: C++11 lambda doesn't take const variable by reference
Product: gcc
Version: 4.8.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: abyss.7 at gmail dot com
Trying to compile this code:
===
const int a = 1;
auto lambda = [&]() {
&a;
};
lambda();
===
g++ gives error: lvalue required as unary ‘&’ operand
>From gcc-bugs-return-432828-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sun Oct 27 12:17:34 2013
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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/58895] New: [SH] improve handling of signbit result
Date: Sun, 27 Oct 2013 12:17:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX895
Bug ID: 58895
Summary: [SH] improve handling of signbit result
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: olegendo at gcc dot gnu.org
Target: sh*-*-*
The handling of the result of the floating point signbit functions could be
improved in the following cases.
#include <cmath>
bool test0_OK (float x)
{
return !std::signbit (x);
}
-m4-single -m4 -O2:
flds fr4,fpul
sts fpul,r1
cmp/pz r1
rts
movt r0
----------------------
bool test1_NG (float x)
{
return std::signbit (x);
}
-m4-single -m4 -O2:
flds fr4,fpul
sts fpul,r1
cmp/pz r1
movt r0
rts
xor #1,r0
better:
flds fr4,fpul
sts fpul,r1
shll r1
rts
movt r1,r0
----------------------
void test2_OK (float x, int* y)
{
y[0] = !std::signbit (x);
}
-m4-single -m4 -O2:
flds fr4,fpul
sts fpul,r1
cmp/pz r1
movt r1
rts
mov.l r1,@r4
----------------------
void test3_NG (float x, int* y)
{
// c++11 std::signbit returns a bool
y[0] = std::signbit (x);
}
-m4-single -m4 -O2:
flds fr4,fpul
sts fpul,r1
cmp/pz r1
mov #-1,r1
negc r1,r1
rts
mov.l r1,@r4
better:
flds fr4,fpul
sts fpul,r2
shll r2
movt r1
rts
mov.l r1,@r4
----------------------
void test4_NG (float x, int* y)
{
// c99 signbit macro and corresponding built-in return
// zero or non-zero integer, i.e. MSB of x.
y[0] = __builtin_signbitf (x);
}
-m4-single -m4 -O2:
flds fr4,fpul
sts fpul,r2
mov.l .L7,r1
and r2,r1
rts
mov.l r1,@r4
.L8:
.align 2
.L7:
.long -2147483648
possible alternative without 32 bit constant.
smaller size, but probably slower.
flds fr4,fpul
sts fpul,r2
shll r2
movt r1
rotcr r1
rts
mov.l r1,@r4
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/58894] C++11 lambda doesn't take const variable by reference
2013-10-27 12:00 [Bug c++/58894] New: C++11 lambda doesn't take const variable by reference abyss.7 at gmail dot com
@ 2013-10-27 13:08 ` daniel.kruegler at googlemail dot com
2013-10-27 14:27 ` paolo.carlini at oracle dot com
1 sibling, 0 replies; 3+ messages in thread
From: daniel.kruegler at googlemail dot com @ 2013-10-27 13:08 UTC (permalink / raw)
To: gcc-bugs
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 3210 bytes --]
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58894
Daniel Krügler <daniel.kruegler at googlemail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |daniel.kruegler@googlemail.
| |com
--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
The code - as written - is invalid. Here is a valid form of this:
//-------------------------
int main() {
const int a = 1;
auto lambda = [&]() {
&a;
};
lambda();
}
//--------------------------
It still produces the mentioned diagnostics even in gcc 4.9.0 20131026
(experimental). It doesn't seem to be a regression, I can track it down back to
gcc 4.5.4
>From gcc-bugs-return-432832-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sun Oct 27 13:17:08 2013
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From: "jjcogliati-r1 at yahoo dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/53001] -Wfloat-conversion should be available to warn about floating point errors
Date: Sun, 27 Oct 2013 13:17:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idS001
--- Comment #27 from Joshua Cogliati <jjcogliati-r1 at yahoo dot com> ---
Created attachment 31097
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id1097&actioníit
Patch to add -Wfloat-conversion option against trunk with new testcase and
detailed warnings
This uses a detailed warnings in the testcase. I am not sure if this is a good
idea or not since it might get invalidated if the types change. It bootstraps
and the new testcase works on x86_64-unknown-linux-gnu
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/58894] C++11 lambda doesn't take const variable by reference
2013-10-27 12:00 [Bug c++/58894] New: C++11 lambda doesn't take const variable by reference abyss.7 at gmail dot com
2013-10-27 13:08 ` [Bug c++/58894] " daniel.kruegler at googlemail dot com
@ 2013-10-27 14:27 ` paolo.carlini at oracle dot com
1 sibling, 0 replies; 3+ messages in thread
From: paolo.carlini at oracle dot com @ 2013-10-27 14:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58894
Paolo Carlini <paolo.carlini at oracle dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-10-27
Blocks| |54367
Ever confirmed|0 |1
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-10-27 12:00 [Bug c++/58894] New: C++11 lambda doesn't take const variable by reference abyss.7 at gmail dot com
2013-10-27 13:08 ` [Bug c++/58894] " daniel.kruegler at googlemail dot com
2013-10-27 14:27 ` paolo.carlini at oracle dot com
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