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* [Bug tree-optimization/53855] New: Emitting a warning for some dangling references.
@ 2012-07-04 16:36 ed at edrosten dot com
2012-07-04 18:18 ` [Bug middle-end/53855] Emitting a warning for use after clobber pinskia at gcc dot gnu.org
2012-07-05 8:40 ` rguenth at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: ed at edrosten dot com @ 2012-07-04 16:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53855
Bug #: 53855
Summary: Emitting a warning for some dangling references.
Classification: Unclassified
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: ed@edrosten.com
A dangling reference is created in the following code:
struct IntRef
{
IntRef(const int& v_)
:v(v_)
{
}
const int& v;
double get() const
{
return v;
}
};
struct BRef
{
BRef(const IntRef& v_)
:v(v_)
{
}
const IntRef& v;
double get() const
{
return v.get();
}
};
double test(const int& a)
{
const BRef c(a);
return c.get();
}
After the first stage of copy propagation, the representation of test is (from
test.cc.029t.copyprop1):
;; Function double test(const int&) (_Z4testRKi, funcdef_no=8, decl_uid=2230,
cgraph_uid=8)
double test(const int&) (const int & a)
{
const struct IntRef & c$v;
const struct IntRef & D.2286;
int D.2284;
const int & D.2283;
double D.2282;
const struct BRef c;
const struct IntRef D.2251;
<bb 2>:
D.2251.v = a_1(D);
D.2251 ={v} {CLOBBER};
D.2283_9 = D.2251.v;
D.2284_10 = *D.2283_9;
D.2282_11 = (double) D.2284_10;
return D.2282_11;
}
at which point is is quite obvious that D.2251 is used after it is CLOBBER'd.
Is it possible to add a feature to generate a warning in this case?
I'm using gcc version r189256 from SVN, but things are much the same in 4.7.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug middle-end/53855] Emitting a warning for use after clobber
2012-07-04 16:36 [Bug tree-optimization/53855] New: Emitting a warning for some dangling references ed at edrosten dot com
@ 2012-07-04 18:18 ` pinskia at gcc dot gnu.org
2012-07-05 8:40 ` rguenth at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2012-07-04 18:18 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53855
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
Component|tree-optimization |middle-end
Version|tree-ssa |4.7.0
Summary|Emitting a warning for some |Emitting a warning for use
|dangling references. |after clobber
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-07-04 18:18:19 UTC ---
Maybe the C++ front-end could warn about use of temp variables passed to
constructors.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug middle-end/53855] Emitting a warning for use after clobber
2012-07-04 16:36 [Bug tree-optimization/53855] New: Emitting a warning for some dangling references ed at edrosten dot com
2012-07-04 18:18 ` [Bug middle-end/53855] Emitting a warning for use after clobber pinskia at gcc dot gnu.org
@ 2012-07-05 8:40 ` rguenth at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-07-05 8:40 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53855
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2012-07-05
Ever Confirmed|0 |1
--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-05 08:40:06 UTC ---
Confirmed.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-07-04 16:36 [Bug tree-optimization/53855] New: Emitting a warning for some dangling references ed at edrosten dot com
2012-07-04 18:18 ` [Bug middle-end/53855] Emitting a warning for use after clobber pinskia at gcc dot gnu.org
2012-07-05 8:40 ` rguenth at gcc dot gnu.org
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