gcc4 warnings -Wuninitialized -Wfloat-equal and -Wconversion

[Thiago Macieira]

Em Quarta-feira 23 Setembro 2009, às 09:48:23, você escreveu:
> 2009/9/23 Thiago Macieira <thiago at kde.org>:
> > Em Terça-feira 22. Setembro 2009, às 22.18.08, Jaime Torres escreveu:
> >> using a struct like this:
> >>
> >> typedef enum {
> >>         LeftToRight,
> >>         RightToLeft
> >> } LayoutDirection_T;
> >>
> >> typedef struct
> >> {
> >>         LayoutDirection_T b:1;
> >> }
> >> LayoutDirection;
> >>
> >> test2.cpp compiles cleanly.
> >
> > How do you plan on placing a value inside that struct?
> >
> > Are you going to define a constructor, like this?
> >
> >    LayoutDirection(uint val) : b(val) {}
> >
> > Won't that generate the same warning?
> 
> Good point.
> Let's assume then that it is done right (do not use -Wconversion)
> until the compiler generates the good warnings for the bitfields. But
> I'll use it from time to time to reduce the warnings in non bitfields.

Don't apply this change anywhere in public API. It breaks compatibility.

Also note that two structs with one bit of each, side-by-side, do not occupy 
two bits in the same byte. In other words:

struct LayoutDirection
{ LayoutDirectionEnum b: 1; };
struct SomeOtherField
{ SomeOtherFieldEnum b: 1; };

struct Private1
{
    LayoutDirectionEnum layout :1;
    SomeOtherFieldEnum field : 1;
};
struct Private2
{
    LayoutDirection layout;
    SomeOtherField field;
};

sizeof(Private1) != sizeof(Private2)

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
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