Re: [Boost-users] [weak_ptr] thread safe?

From: Michael Fawcett (michael.fawcett_at_[hidden])
Date: 2006-04-19 13:09:20

On 4/19/06, John Wilkinson <jwilkinson_at_[hidden]> wrote:
> There is a pragma in VC6 that will activate or deactivate optimization.
> It can be used to wrap optimization-sensitive blocks of code.  I do not
> remember what it is, though, and I do not have VC6 handy.  I have used
> it, and it did alleviate an optimization-related bug.

>From the MSDN:

#pragma optimize( "[optimization-list]", {on | off} )

Specifies optimizations to be performed on a function-by-function
basis. The optimize pragma must appear outside a function and takes
effect at the first function defined after the pragma is seen. The on
and off arguments turn options specified in the optimization-list on
or off.

The optimization-list can be zero or more of the parameters shown in
the following table.
Parameters of the optimize Pragma
Parameter(s)Type of optimization
a          Assume no aliasing.
g          Enable global optimizations.
p          Improve floating-point consistency.
s or t    Specify short or fast sequences of machine code.
w         Assume that aliasing can occur across function calls
(achieves the same effect as /Ow).
y          Generate frame pointers on the program stack.

These are the same letters used with the /O compiler options. For example:

#pragma optimize( "atp", on )
Using the optimize pragma with the empty string ("") is a special form
of the directive:
When you use the off parameter, it turns the optimizations, listed in
the table above, off.
When you use the on parameter, it resets the optimizations to those
that you specified with the /O compiler option.

#pragma optimize( "", off )
.
.
.
#pragma optimize( "", on )

HTH,

Michael Fawcett