[Spice-devel] [PATCH spice-common 1/2] quic: constantify some variable

[Frediano Ziglio]

> 
> Hi
> 
> ----- Original Message -----
> > > 
> > > ----- Original Message -----
> > > > Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> > > > ---
> > > >  common/quic.c | 6 +++---
> > > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/common/quic.c b/common/quic.c
> > > > index 5b00d65..59565ae 100644
> > > > --- a/common/quic.c
> > > > +++ b/common/quic.c
> > > > @@ -173,13 +173,13 @@ struct Encoder {
> > > >  };
> > > >  
> > > >  /* target wait mask index */
> > > > -static int wmimax = DEFwmimax;
> > > > +static const int wmimax = DEFwmimax;
> > > >  
> > > >  /* number of symbols to encode before increasing wait mask index */
> > > > -static int wminext = DEFwminext;
> > > > +static const int wminext = DEFwminext;
> > > >  
> > > >  /* model evolution mode */
> > > > -static int evol = DEFevol;
> > > > +static const int evol = DEFevol;
> > > >  
> > > >  /* bppmask[i] contains i ones as lsb-s */
> > > >  static const unsigned long int bppmask[33] = {
> > > 
> > > 
> > > Ah right, you fixed it here. I wonder if we should stick to a upper case
> > > convention for const global values. And I wonder if it shouldn't be a
> > > #define instead.
> > > 
> > 
> > Usually for compatibility I use defines but I don't think is
> > a big problem for the compilers we use. A static const should be
> > a compile time constant (OT: a non static one is not so in C
> > but so in C++).
> > 
> 
> I am not thinking about compile-time optimization, but rather making clear
> that the value can't be tweaked (even with a debugger) by using upper-case
> macro convention.
> > Frediano
> > 
> 

A compile time constant and a define requires the same kind of tweaks
from a debugger prospective. The only difference from a debugger is
that with the define macro you don't see the mnemonic.
As a developer if I read "static const" I assume is a constant
(I don't really understand your confusion here). And on the usage
occurrences (like "switch (evol)") the compiler won't allow me to change
the constant. I think this code was written that way to allow to change
(maybe even at runtime) these variable so it made sense.

Frediano