[Spice-devel] [PATCH v2 05/13] Rephrase section about constants

[Frediano Ziglio]

> 
> From: Christophe de Dinechin <dinechin at redhat.com>
> 
> The indent of the rephrasing is that:
> 
> - If you have a single constant, use const, e.g. (visible in debugger)
>     const unsigned max_stuff = 42;
> 
> - If you have multiple constants, prefer enums over #define, as
>     already suggested later in the guide:
>     enum {
>        A = 0,
>        B = 42,
>        C = -1
>     }
> 

The const is a bit different from C and C++ and this results
in a bit of confusion. max_stuff above is a compile time
constant in C++, not in C while the enumeration is always
a compile time constant in both languages.
So the choice is not only syntax one.
I think that the "Alternatively, use global `const` variables."
is quite an ancient comment when spice-server was in C++
(much before I join and I think even older than the git repository!)
Unfortunately also C currently can't attach a type to the
enumeration values so if you want to define in C a constant
with a type usually you use a define like

#define MY_CONSTANT ((uint64_t)123)

You are right, this paragraph needs some care. Maybe the
style should be different for C and C++ and here we should
just use enum and #define while having a section for C++
telling about const ?

> Signed-off-by: Christophe de Dinechin <dinechin at redhat.com>
> ---
>  docs/spice_style.txt | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/spice_style.txt b/docs/spice_style.txt
> index 61cb0701..3e463d2f 100644
> --- a/docs/spice_style.txt
> +++ b/docs/spice_style.txt
> @@ -106,7 +106,9 @@ Using goto is allowed in C code for error handling. In
> any other case it will be
>  Defining Constant values
>  ------------------------
>  
> -Use defines for constant values for improving readability and ease of
> changes. Alternatively, use global `const` variables.
> +Use defines for constant values for improving readability and ease of
> changes.
> +Alternatively, use global `const` variables for individual values.
> +If multiple related constants are to be defined, consider the use of
> enumerations with initializers.
>  
>  Short functions
>  ---------------

Frediano