[libvirt] [PATCH 1/3] docs: Teach apibuild to deal with (1U << 31) too

Peter Krempa pkrempa at redhat.com
Mon May 30 10:56:31 UTC 2016

On Mon, May 30, 2016 at 09:31:00 +0200, Michal Privoznik wrote:
> The apibuild script is a terrifying beast that parses some source
> files of ours and produces an XML representation of them. When it
> comes to parsing enums we have in some header files, it tries to
> be clever and detect a value that an enum member has (or if it is
> an alias for a different member). Whilst doing that it has to
> deal with values we give to the members in many formats. At some
> places we just pass the value in decimal:
> in other places, we use the aliasing:
> and in other places bitwise shifts are used:
>     VIR_CONNECT_GET_ALL_DOMAINS_STATS_ENFORCE_STATS = 1 << 31, /* enforce requested stats */
> The script tries to parse all of these resulting in the following
> tokens: "1", "VIR_CONNECT_LIST_DOMAINS_ACTIVE", "1<<31"; Then, the
> script tries to turn these into integers using python's eval()
> function. This function succeeds on the first and the last
> tokens. But, if we were to modify the last example so that it's
> of the following form:
>     VIR_CONNECT_GET_ALL_DOMAINS_STATS_ENFORCE_STATS = 1U << 31, /* enforce requested stats */
> the token representing enum's member value will then be "1U<<31".
> So our parsing is good. Unfortunately, python is not aware of the
> difference between signed and unsigned C types, therefore eval()
> fails over this token and the parser falls back thinking it's an
> alias to another enum member. Well it's not.
> The solution is to transform [0-9]U into [0-9] as for our
> purposes here it's the same thing.

I was worried that it might mangle aliases for other enums containing
numbers followed by a capital U but I didn't manage to break it.

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