Re: [Qemu-devel] [PATCH v2 07/16] qapi: Drop support for escape sequences other than \\

[Eric Blake]

On 9/10/19 1:37 AM, Markus Armbruster wrote:
> Since the previous commit restricted strings to printable ASCII,
> \uXXXX's only use is obfuscation.  Drop it.
> 
> This leaves \\, \/, \', and \".  Since QAPI schema strings are all
> names, and names are restricted to ASCII letters, digits, hyphen, and
> underscore, none of them is useful.
> 
> The latter three have no test coverage.  Drop them.
> 
> Keep \\ to avoid (more) gratuitous incompatibility with JSON.

We have to parse it (to get a sane error message for someone writing
"a\b" and thinking they were getting a backspace), but we can still
reject "a\\b" as being a non-QAPI-name.  An alternative might be to
reject QAPI strings the moment \ is encountered (as the only possible
use is to introduce a character that is not valid as a name), to the
point that we could check for name validity at the time we parse strings
rather than later on.  Up to you.

> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---


> --- a/tests/qapi-schema/escape-outside-string.err
> +++ /dev/null
> @@ -1 +0,0 @@
> -tests/qapi-schema/escape-outside-string.json:3:27: Stray "\"

Do we still want to test that \ is an invalid character outside of
strings (whether or not \ is also made invalid inside strings)?

> +++ b/tests/qapi-schema/unknown-escape.json
> @@ -1,3 +1,3 @@
> -# we only recognize JSON escape sequences, plus our \' extension (no \x)
> +# we only recognize \\
>  # { 'command': 'foo', 'data': {} }
>  { 'command': 'foo', 'dat\x61':{} }
> 

At any rate, this change seems reasonable.

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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