Re: [Qemu-devel] [PATCH 5/5] qtest: Document calling conventions

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> We have two flavors of vararg usage in qtest; make it clear that
> qmp() has different semantics than hmp(), and let the compiler
> enforce that hmp() is used correctly. Since qmp() only accepts
> a subset of printf flags (namely, those that our JSON parser
> understands), I figured that it is probably not worth adding a
> format attribute to qmp() at this time.
>
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  tests/libqtest.h | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/tests/libqtest.h b/tests/libqtest.h
> index 38bc1e9..762ed13 100644
> --- a/tests/libqtest.h
> +++ b/tests/libqtest.h
> @@ -50,7 +50,8 @@ void qtest_quit(QTestState *s);
>  /**
>   * qtest_qmp_discard_response:
>   * @s: #QTestState instance to operate on.
> - * @fmt...: QMP message to send to qemu
> + * @fmt...: QMP message to send to qemu; only recognizes formats
> + * understood by json-lexer.c
>   *
>   * Sends a QMP message to QEMU and consumes the response.
>   */

These formats are chosen so that gcc can help us check them.  Please add
GCC_FMT_ATTR().  Precedence: qobject_from_jsonf().

Where are the "formats understood by json-lexer.c" documented?

More of the same below.

> @@ -59,7 +60,8 @@ void qtest_qmp_discard_response(QTestState *s, const char *fmt, ...);
>  /**
>   * qtest_qmp:
>   * @s: #QTestState instance to operate on.
> - * @fmt...: QMP message to send to qemu
> + * @fmt...: QMP message to send to qemu; only recognizes formats
> + * understood by json-lexer.c
>   *
>   * Sends a QMP message to QEMU and returns the response.
>   */
> @@ -134,14 +136,14 @@ QDict *qtest_qmp_eventwait_ref(QTestState *s, const char *event);
>  /**
>   * qtest_hmp:
>   * @s: #QTestState instance to operate on.
> - * @fmt...: HMP command to send to QEMU
> + * @fmt...: HMP command to send to QEMU, passed through sprintf()

Not actually through sprintf(), but I get what you mean.  I like to
document such things as "Format arguments like vsprintf()."

>   *
>   * Send HMP command to QEMU via QMP's human-monitor-command.
>   * QMP events are discarded.
>   *
>   * Returns: the command's output.  The caller should g_free() it.
>   */
> -char *qtest_hmp(QTestState *s, const char *fmt, ...);
> +char *qtest_hmp(QTestState *s, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
>
>  /**
>   * qtest_hmpv:
> @@ -535,7 +537,8 @@ static inline void qtest_end(void)
>
>  /**
>   * qmp:
> - * @fmt...: QMP message to send to qemu
> + * @fmt...: QMP message to send to qemu; only recognizes formats
> + * understood by json-lexer.c
>   *
>   * Sends a QMP message to QEMU and returns the response.
>   */
> @@ -543,7 +546,8 @@ QDict *qmp(const char *fmt, ...);
>
>  /**
>   * qmp_async:
> - * @fmt...: QMP message to send to qemu
> + * @fmt...: QMP message to send to qemu; only recognizes formats
> + * understood by json-lexer.c
>   *
>   * Sends a QMP message to QEMU and leaves the response in the stream.
>   */
> @@ -551,7 +555,8 @@ void qmp_async(const char *fmt, ...);
>
>  /**
>   * qmp_discard_response:
> - * @fmt...: QMP message to send to qemu
> + * @fmt...: QMP message to send to qemu; only recognizes formats
> + * understood by json-lexer.c
>   *
>   * Sends a QMP message to QEMU and consumes the response.
>   */
> @@ -592,13 +597,13 @@ static inline QDict *qmp_eventwait_ref(const char *event)
>
>  /**
>   * hmp:
> - * @fmt...: HMP command to send to QEMU
> + * @fmt...: HMP command to send to QEMU, passed through printf()

Here, you claim printf().  Typo?

>   *
>   * Send HMP command to QEMU via QMP's human-monitor-command.
>   *
>   * Returns: the command's output.  The caller should g_free() it.
>   */
> -char *hmp(const char *fmt, ...);
> +char *hmp(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>
>  /**
>   * get_irq: