Re: [Qemu-devel] [PATCH 1/3] qemu-error: add {error, warn}_report_once_cond

[Markus Armbruster <armbru@redhat.com>]

Cornelia Huck <cohuck@redhat.com> writes:

> Add two functions to print an error/warning report once depending
> on a passed-in condition variable and flip it if printed. This is
> useful if you want to print a message not once-globally, but e.g.
> once-per-device.
>
> Inspired by warn_once() in hw/vfio/ccw.c.

This leaves the reader wondering why you don't replace that function.
You do, in PATCH 3.  I'd either announce that here, or squash the two
patches.

>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  include/qemu/error-report.h |  5 +++++
>  util/qemu-error.c           | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
>
> diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> index 72fab2b031..d2a6515e68 100644
> --- a/include/qemu/error-report.h
> +++ b/include/qemu/error-report.h
> @@ -44,6 +44,11 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  
> +void error_report_once_cond(bool *printed, const char *fmt, ...)
> +    GCC_FMT_ATTR(2, 3);
> +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> +    GCC_FMT_ATTR(2, 3);
> +
>  /*
>   * Similar to error_report(), except it prints the message just once.
>   * Return true when it prints, false otherwise.
> diff --git a/util/qemu-error.c b/util/qemu-error.c
> index a25d3b94c6..0894ab6995 100644
> --- a/util/qemu-error.c
> +++ b/util/qemu-error.c
> @@ -310,3 +310,47 @@ void info_report(const char *fmt, ...)
>      vreport(REPORT_TYPE_INFO, fmt, ap);
>      va_end(ap);
>  }
> +
> +/*
> + * If *printed is false, print an error message to current monitor if we
> + * have one, else to stderr, and flip *printed to true.
> + * If printed is NULL, do not print anything.

Any particular reason for supporting null @printed?

For what it's worth, warn_once() supports it, but its caller doesn't use
it.

> + * Format arguments like sprintf().  The resulting message should be
> + * a single phrase, with no newline or trailing punctuation.
> + * Prepend the current location and append a newline.
> + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> + */
> +void error_report_once_cond(bool *printed, const char *fmt, ...)
> +{
> +    va_list ap;
> +
> +    if (!printed || *printed) {
> +        return;
> +    }
> +    *printed = true;
> +    va_start(ap, fmt);
> +    vreport(REPORT_TYPE_ERROR, fmt, ap);
> +    va_end(ap);
> +}
> +
> +/*
> + * If *printed is false, print a warning message to current monitor if we
> + * have one, else to stderr, and flip *printed to true.
> + * If printed is NULL, do not print anything.
> + * Format arguments like sprintf().  The resulting message should be
> + * a single phrase, with no newline or trailing punctuation.
> + * Prepend the current location and append a newline.
> + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> + */
> +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> +{
> +    va_list ap;
> +
> +    if (!printed || *printed) {
> +        return;
> +    }
> +    *printed = true;
> +    va_start(ap, fmt);
> +    vreport(REPORT_TYPE_WARNING, fmt, ap);
> +    va_end(ap);
> +}