netdev - Re: [PATCH net-next 09/12] tools: bpftool: turn err() and info() macros into functions

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Date:   Thu, 02 Nov 2017 17:59:05 -0700
From:   Joe Perches <joe@...ches.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org
Cc:     oss-drivers@...ronome.com, alexei.starovoitov@...il.com,
        daniel@...earbox.net, Quentin Monnet <quentin.monnet@...ronome.com>
Subject: Re: [PATCH net-next 09/12] tools: bpftool: turn err() and info()
 macros into functions

On Mon, 2017-10-23 at 09:24 -0700, Jakub Kicinski wrote:
> From: Quentin Monnet <quentin.monnet@...ronome.com>
> 
> Turn err() and info() macros into functions.
> 
> In order to avoid naming conflicts with variables in the code, rename
> them as p_err() and p_info() respectively.
> 
> The behavior of these functions is similar to the one of the macros for
> plain output. However, when JSON output is requested, these macros
> return a JSON-formatted "error" object instead of printing a message to
> stderr.
> 
> To handle error messages correctly with JSON, a modification was brought
> to their behavior nonetheless: the functions now append a end-of-line
> character at the end of the message. This way, we can remove end-of-line
> characters at the end of the argument strings, and not have them in the
> JSON output.
> 
> All error messages are formatted to hold in a single call to p_err(), in
> order to produce a single JSON field.

> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
> Acked-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
[]
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
[]
> @@ -97,4 +93,35 @@ int prog_parse_fd(int *argc, char ***argv);
>  void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes);
>  void print_hex_data_json(uint8_t *data, size_t len);
>  
> +static inline void p_err(const char *fmt, ...)
> +{
> +	va_list ap;
> +
> +	va_start(ap, fmt);
> +	if (json_output) {
> +		jsonw_start_object(json_wtr);
> +		jsonw_name(json_wtr, "error");
> +		jsonw_vprintf_enquote(json_wtr, fmt, ap);
> +		jsonw_end_object(json_wtr);
> +	} else {
> +		fprintf(stderr, "Error: ");
> +		vfprintf(stderr, fmt, ap);
> +		fprintf(stderr, "\n");
> +	}
> +	va_end(ap);
> +}

inline seems very wasteful.

Why not move p_err and p_info to common.c ?

> +
> +static inline void p_info(const char *fmt, ...)
> +{
> +	va_list ap;
> +
> +	if (json_output)
> +		return;
> +
> +	va_start(ap, fmt);
> +	vfprintf(stderr, fmt, ap);
> +	fprintf(stderr, "\n");
> +	va_end(ap);
> +}
>