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

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Date:   Fri, 3 Nov 2017 21:26:32 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Joe Perches <joe@...ches.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org
Cc:     oss-drivers@...ronome.com, alexei.starovoitov@...il.com,
        daniel@...earbox.net
Subject: Re: [PATCH net-next 09/12] tools: bpftool: turn err() and info()
 macros into functions

2017-11-002 17:59 UTC-0700 ~ Joe Perches <joe@...ches.com>
> 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 ?

Hi Joe,
That's a good point. I wrote a patch to change that, Jakub posted it
some minutes ago. Thanks for your feedback!

Quentin