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SubjectRe: [RFC PATCH v4 05/29] bpf tools: Allow caller to set printing function
Hi Wang,

On Wed, May 27, 2015 at 05:19:40AM +0000, Wang Nan wrote:
> By libbpf_set_print(), users of libbpf are allowed to register he/she
> own debug, info and warning printing functions. Libbpf will use those
> functions to print messages. If not provided, default info and warning
> printing functions are fprintf(stderr, ...); defailt debug printing
> is NULL.
>
> This API is designed to be used by perf, enables it to register its own
> logging functions to make all logs uniform, instead of separated
> logging level control.
>
> Acked-by: Alexei Starovoitov <ast@plumgrid.com>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> ---
> tools/lib/bpf/libbpf.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 4 ++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index c08d6bc..49091c3 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -7,8 +7,51 @@
> */
>
> #include <stdlib.h>
> +#include <stdio.h>
> +#include <stdarg.h>
> +#include <string.h>
> #include <unistd.h>
> #include <asm/unistd.h>
> #include <linux/bpf.h>
>
> #include "libbpf.h"
> +
> +#define __printf(a, b) __attribute__((format(printf, a, b)))
> +
> +__printf(1, 2)
> +static int __base_pr(const char *format, ...)
> +{
> + va_list args;
> + int err;
> +
> + va_start(args, format);
> + err = vfprintf(stderr, format, args);
> + va_end(args);
> + return err;
> +}
> +
> +static __printf(1, 2) int (*__pr_warning)(const char *format, ...) =
> + __base_pr;
> +static __printf(1, 2) int (*__pr_info)(const char *format, ...) =
> + __base_pr;
> +static __printf(1, 2) int (*__pr_debug)(const char *format, ...) =
> + NULL;

What about using typedef for this.. like print_fn_t ?

Thanks,
Namhyung


> +
> +#define __pr(func, fmt, ...) \
> +do { \
> + if ((func)) \
> + (func)("libbpf: " fmt, ##__VA_ARGS__); \
> +} while(0)
> +
> +#define pr_warning(fmt, ...) __pr(__pr_warning, fmt, ##__VA_ARGS__)
> +#define pr_info(fmt, ...) __pr(__pr_info, fmt, ##__VA_ARGS__)
> +#define pr_debug(fmt, ...) __pr(__pr_debug, fmt, ##__VA_ARGS__)
> +
> +void libbpf_set_print(int (*warn)(const char *format, ...),
> + int (*info)(const char *format, ...),
> + int (*debug)(const char *format, ...))
> +{
> + __pr_warning = warn;
> + __pr_info = info;
> + __pr_debug = debug;
> +}
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index a6f46d9..430b122 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -8,4 +8,8 @@
> #ifndef __BPF_LIBBPF_H
> #define __BPF_LIBBPF_H
>
> +void libbpf_set_print(int (*warn)(const char *format, ...),
> + int (*info)(const char *format, ...),
> + int (*debug)(const char *format, ...));
> +
> #endif
> --
> 1.8.3.4
>


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