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Date: Fri, 08 May 2015 23:17:42 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: He Kuang <hekuang@...wei.com>, a.p.zijlstra@...llo.nl,
acme@...nel.org, jolsa@...nel.org, mingo@...hat.com
CC: wangnan0@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] perf probe: Remove length limitation for showing
available variables
On 2015/05/08 21:23, He Kuang wrote:
> Use struct strbuf instead of bare char[] to remove the length limitation
> of variables in variable_list, so they will not disappear due to
> overlength, and make preparation for adding more description for
> variables.
Looks good to me, except one memory leak. please see below.
>
> Signed-off-by: He Kuang <hekuang@...wei.com>
> ---
> tools/perf/util/dwarf-aux.c | 50 +++++++++++++++++++-----------------------
> tools/perf/util/dwarf-aux.h | 4 ++--
> tools/perf/util/probe-finder.c | 16 ++++++++------
> 3 files changed, 33 insertions(+), 37 deletions(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index c34e024..75d264e 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -832,19 +832,17 @@ Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
> /**
> * die_get_typename - Get the name of given variable DIE
> * @vr_die: a variable DIE
> - * @buf: a buffer for result type name
> - * @len: a max-length of @buf
> + * @buf: a strbuf for result type name
> *
> - * Get the name of @vr_die and stores it to @buf. Return the actual length
> - * of type name if succeeded. Return -E2BIG if @len is not enough long, and
> - * Return -ENOENT if failed to find type name.
> + * Get the name of @vr_die and stores it to @buf. Return 0 if succeeded.
> + * and Return -ENOENT if failed to find type name.
> * Note that the result will stores typedef name if possible, and stores
> * "*(function_type)" if the type is a function pointer.
> */
> -int die_get_typename(Dwarf_Die *vr_die, char *buf, int len)
> +int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf)
> {
> Dwarf_Die type;
> - int tag, ret, ret2;
> + int tag, ret;
> const char *tmp = "";
>
> if (__die_get_real_type(vr_die, &type) == NULL)
> @@ -855,8 +853,8 @@ int die_get_typename(Dwarf_Die *vr_die, char *buf, int len)
> tmp = "*";
> else if (tag == DW_TAG_subroutine_type) {
> /* Function pointer */
> - ret = snprintf(buf, len, "(function_type)");
> - return (ret >= len) ? -E2BIG : ret;
> + strbuf_addf(buf, "(function_type)");
> + return 0;
> } else {
> if (!dwarf_diename(&type))
> return -ENOENT;
> @@ -867,39 +865,35 @@ int die_get_typename(Dwarf_Die *vr_die, char *buf, int len)
> else if (tag == DW_TAG_enumeration_type)
> tmp = "enum ";
> /* Write a base name */
> - ret = snprintf(buf, len, "%s%s", tmp, dwarf_diename(&type));
> - return (ret >= len) ? -E2BIG : ret;
> - }
> - ret = die_get_typename(&type, buf, len);
> - if (ret > 0) {
> - ret2 = snprintf(buf + ret, len - ret, "%s", tmp);
> - ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
> + strbuf_addf(buf, "%s%s", tmp, dwarf_diename(&type));
> + return 0;
> }
> + ret = die_get_typename(&type, buf);
> + if (ret == 0)
> + strbuf_addf(buf, "%s", tmp);
> +
> return ret;
> }
>
> /**
> * die_get_varname - Get the name and type of given variable DIE
> * @vr_die: a variable DIE
> - * @buf: a buffer for type and variable name
> - * @len: the max-length of @buf
> + * @buf: a strbuf for type and variable name
> *
> * Get the name and type of @vr_die and stores it in @buf as "type\tname".
> */
> -int die_get_varname(Dwarf_Die *vr_die, char *buf, int len)
> +int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf)
> {
> - int ret, ret2;
> + int ret;
>
> - ret = die_get_typename(vr_die, buf, len);
> + ret = die_get_typename(vr_die, buf);
> if (ret < 0) {
> pr_debug("Failed to get type, make it unknown.\n");
> - ret = snprintf(buf, len, "(unknown_type)");
> - }
> - if (ret > 0) {
> - ret2 = snprintf(buf + ret, len - ret, "\t%s",
> - dwarf_diename(vr_die));
> - ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
> + strbuf_addf(buf, "(unknown_type)");
> }
> - return ret;
> +
> + strbuf_addf(buf, "\t%s", dwarf_diename(vr_die));
> +
> + return 0;
> }
>
> diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> index af7dbcd..c0d6173 100644
> --- a/tools/perf/util/dwarf-aux.h
> +++ b/tools/perf/util/dwarf-aux.h
> @@ -114,8 +114,8 @@ extern Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
> Dwarf_Die *die_mem);
>
> /* Get the name of given variable DIE */
> -extern int die_get_typename(Dwarf_Die *vr_die, char *buf, int len);
> +extern int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf);
>
> /* Get the name and type of given variable DIE, stored as "type\tname" */
> -extern int die_get_varname(Dwarf_Die *vr_die, char *buf, int len);
> +extern int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf);
> #endif
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 63d3389..7b645ff40 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -1238,17 +1238,16 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
> return (ret < 0) ? ret : tf.ntevs;
> }
>
> -#define MAX_VAR_LEN 64
> -
> /* Collect available variables in this scope */
> static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
> {
> struct available_var_finder *af = data;
> struct variable_list *vl;
> - char buf[MAX_VAR_LEN];
> + struct strbuf buf;
> int tag, ret;
>
> vl = &af->vls[af->nvls - 1];
> + strbuf_init(&buf, 64);
>
> tag = dwarf_tag(die_mem);
> if (tag == DW_TAG_formal_parameter ||
> @@ -1257,10 +1256,13 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
> af->pf.fb_ops, &af->pf.sp_die,
> NULL);
> if (ret == 0) {
> - ret = die_get_varname(die_mem, buf, MAX_VAR_LEN);
> - pr_debug2("Add new var: %s\n", buf);
> - if (ret > 0)
> - strlist__add(vl->vars, buf);
> + ret = die_get_varname(die_mem, &buf);
> + pr_debug2("Add new var: %s\n", buf.buf);
> + if (ret == 0) {
> + strlist__add(vl->vars,
> + strbuf_detach(&buf, NULL));
> + }
> + strbuf_release(&buf);
It seems that this strbuf_release() should be called in any case,
since strbuf_init already allocated buffer.
> }
> }
so here is the good place to call, isn't it?
Thank you,
>
>
--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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