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    SubjectRe: [PATCH 2/2] perf: use XSI-complaint version of strerror_r() instead of GNU-specific
    On Mon, Jul 23, 2012 at 02:00:33PM -0400, Ulrich Drepper wrote:
    > On Mon, Jul 23, 2012 at 11:00 AM, Kirill A. Shutemov
    > <kirill@shutemov.name> wrote:
    > > The right way to fix it is to switch to XSI-compliant version.
    >
    > And why exactly would this be "the right way"? Just fix the use of
    > strerror_r or use strerror_l.

    Okay. What about this:

    From 8b76ea28a09ebc72c7bdcc1d92e80a63a5cdaf1c Mon Sep 17 00:00:00 2001
    From: "Kirill A. Shutemov" <kirill@shutemov.name>
    Date: Mon, 23 Jul 2012 17:41:05 +0300
    Subject: [PATCH] perf: fix strerror_r() usage
    MIME-Version: 1.0
    Content-Type: text/plain; charset=UTF-8
    Content-Transfer-Encoding: 8bit

    Perf uses GNU-specific version of strerror_r(). The GNU-specific
    strerror_r() returns a pointer to a string containing the error message.
    This may be either a pointer to a string that the function stores in
    buf, or a pointer to some (immutable) static string (in which case buf
    is unused).

    In glibc-2.16 GNU version was marked with attribute warn_unused_result.
    It triggers few warnings in perf:

    util/target.c: In function ‘perf_target__strerror’:
    util/target.c:114:13: error: ignoring return value of ‘strerror_r’, declared with attribute warn_unused_result [-Werror=unused-result]
    ui/browsers/hists.c: In function ‘hist_browser__dump’:
    ui/browsers/hists.c:981:13: error: ignoring return value of ‘strerror_r’, declared with attribute warn_unused_result [-Werror=unused-result]

    They are bugs.

    Let's fix strerror_r() usage.

    Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
    ---
    tools/perf/ui/browsers/hists.c | 4 ++--
    tools/perf/util/target.c | 9 ++++++++-
    2 files changed, 10 insertions(+), 3 deletions(-)

    diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
    index 482f051..413bd62 100644
    --- a/tools/perf/ui/browsers/hists.c
    +++ b/tools/perf/ui/browsers/hists.c
    @@ -978,8 +978,8 @@ static int hist_browser__dump(struct hist_browser *browser)
    fp = fopen(filename, "w");
    if (fp == NULL) {
    char bf[64];
    - strerror_r(errno, bf, sizeof(bf));
    - ui_helpline__fpush("Couldn't write to %s: %s", filename, bf);
    + const char *err = strerror_r(errno, bf, sizeof(bf));
    + ui_helpline__fpush("Couldn't write to %s: %s", filename, err);
    return -1;
    }

    diff --git a/tools/perf/util/target.c b/tools/perf/util/target.c
    index 1064d5b..45ab408 100644
    --- a/tools/perf/util/target.c
    +++ b/tools/perf/util/target.c
    @@ -111,7 +111,14 @@ int perf_target__strerror(struct perf_target *target, int errnum,
    const char *msg;

    if (errnum >= 0) {
    - strerror_r(errnum, buf, buflen);
    + const char *err = strerror_r(errnum, buf, buflen);
    +
    + if (err != buf && buflen > 0) {
    + size_t len = strlen(err);
    + char *c = mempcpy(buf, err, min(buflen - 1, len));
    + *c = '\0';
    + }
    +
    return 0;
    }

    --
    Kirill A. Shutemov
    --
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