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    SubjectRe: [PATCH 15/19] perf tools: use XSI-complaint version of strerror_r() instead of GNU-specific
    Date
    On Wed, 25 Jul 2012 14:41:30 -0300, Arnaldo Carvalho de Melo wrote:
    > From: Kirill A. Shutemov <kirill@shutemov.name>
    >
    > 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>
    > Acked-by: Ulrich Drepper <drepper@gmail.com>
    > Cc: Ingo Molnar <mingo@kernel.org>
    > Cc: Paul Mackerras <paulus@samba.org>
    > Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > Cc: Ulrich Drepper <drepper@gmail.com>
    > Link: http://lkml.kernel.org/r/20120723210654.GA25248@shutemov.name
    > [ committer note: s/assert/BUG_ON/g ]
    > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    > ---
    > tools/perf/ui/browsers/hists.c | 4 ++--
    > tools/perf/util/target.c | 11 ++++++++++-
    > 2 files changed, 12 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..3f59c49 100644
    > --- a/tools/perf/util/target.c
    > +++ b/tools/perf/util/target.c
    > @@ -110,8 +110,17 @@ int perf_target__strerror(struct perf_target *target, int errnum,
    > int idx;
    > const char *msg;
    >
    > + BUG_ON(buflen > 0);
    > +

    No! It should be

    BUG_ON(buflen == 0);

    Thanks,
    Namhyung


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