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perf tools: use XSI-complaint version of strerror_r() instead of GNU-…

…specific

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>
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1 parent 4a841d6 commit 4cc49d4dc82a39a542a31c1f51ead08a46fd33f1 @kiryl kiryl committed with Arnaldo Carvalho de Melo Jul 23, 2012
Showing with 12 additions and 3 deletions.
  1. +2 −2 tools/perf/ui/browsers/hists.c
  2. +10 −1 tools/perf/util/target.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;
}
View
@@ -110,8 +110,17 @@ int perf_target__strerror(struct perf_target *target, int errnum,
int idx;
const char *msg;
+ BUG_ON(buflen > 0);
+
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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