linux-kernel - [PATCH v6.19-rc1 1/1] libperf: Use 'extern' in LIBPERF

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Message-ID: <aTGyxZizJtieaT1S@x1>
Date: Thu, 4 Dec 2025 13:11:49 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: [PATCH v6.19-rc1 1/1] libperf: Use 'extern' in LIBPERF_API
 visibility macro

Use 'extern' on LIBPERF_API to address this issue that started appearing
with gcc 15, first seen in ubuntu 25.10:

  evlist.c: In function 'perf_evlist__purge':
  evlist.c:202:17: error: implicit declaration of function 'perf_evsel__delete'; did you mean 'perf_evsel__exit'? [-Wimplicit-function-declaration]
    202 |                 perf_evsel__delete(pos);
        |                 ^~~~~~~~~~~~~~~~~~
        |                 perf_evsel__exit
  evlist.c:202:17: error: nested extern declaration of 'perf_evsel__delete' [-Werror=nested-externs]
  evlist.c: In function 'perf_evlist__open':
  evlist.c:261:23: error: implicit declaration of function 'perf_evsel__open'; did you mean 'perf_evsel__exit'? [-Wimplicit-function-declaration]
    261 |                 err = perf_evsel__open(evsel, evsel->cpus, evsel->threads);
        |                       ^~~~~~~~~~~~~~~~
        |                       perf_evsel__exit
  evlist.c:261:23: error: nested extern declaration of 'perf_evsel__open' [-Werror=nested-externs]

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Ian Rogers <irogers@...gle.com>
Cc: James Clark <james.clark@...aro.org>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
[ v1 used -std=gnu17 to workaround this kinda like libbpf, use extern as suggested by Namhyung ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/lib/perf/include/perf/core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/perf/include/perf/core.h b/tools/lib/perf/include/perf/core.h
index a3f6d68edad76240..06cc132d88cf3436 100644
--- a/tools/lib/perf/include/perf/core.h
+++ b/tools/lib/perf/include/perf/core.h
@@ -5,7 +5,7 @@
 #include <stdarg.h>
 
 #ifndef LIBPERF_API
-#define LIBPERF_API __attribute__((visibility("default")))
+#define LIBPERF_API extern __attribute__((visibility("default")))
 #endif
 
 enum libperf_print_level {
-- 
2.52.0