-Wunused-but-set-variable building perf

[nickdesaulniers]

$ make LLVM=1 -C tools/perf
...
event-parse.c:112:13: warning: variable 'x' set but not used [-Wunused-but-set-variable]
        static int x;
                   ^
...
tests/mmap-basic.c:117:8: error: variable 'foo' set but not used [-Werror,-Wunused-but-set-variable]
                        int foo = syscalls[i]();
                            ^
...
tests/perf-record.c:68:16: error: variable 'errs' set but not used [-Werror,-Wunused-but-set-variable]
        int err = -1, errs = 0, i, wakeups = 0;
                      ^
...
util/parse-events-bison.c:1401:9: error: variable 'parse_events_nerrs' set but not used [-Werror,-Wunused-but-set-variable]
    int yynerrs = 0;
        ^

[nathanchance]

These are exposed by llvm/llvm-project@2af845a; GCC has -Wunused-but-set-variable as well but it does not warn for the increment/decrement operations.

For what it's worth, the perf build is broken for me on Arch Linux for other reasons (newer Perl it seems).

[dileks]

Link: https://lore.kernel.org/r/20220607000851.39798-1-irogers@google.com

Pending Git pull request:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=perf-tools-fixes-for-v5.19-2022-06-19

[dileks]

Patch perf unwind: Fix uninitialized variable in Linus Git.

[1] https://git.kernel.org/linus/1d98cdf7fa2bc6e8063c0a692a1c091d8ebe3a75

[nathanchance]

I think that change is for a different issue?

[nickdesaulniers]

diff --git a/tools/perf/tests/mmap-basic.c b/tools/perf/tests/mmap-basic.c
index 30bbe144648a..cac1e5ab9b0e 100644
--- a/tools/perf/tests/mmap-basic.c
+++ b/tools/perf/tests/mmap-basic.c
@@ -113,10 +113,8 @@ static int test__basic_mmap(struct test_suite *test __maybe_unused, int subtest
        }
 
        for (i = 0; i < nsyscalls; ++i)
-               for (j = 0; j < expected_nr_events[i]; ++j) {
-                       int foo = syscalls[i]();
-                       ++foo;
-               }
+               for (j = 0; j < expected_nr_events[i]; ++j)
+                       syscalls[i]();
 
        md = &evlist->mmap[0];
        if (perf_mmap__read_init(&md->core) < 0)
diff --git a/tools/perf/tests/perf-record.c b/tools/perf/tests/perf-record.c
index 6a001fcfed68..d9165236e473 100644
--- a/tools/perf/tests/perf-record.c
+++ b/tools/perf/tests/perf-record.c
@@ -332,7 +332,7 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 out:
        if (err == -EACCES)
                return TEST_SKIP;
-       if (err < 0)
+       if (err < 0 || errs)
                return TEST_FAIL;
        return TEST_OK;
 }

Let me see if I can figure out the right way to fix the rest.

[nickdesaulniers]

https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=tmp.perf/urgent&id=25c5e67cdf744cbb93fd06647611d3036218debe
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=tmp.perf/urgent&id=689a91c65a129136cb6d9314a395c0f70a79584e
Look related, but not closing out until verified.