[PATCH bpf-next] selftests/bpf: fix GCC11 compiler warnings in -O2 mode

[PATCH bpf-next] selftests/bpf: fix GCC11 compiler warnings in -O2 mode

[Andrii Nakryiko]

When compiling selftests in -O2 mode with GCC1, we get three new
compilations warnings about potentially uninitialized variables.

Compiler is wrong 2 out of 3 times, but this patch makes GCC11 happy
anyways, as it doesn't cost us anything and makes optimized selftests
build less annoying.

The amazing one is tc_redirect case of token that is malloc()'ed before
ASSERT_OK_PTR() check is done on it. Seems like GCC pessimistically
assumes that libbpf_get_error() will dereference the contents of the
pointer (no it won't), so the only way I found to shut GCC up was to do
zero-initializaing calloc(). This one was new to me.

For linfo case, GCC didn't realize that linfo_size will be initialized
by the function that is returning linfo_size as out parameter.

core_reloc.c case was a real bug, we can goto cleanup before initializing
obj. But we don't need to do any clean up, so just continue iteration
intstead.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/testing/selftests/bpf/prog_tests/btf.c         | 2 +-
 tools/testing/selftests/bpf/prog_tests/core_reloc.c  | 2 +-
 tools/testing/selftests/bpf/prog_tests/tc_redirect.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index 8b652f5ce423..ec823561b912 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -6556,7 +6556,7 @@ static int test_get_linfo(const struct prog_info_raw_test *test,
 static void do_test_info_raw(unsigned int test_num)
 {
 	const struct prog_info_raw_test *test = &info_raw_tests[test_num - 1];
-	unsigned int raw_btf_size, linfo_str_off, linfo_size;
+	unsigned int raw_btf_size, linfo_str_off, linfo_size = 0;
 	int btf_fd = -1, prog_fd = -1, err = 0;
 	void *raw_btf, *patched_linfo = NULL;
 	const char *ret_next_str;
diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index b8bdd1c3efca..68e4c8dafa00 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -872,7 +872,7 @@ void test_core_reloc(void)
 		if (test_case->btf_src_file) {
 			err = access(test_case->btf_src_file, R_OK);
 			if (!ASSERT_OK(err, "btf_src_file"))
-				goto cleanup;
+				continue;
 		}
 
 		open_opts.btf_custom_path = test_case->btf_src_file;
diff --git a/tools/testing/selftests/bpf/prog_tests/tc_redirect.c b/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
index c2426df58e17..647b0a833628 100644
--- a/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
+++ b/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
@@ -140,7 +140,7 @@ static struct nstoken *open_netns(const char *name)
 	int err;
 	struct nstoken *token;
 
-	token = malloc(sizeof(struct nstoken));
+	token = calloc(1, sizeof(struct nstoken));
 	if (!ASSERT_OK_PTR(token, "malloc token"))
 		return NULL;
 
-- 
2.30.2

Re: [PATCH bpf-next] selftests/bpf: fix GCC11 compiler warnings in -O2 mode

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Fri, 11 Feb 2022 11:09:27 -0800 you wrote:
> When compiling selftests in -O2 mode with GCC1, we get three new
> compilations warnings about potentially uninitialized variables.
> 
> Compiler is wrong 2 out of 3 times, but this patch makes GCC11 happy
> anyways, as it doesn't cost us anything and makes optimized selftests
> build less annoying.
> 
> [...]

Here is the summary with links:
  - [bpf-next] selftests/bpf: fix GCC11 compiler warnings in -O2 mode
    https://git.kernel.org/bpf/bpf-next/c/d3b0b80064e0

You are awesome, thank you!
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