On 09.04.25 12:25, Anshuman Khandual wrote:
On 4/9/25 15:51, David Hildenbrand wrote:
On 09.04.25 12:09, Anshuman Khandual wrote:
On 4/9/25 15:27, David Hildenbrand wrote:
On 09.04.25 11:50, Anshuman Khandual wrote:
Following build warning comes up for cow test as 'transferred' variable has not been initialized. Fix the warning via zero init for the variable.
CC cow cow.c: In function ‘do_test_vmsplice_in_parent’: cow.c:365:61: warning: ‘transferred’ may be used uninitialized [-Wmaybe-uninitialized] 365 | cur = read(fds[0], new + total, transferred - total); | ~~~~~~~~~~~~^~~~~~~ cow.c:296:29: note: ‘transferred’ was declared here 296 | ssize_t cur, total, transferred; | ^~~~~~~~~~~ CC compaction_test CC gup_longterm
Cc: Andrew Morton akpm@linux-foundation.org Cc: Shuah Khan shuah@kernel.org Cc: linux-mm@kvack.org Cc: linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual anshuman.khandual@arm.com
tools/testing/selftests/mm/cow.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c index f0cb14ea8608..b6cfe0a4b7df 100644 --- a/tools/testing/selftests/mm/cow.c +++ b/tools/testing/selftests/mm/cow.c @@ -293,7 +293,7 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size, .iov_base = mem, .iov_len = size, }; - ssize_t cur, total, transferred; + ssize_t cur, total, transferred = 0; struct comm_pipes comm_pipes; char *old, *new; int ret, fds[2];
if (before_fork) { transferred = vmsplice(fds[1], &iov, 1, 0); ...
if (!before_fork) { transferred = vmsplice(fds[1], &iov, 1, 0); ...
for (total = 0; total < transferred; total += cur) { ...
And I don't see any jump label that could jump to code that would ve using transferred.
What am I missing?
Probably because both those conditional statements are not mutually exclusive above with an if-else construct. Hence compiler flags it rather as a false positive ? Initializing with 0 just works around that false positive.
This is something the compiler should clearly be able to verify. before_fork is never changed in that function.
We should not work around wrong compilers.
Which compiler are you using such that you run into this issue?
gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
gcc (GCC) 14.2.1 20250110 (Red Hat 14.2.1-7)
Seems to be fine, just like all other compilers people used with this over the years.
Maybe something about that compiler is shaky that was fixed in the meantime?