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[122.26.212.247]) by smtp.googlemail.com with ESMTPSA id d9443c01a7336-2a2f3d4cbdasm438563655ad.65.2026.01.04.18.36.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 Jan 2026 18:36:57 -0800 (PST) From: Daniel Palmer To: w@1wt.eu, linux@weissschuh.net Cc: david.laight.linux@gmail.com, linux-kernel@vger.kernel.org, Daniel Palmer Subject: [PATCH v2 3/3] tools/nolibc: Add a simple test for writing to a FILE and reading it back Date: Mon, 5 Jan 2026 11:36:29 +0900 Message-ID: <20260105023629.1502801-4-daniel@thingy.jp> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260105023629.1502801-1-daniel@thingy.jp> References: <20260105023629.1502801-1-daniel@thingy.jp> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a test that exercises create->write->seek->read to check that using the stream functions (fwrite() etc) is not totally broken. The only edge cases this is testing for are: - Reading the file after writing but without rewinding reads nothing. - Trying to read more items than the file contains returns the count of fully read items. Signed-off-by: Daniel Palmer --- tools/testing/selftests/nolibc/nolibc-test.c | 53 ++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/s= elftests/nolibc/nolibc-test.c index 3c5a226dad3a..6d99698005c4 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -877,6 +877,58 @@ int test_file_stream(void) return 0; } =20 +int test_file_stream_wsr(void) +{ + const char dataout[] =3D "foo"; + const size_t datasz =3D sizeof(dataout); + char datain[datasz]; + int fd, r; + FILE *f; + + fd =3D open("/tmp", O_TMPFILE | O_RDWR, 0644); + if (fd =3D=3D -1) + return -1; + + f =3D fdopen(fd, "w+"); + if (!f) + return -1; + + errno =3D 0; + r =3D fwrite(dataout, 1, datasz, f); + if (r !=3D datasz) + return -1; + + /* Attempt to read from the file without rewinding, + * we should read 0 items. + */ + r =3D fread(datain, 1, datasz, f); + if (r) + return -1; + + /* Rewind the file to the start */ + r =3D fseek(f, 0, SEEK_SET); + if (r) + return -1; + + /* Attempt to read back more than was written to + * make sure we handle short reads properly. + * fread() should return the number of complete items. + */ + r =3D fread(datain, 1, datasz + 1, f); + if (r !=3D datasz) + return -1; + + /* Data we read should match the data we just wrote */ + if (memcmp(datain, dataout, datasz) !=3D 0) + return -1; + + r =3D fclose(f); + if (r) + return -1; + + return 0; +} + enum fork_type { FORK_STANDARD, FORK_VFORK, @@ -1351,6 +1403,7 @@ int run_syscall(int min, int max) CASE_TEST(fchdir_stdin); EXPECT_SYSER(1, fchdir(STDIN_FILENO), -1, = ENOTDIR); break; CASE_TEST(fchdir_badfd); EXPECT_SYSER(1, fchdir(-1), -1, EBADF); br= eak; CASE_TEST(file_stream); EXPECT_SYSZR(1, test_file_stream()); break; + CASE_TEST(file_stream_wsr); EXPECT_SYSZR(1, test_file_stream_wsr()); b= reak; CASE_TEST(fork); EXPECT_SYSZR(1, test_fork(FORK_STANDARD));= break; CASE_TEST(getdents64_root); EXPECT_SYSNE(1, test_getdents64("/"), -1);= break; CASE_TEST(getdents64_null); EXPECT_SYSER(1, test_getdents64("/dev/null= "), -1, ENOTDIR); break; --=20 2.51.0