[libc] remove use after free in tests.

[michaelrj]

Summary

There were some tests added that attempted to access files after they
were closed to test errno behavior, this caused sanitizer issues. Those
portions of the tests have been disabled.

[sivachandra]

libc/test/src/stdio/fileop_test.cpp

128

Looks like these were added in https://reviews.llvm.org/D139576. If there are incorrect, they should be removed. If they are correct and the fix is expected to land separately, then please file a bug explaining the expected behavior in detail and add a TODO here which links to that bug.

libc/test/src/stdio/fileop_test.cpp

TEST(LlvmLibcFILETest, SimpleFileOperations) {
   ASSERT_EQ(__llvm_libc::fread(read_data, 1, sizeof(CONTENT) - 1, file),
             sizeof(CONTENT) - 1);
   read_data[sizeof(CONTENT) - 1] = '\0';
   ASSERT_STREQ(read_data, CONTENT);
   ASSERT_EQ(__llvm_libc::fclose(file), 0);
 
   // Check that the other functions correctly set errno.
 
-  errno = 0;
-  ASSERT_NE(__llvm_libc::fseek(file, 0, SEEK_SET), 0);
-  EXPECT_NE(errno, 0);
-
-  errno = 0;
-  ASSERT_NE(__llvm_libc::fclose(file), 0);
-  EXPECT_NE(errno, 0);
-
-  errno = 0;
-  ASSERT_EQ(__llvm_libc::fopen("INVALID FILE NAME", "r"),
-            static_cast<FILE *>(nullptr));
-  EXPECT_NE(errno, 0);
+  // errno = 0;
+  // ASSERT_NE(__llvm_libc::fseek(file, 0, SEEK_SET), 0);
+  // EXPECT_NE(errno, 0);
+
+  // errno = 0;
+  // ASSERT_NE(__llvm_libc::fclose(file), 0);
+  // EXPECT_NE(errno, 0);
+
+  // errno = 0;
+  // ASSERT_EQ(__llvm_libc::fopen("INVALID FILE NAME", "r"),
+  //           static_cast<FILE *>(nullptr));
+  // EXPECT_NE(errno, 0);
 }
 
 TEST(LlvmLibcFILETest, FFlush) {
   constexpr char FILENAME[] = "testdata/fflush.test";
   ::FILE *file = __llvm_libc::fopen(FILENAME, "w+");
   ASSERT_FALSE(file == nullptr);
   constexpr char CONTENT[] = "1234567890987654321";
   ASSERT_EQ(sizeof(CONTENT),

libc/test/src/stdio/ftell_test.cpp

void test_with_bufmode(int bufmode) {
     char data[READ_SIZE];
     // Reading a small amount will actually read out much more data and
     // buffer it. But, ftell should return the correct effective offset.
     ASSERT_EQ(READ_SIZE, __llvm_libc::fread(data, 1, READ_SIZE, file));
     ASSERT_EQ(size_t(__llvm_libc::ftell(file)), READ_SIZE);
 
     ASSERT_EQ(0, __llvm_libc::fclose(file));
 
-    errno = 0;
-    ASSERT_EQ(__llvm_libc::ftell(file), long(-1));
-    ASSERT_NE(errno, 0);
+    // errno = 0;
+    // ASSERT_EQ(__llvm_libc::ftell(file), long(-1));
+    // ASSERT_NE(errno, 0);
   }
 };
 
 TEST_F(LlvmLibcFTellTest, TellWithFBF) { test_with_bufmode(_IOFBF); }
 
 TEST_F(LlvmLibcFTellTest, TellWithNBF) { test_with_bufmode(_IONBF); }
 
 TEST_F(LlvmLibcFTellTest, TellWithLBF) { test_with_bufmode(_IOLBF); }