bool

buf_page_is_checksum_valid_crc32(

        const byte*                     read_buf,

        ulint                           checksum_field1,

        ulint                           checksum_field2,

        bool                            use_legacy_big_endian)

{

        const uint32_t  crc32 = buf_calc_page_crc32(read_buf,

                                                    use_legacy_big_endian);

        if (checksum_field1 != checksum_field2) {

                goto invalid;

        }

        if (checksum_field1 == crc32) {

                return(true);

        } else {

                const uint32_t  crc32_legacy = buf_calc_page_crc32(read_buf, true);

                if (checksum_field1 == crc32_legacy) {

                        return(true);

                }

        }

It checks for both little endian and big endian variant of crc32 algorithm.

But in buf_page_is_corrupted():

                if (buf_page_is_checksum_valid_crc32(read_buf,

                        checksum_field1, checksum_field2, false)) {

                        return(false);

                }

                ...............

                .................

               /* We need to check whether the stored checksum matches legacy

                big endian checksum or Innodb checksum. We optimize the order

                based on earlier results. if earlier we have found pages

                matching legacy big endian checksum, we try to match it first.

                Otherwise we check innodb checksum first. */

                if (legacy_big_endian_checksum) {

                        if (buf_page_is_checksum_valid_crc32(read_buf,

                                checksum_field1, checksum_field2, true)) {

                                return(false);

                        }

                        legacy_checksum_checked = true;

                }

                ..............

                ..............

                /* If legacy checksum is not checked, do it now. */

                if (!legacy_checksum_checked && buf_page_is_checksum_valid_crc32(

                        read_buf, checksum_field1, checksum_field2, true)) {

                        legacy_big_endian_checksum = true;

                        return(false);

                }

                Above code can never be executed because these condition already checked as a part of

                buf_page_is_checksum_valid_crc32().

             /* We need to check whether the stored checksum matches legacy

                big endian checksum or Innodb checksum. We optimize the order

                based on earlier results. if earlier we have found pages

                matching legacy big endian checksum, we try to match it first.

                Otherwise we check innodb checksum first. */

                if (legacy_big_endian_checksum) {

                        const uint32_t calculated =

                                page_zip_calc_checksum(data, size, curr_algo, true);

                        if (stored == calculated) {

                                return(TRUE);

                        }

                        legacy_checksum_checked = true;

                }

            ............

            .............

                /* If legacy checksum is not checked, do it now. */

                if ((legacy_checksum_checked

                     && stored == calculated)) {

                        legacy_big_endian_checksum = true;

                        return(TRUE);

                }

            It is also kind of dead code because it should check if (!legacy_checksum_checked).

            may be merging error from mysql-5.7