mysqldump restores a negative zero as a positive zero

Hello and thank you for MariaDB,

While importing a database using mysqldump, I noticed table checksums were not the same, a diff on the mysqldump showed that negative zero values in a double field were represented as -0 in the mysqldump which was being imported as positive zero when the mysqldump was run using the mysql client.

If I add the following to mysql-test/t/mysqldump_restore.test , notice to obtain a negative zero I enclose it in quotes:

--echo #

--echo # Negative zero

--echo #

CREATE TABLE t1 (a double);

INSERT INTO t1 VALUES ('-0');

--exec $MYSQL_DUMP --compact test t1 > $mysqldumpfile

let $table_name = test.t1;

--source include/mysqldump.inc

and then run:

./mysql-test-run mysqldump_restore

...

# Recreate table from mysqldump output

# Compare original and recreated tables

# Recreated table: test.t1

# Original table: test.t1_orig

include/diff_tables.inc [test.t1, test.t1_orig]

--- mysql-test/var/mysqld.1/data//diff_table--test-t1   2015-10-09 07:51:27.890186982 -0400

+++ mysql-test/var/mysqld.1/data//diff_table--test-t1_orig      2015-10-09 07:51:27.918591757 -0400

@@ -1 +1 @@

-0

+-0

I suspect in the case of the data being worked on that the negative zero was written as a string in error, and had it been numeric then it would have been stored as positive zero and we would have not seen a difference between the original and restored data.

I am not sure if test_if_special_chars in client/mysqldump.c could return 1 if passed "-0", or if INSERT -0 should be expected to store a negative zero.

Thank you.