Bug #52165: Assertion failed: file .\dtoa.c, line 465

The failing assertion was written with the assumption that a NULL
string can never be passed to my_strtod(). However, an empty string
may be passed under some circumstances by passing str == NULL and
*end == NULL.

Fixed the assertion to take the above case into account.

mysql-test/r/func_misc.result

@@ -336,4 +336,13 @@ End of 5.0 tests
 select connection_id() > 0;
 connection_id() > 0
 1
+#
+# Bug #52165: Assertion failed: file .\dtoa.c, line 465
+# 
+CREATE TABLE t1 (a SET('a'), b INT);
+INSERT INTO t1 VALUES ('', 0);
+SELECT COALESCE(a) = COALESCE(b) FROM t1;
+COALESCE(a) = COALESCE(b)
+1
+DROP TABLE t1;
 End of tests

mysql-test/t/func_misc.test

@@ -467,4 +467,15 @@ select NAME_CONST('_id',1234) as id;
 
 select connection_id() > 0;
 
+--echo #
+--echo # Bug #52165: Assertion failed: file .\dtoa.c, line 465
+--echo # 
+
+CREATE TABLE t1 (a SET('a'), b INT);
+INSERT INTO t1 VALUES ('', 0);
+
+SELECT COALESCE(a) = COALESCE(b) FROM t1;
+
+DROP TABLE t1;
+
 --echo End of tests

strings/dtoa.c

@@ -462,7 +462,9 @@ double my_strtod(const char *str, char **end, int *error)
 {
   char buf[DTOA_BUFF_SIZE];
   double res;
-  DBUG_ASSERT(str != NULL && end != NULL && *end != NULL && error != NULL);
+  DBUG_ASSERT(end != NULL && ((str != NULL && *end != NULL) ||
+                              (str == NULL && *end == NULL))  &&
+              error != NULL);
 
   res= my_strtod_int(str, end, error, buf, sizeof(buf));
   return (*error == 0) ? res : (res < 0 ? -DBL_MAX : DBL_MAX);