From 36ab257491c3021680c4d845c4690e3e294c2436 Mon Sep 17 00:00:00 2001
From: Tor Didriksen <tor.didriksen@oracle.com>
Date: Wed, 17 Nov 2010 16:39:35 +0100
Subject: [PATCH] Bug #58137 char(0) column cause: my_gcvt: Assertion `width >
 0 && to != ((void *)0)' failed

mysql-test/r/func_math.result:
  Add test for Bug #58137
mysql-test/t/func_math.test:
  Add test for Bug #58137
sql/field.cc:
  Skip calling my_gcvt() if we are trying to insert a double into a char(0) column.
---
 mysql-test/r/func_math.result | 9 +++++++++
 mysql-test/t/func_math.test   | 8 ++++++++
 sql/field.cc                  | 9 ++++++---
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/mysql-test/r/func_math.result b/mysql-test/r/func_math.result
index bfb3af0afff..835715ac51e 100644
--- a/mysql-test/r/func_math.result
+++ b/mysql-test/r/func_math.result
@@ -607,3 +607,12 @@ SELECT floor(log10(format(concat_ws(5445796E25, 5306463, 30837), -358821)))
 as foo;
 foo
 2
+#
+# Bug #58137 char(0) column cause:
+#            my_gcvt: Assertion `width > 0 && to != ((void *)0)' failed
+#
+CREATE TABLE t1(a char(0));
+INSERT INTO t1 (SELECT -pi());
+Warnings:
+Warning	1265	Data truncated for column 'a' at row 1
+DROP TABLE t1;
diff --git a/mysql-test/t/func_math.test b/mysql-test/t/func_math.test
index efdf7201a40..5d5dea74e28 100644
--- a/mysql-test/t/func_math.test
+++ b/mysql-test/t/func_math.test
@@ -464,3 +464,11 @@ SELECT -9223372036854775808 MOD -1;
 --echo #
 SELECT floor(log10(format(concat_ws(5445796E25, 5306463, 30837), -358821)))
 as foo;
+
+--echo #
+--echo # Bug #58137 char(0) column cause:
+--echo #            my_gcvt: Assertion `width > 0 && to != ((void *)0)' failed
+--echo #
+CREATE TABLE t1(a char(0));
+INSERT INTO t1 (SELECT -pi());
+DROP TABLE t1;
diff --git a/sql/field.cc b/sql/field.cc
index a9b5fedda2d..e5cae9ea8e3 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -6327,10 +6327,13 @@ int Field_str::store(double nr)
   ASSERT_COLUMN_MARKED_FOR_WRITE;
   char buff[DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE];
   uint local_char_length= field_length / charset()->mbmaxlen;
-  size_t length;
-  my_bool error;
+  size_t length= 0;
+  my_bool error= (local_char_length == 0);
+
+  // my_gcvt() requires width > 0, and we may have a CHAR(0) column.
+  if (!error)
+    length= my_gcvt(nr, MY_GCVT_ARG_DOUBLE, local_char_length, buff, &error);
 
-  length= my_gcvt(nr, MY_GCVT_ARG_DOUBLE, local_char_length, buff, &error);
   if (error)
   {
     if (table->in_use->abort_on_warning)