From 8b077c2b9fb9fab697a5136db22e1695da3c6ccb Mon Sep 17 00:00:00 2001
From: unknown <jimw@mysql.com>
Date: Thu, 13 Jan 2005 00:41:45 +0100
Subject: [PATCH 1/2] Fix conversion of floating point values to character
 fields when the absolute value of the float is less than 1, and also fix
 calculation of length for negative values. (Bug #7774)

sql/field.cc:
  Fix handling of negative values and fabs(values> < 1 in Field_str::store
mysql-test/r/type_float.result:
  Add results
mysql-test/r/type_float.result.es:
  Add results
mysql-test/t/type_float.test:
  Add test for conversion of floats to character field
---
 mysql-test/r/type_float.result    | 15 +++++++++++++++
 mysql-test/r/type_float.result.es | 15 +++++++++++++++
 mysql-test/t/type_float.test      | 10 ++++++++++
 sql/field.cc                      | 13 ++++++++++---
 4 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/mysql-test/r/type_float.result b/mysql-test/r/type_float.result
index 9dd92c13c98..530eb32f77d 100644
--- a/mysql-test/r/type_float.result
+++ b/mysql-test/r/type_float.result
@@ -179,3 +179,18 @@ f
 9.999
 9.999
 drop table if exists t1;
+create table t1 (c char(20));
+insert into t1 values (5e-28);
+select * from t1;
+c
+5e-28
+drop table t1;
+create table t1 (c char(6));
+insert into t1 values (2e5),(2e6),(2e-4),(2e-5);
+select * from t1;
+c
+200000
+2e+06
+0.0002
+2e-05
+drop table t1;
diff --git a/mysql-test/r/type_float.result.es b/mysql-test/r/type_float.result.es
index 64d9be7e30f..b93539b6bea 100644
--- a/mysql-test/r/type_float.result.es
+++ b/mysql-test/r/type_float.result.es
@@ -179,3 +179,18 @@ f
 9.999
 9.999
 drop table if exists t1;
+create table t1 (c char(20));
+insert into t1 values (5e-28);
+select * from t1;
+c
+5e-28
+drop table t1;
+create table t1 (c char(6));
+insert into t1 values (2e5),(2e6),(2e-4),(2e-5);
+select * from t1;
+c
+200000
+2e+06
+0.0002
+2e-05
+drop table t1;
diff --git a/mysql-test/t/type_float.test b/mysql-test/t/type_float.test
index 3fe3afa3fac..69cdeaa32a9 100644
--- a/mysql-test/t/type_float.test
+++ b/mysql-test/t/type_float.test
@@ -103,3 +103,13 @@ create table t1 (f double(4,3));
 insert into t1 values (-11.0),(-11),("-11"),(11.0),(11),("11");
 select * from t1;
 drop table if exists t1;
+
+# Check conversion of floats to character field (Bug #7774)
+create table t1 (c char(20));
+insert into t1 values (5e-28);
+select * from t1;
+drop table t1;
+create table t1 (c char(6));
+insert into t1 values (2e5),(2e6),(2e-4),(2e-5);
+select * from t1;
+drop table t1;
diff --git a/sql/field.cc b/sql/field.cc
index e2c11cc7372..2f2115e55dd 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -4301,13 +4301,20 @@ int Field_str::store(double nr)
   char buff[DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE];
   uint length;
   bool use_scientific_notation= TRUE;
-  use_scientific_notation= TRUE;
-  if (field_length < 32 && fabs(nr) < log_10[field_length]-1)
+  /*
+    Check fabs(nr) against longest value that can be stored in field,
+    which depends on whether the value is < 1 or not, and negative or not
+  */
+  double anr= fabs(nr);
+  int neg= (nr < 0.0) ? 1 : 0;
+  if (field_length < 32 &&
+      (anr < 1.0 ? anr > 1/(log_10[max(0,field_length-neg-2)]) /* -2 for "0." */
+                 : anr < log_10[field_length-neg]-1))
     use_scientific_notation= FALSE;
 
   length= (uint) my_sprintf(buff, (buff, "%-.*g",
                                    (use_scientific_notation ?
-                                    max(0, (int)field_length-5) :
+                                    max(0, (int)field_length-neg-5) :
                                     field_length),
                                    nr));
   /*

From 7682d6c9cfa7081dc88b744d1a4f343367309c2b Mon Sep 17 00:00:00 2001
From: unknown <jimw@mysql.com>
Date: Thu, 13 Jan 2005 00:52:19 +0100
Subject: [PATCH 2/2] Small fix for Field_str::store() to avoid trying to read
 past beginning of log_10 array.

sql/field.cc:
  Avoid pointless calculation for really short fields, and what could be
  an attempt to access outside the bounds of the log_10 array.
---
 sql/field.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sql/field.cc b/sql/field.cc
index 2f2115e55dd..fec65438e4d 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -4307,7 +4307,7 @@ int Field_str::store(double nr)
   */
   double anr= fabs(nr);
   int neg= (nr < 0.0) ? 1 : 0;
-  if (field_length < 32 &&
+  if (field_length > 4 && field_length < 32 &&
       (anr < 1.0 ? anr > 1/(log_10[max(0,field_length-neg-2)]) /* -2 for "0." */
                  : anr < log_10[field_length-neg]-1))
     use_scientific_notation= FALSE;