Bug#16194302: SUPPORT FOR FLOATING-POINT SYSTEM VARIABLES

              USING THE PLUGIN INTERFACE.

ISSUE: No support for floating-point plugin
       system variables.

SOLUTION: Allowing plugins to define and expose floating-point
          system variables of type double. MYSQL_SYSVAR_DOUBLE
          and MYSQL_THDVAR_DOUBLE are added.

ISSUE: Fractional part of the def, min, max values of system
       variables are ignored.

SOLUTION: Adding functions that are used to store the raw
          representation of a double in the raw bits of unsigned
          longlong in a way that the binary representation
          remains the same.

1 files changed, 38 insertions, 5 deletions

diff --git a/mysys/my_getopt.c b/mysys/my_getopt.c
index adee17ba3d1..8575fde0ca9 100644
--- a/mysys/my_getopt.c
+++ b/mysys/my_getopt.c
@@ -90,6 +90,35 @@ void my_getopt_register_get_addr(my_getopt_value func_addr)
   getopt_get_addr= func_addr;
 }
 
+union ull_dbl
+{
+  ulonglong ull;
+  double dbl;
+};
+
+/**
+  Returns an ulonglong value containing a raw
+  representation of the given double value.
+*/
+ulonglong getopt_double2ulonglong(double v)
+{
+  union ull_dbl u;
+  u.dbl= v;
+  compile_time_assert(sizeof(ulonglong) >= sizeof(double));
+  return u.ull;
+}
+
+/**
+  Returns the double value which corresponds to
+  the given raw representation.
+*/
+double getopt_ulonglong2double(ulonglong v)
+{
+  union ull_dbl u;
+  u.ull= v;
+  return u.dbl;
+}
+
 /**
   Handle command line options.
   Sort options.
@@ -1044,14 +1073,18 @@ double getopt_double_limit_value(double num, const struct my_option *optp,
 {
   my_bool adjusted= FALSE;
   double old= num;
-  if (optp->max_value && num > (double) optp->max_value)
+  double min, max;
+
+  max= getopt_ulonglong2double(optp->max_value);
+  min= getopt_ulonglong2double(optp->min_value);
+  if (max && num > max)
   {
-    num= (double) optp->max_value;
+    num= max;
     adjusted= TRUE;
   }
-  if (num < (double) optp->min_value)
+  if (num < min)
   {
-    num= (double) optp->min_value;
+    num= min;
     adjusted= TRUE;
   }
   if (fix)
@@ -1134,7 +1167,7 @@ static void init_one_value(const struct my_option *option, void *variable,
     *((ulonglong*) variable)= (ulonglong) value;
     break;
   case GET_DOUBLE:
-    *((double*) variable)= ulonglong2double(value);
+    *((double*) variable)= getopt_ulonglong2double(value);
     break;
   case GET_STR:
     /*