Cleanup isinf() portability checks

Original problem reported by Wlad: re-compilation of 10.3 on top of 10.2
build would cache undefined HAVE_ISINF from 10.2, whereas it is expected
to be 1 in 10.3.

std::isinf() seem to be available on all supported platforms.
(cherry picked from commit bc469a0b)

configure.cmake

@@ -477,16 +477,6 @@ ENDIF()
 CHECK_SYMBOL_EXISTS(log2  math.h HAVE_LOG2)
 CHECK_SYMBOL_EXISTS(rint  math.h HAVE_RINT)
 
-# isinf() prototype not found on Solaris
-CHECK_CXX_SOURCE_COMPILES(
-"#include  <math.h>
-int main() { 
-  isinf(0.0); 
-  return 0;
-}" HAVE_ISINF)
-
-
-
 #
 # Test for endianess
 #

include/my_global.h

@@ -826,12 +826,6 @@ inline unsigned long long my_double2ulonglong(double d)
 static inline bool isfinite(double x) { return std::isfinite(x); }
 #endif /* isfinite */
 
-#ifdef HAVE_ISINF
-#define my_isinf(X) isinf(X)
-#else /* !HAVE_ISINF */
-#define my_isinf(X) (!finite(X) && !isnan(X))
-#endif
-
 /* Define missing math constants. */
 #ifndef M_PI
 #define M_PI 3.14159265358979323846

sql/field.cc

@@ -4843,7 +4843,7 @@ int truncate_double(double *nr, uint field_length, uint dec,
     max_value-= 1.0 / log_10[dec];
 
     /* Check for infinity so we don't get NaN in calculations */
-    if (!my_isinf(res))
+    if (!std::isinf(res))
     {
       double tmp= rint((res - floor(res)) * log_10[dec]) / log_10[dec];
       res= floor(res) + tmp;

sql/item_func.cc

@@ -2553,12 +2553,12 @@ double my_double_round(double value, longlong dec, bool dec_unsigned,
   volatile double value_div_tmp= value / tmp;
   volatile double value_mul_tmp= value * tmp;
 
-  if (!dec_negative && my_isinf(tmp)) // "dec" is too large positive number
+  if (!dec_negative && std::isinf(tmp)) // "dec" is too large positive number
     return value;
 
-  if (dec_negative && my_isinf(tmp))
+  if (dec_negative && std::isinf(tmp))
     tmp2= 0.0;
-  else if (!dec_negative && my_isinf(value_mul_tmp))
+  else if (!dec_negative && std::isinf(value_mul_tmp))
     tmp2= value;
   else if (truncate)
   {

sql/item_sum.cc

@@ -1808,7 +1808,7 @@ double Item_sum_std::val_real()
 {
   DBUG_ASSERT(fixed == 1);
   double nr= Item_sum_variance::val_real();
-  if (isnan(nr))
+  if (std::isnan(nr))
   {
     /*
       variance_fp_recurrence_next() can overflow in some cases and return "nan":
@@ -1820,7 +1820,7 @@ double Item_sum_std::val_real()
     null_value= true; // Convert "nan" to NULL
     return 0;
   }
-  if (my_isinf(nr))
+  if (std::isinf(nr))
     return DBL_MAX;
   DBUG_ASSERT(nr >= 0.0);
   return sqrt(nr);