[svn-r9807] Purpose: bug fix

Description: For FreeBSD (sleipnir), when GNU compilers do conversion from
unsigned long long to long double, the last 2 bytes of mantissa are lost.
The impact of precision loss isn't significant.

Solution:  Detect this case on FreeBSD in configure, ignore it in dtypes.c
test instead of return failure.

Platforms tested: sleipnir, fuss, modi4.  These systems are mainly concerned.

4 files changed, 164 insertions, 2 deletions

diff --git a/configure b/configure
index 91c41c7..708ff29 100755
--- a/configure
+++ b/configure
@@ -33808,7 +33808,7 @@ else
         unsigned long long l2 = (unsigned long long)d1;
         unsigned long long l3 = (unsigned long long)d2;
         unsigned long long l4;
-        unsigned long long l5 = 0x7fffffffffffffffLLU;
+        unsigned long long l5 = 0x7fffffffffffffffULL;
         int           ret = 0;
 
         if(l1 <= l5 || l2 <= l5 || l3 <= l5)
@@ -33883,6 +33883,94 @@ else
 echo "${ECHO_T}no" >&6
 fi
 
+echo "$as_me:$LINENO: checking if converting unsigned long long to long double with precision work" >&5
+echo $ECHO_N "checking if converting unsigned long long to long double with precision work... $ECHO_C" >&6
+if test "${hdf5_cv_ullong_to_ldouble_precision_works+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  if test "$cross_compiling" = yes; then
+  { { echo "$as_me:$LINENO: error: cannot run test program while cross compiling" >&5
+echo "$as_me: error: cannot run test program while cross compiling" >&2;}
+   { (exit 1); exit 1; }; }
+else
+  cat >conftest.$ac_ext <<_ACEOF
+#line $LINENO "configure"
+#include "confdefs.h"
+
+    int main(void)
+    {
+        unsigned long long l = 0xa601e80bda85fcefULL;
+        long double ld;
+        unsigned char *c1, *c2;
+        int endian, size;
+        int tst_value = 1;
+        int i;
+        int           ret = 0;
+
+        /* Determine this system's endianess */
+        c1 = (unsigned char*)calloc(1, sizeof(int));
+        memcpy(c1, &tst_value, sizeof(int));
+        if(c1[0]==1)
+            endian = 0;  /* little endian */
+        else
+            endian = 1;  /* big endian */
+
+        memset(&ld, 0, 12);
+        ld = (long double)l;
+
+        size = sizeof(long double);
+        c2 = (unsigned char*)malloc(size);
+        memcpy(c2, &ld, size);
+
+        /* Test if the last 2 bytes of mantissa are lost.  Mainly for FreeBSD on Intel
+         * architecture(sleipnir) where it happens. */
+        if(endian==0 && c2[0]==0 && c2[1]==0) /*little endian*/
+            ret = 1;
+
+        free(c1);
+        free(c2);
+done:
+        exit(ret);
+    }
+
+_ACEOF
+rm -f conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  hdf5_cv_ullong_to_ldouble_precision_works=yes
+else
+  echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+cat conftest.$ac_ext >&5
+( exit $ac_status )
+hdf5_cv_ullong_to_ldouble_precision_works=no
+fi
+rm -f core core.* *.core conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+fi
+
+
+if test ${hdf5_cv_ullong_to_ldouble_precision_works} = "yes"; then
+
+cat >>confdefs.h <<\_ACEOF
+#define ULLONG_TO_LDOUBLE_PRECISION_WORKS 1
+_ACEOF
+
+  echo "$as_me:$LINENO: result: yes" >&5
+echo "${ECHO_T}yes" >&6
+else
+  echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6
+fi
+
 
 H5_VERSION="`cut -d' ' -f3 $srcdir/README.txt | head -1`"
 
diff --git a/configure.in b/configure.in
index f668717..3dfacbc 100644
--- a/configure.in
+++ b/configure.in
@@ -2685,7 +2685,7 @@ AC_CACHE_VAL([hdf5_cv_fp_to_ullong_right_maximum],
         unsigned long long l2 = (unsigned long long)d1;
         unsigned long long l3 = (unsigned long long)d2;
         unsigned long long l4;
-        unsigned long long l5 = 0x7fffffffffffffffLLU;
+        unsigned long long l5 = 0x7fffffffffffffffULL;
         int           ret = 0;
 
         if(l1 <= l5 || l2 <= l5 || l3 <= l5) 
@@ -2728,6 +2728,61 @@ else
 fi
 
 dnl ----------------------------------------------------------------------
+dnl Set the flag to indicate that the machine can convert from
+dnl 'unsigned long long' to 'long double' without precision loss.
+dnl (This flag should be set for all machines, except for FreeBSD(sleipnir)
+dnl where the last 2 bytes of mantissa are lost when compiler tries to do 
+dnl the conversion.)
+dnl
+AC_MSG_CHECKING([if converting unsigned long long to long double with precision work])
+AC_CACHE_VAL([hdf5_cv_ullong_to_ldouble_precision_works],
+    [AC_TRY_RUN([
+    int main(void)
+    {
+        unsigned long long l = 0xa601e80bda85fcefULL;
+        long double ld;
+        unsigned char *c1, *c2;
+        int endian, size;
+        int tst_value = 1; 
+        int i;
+        int           ret = 0;
+
+        /* Determine this system's endianess */
+        c1 = (unsigned char*)calloc(1, sizeof(int));
+        memcpy(c1, &tst_value, sizeof(int));
+        if(c1[0]==1)
+            endian = 0;  /* little endian */
+        else 
+            endian = 1;  /* big endian */
+             
+        memset(&ld, 0, 12); 
+        ld = (long double)l;
+
+        size = sizeof(long double);
+        c2 = (unsigned char*)malloc(size);
+        memcpy(c2, &ld, size);
+
+        /* Test if the last 2 bytes of mantissa are lost.  Mainly for FreeBSD on Intel
+         * architecture(sleipnir) where it happens. */        
+        if(endian==0 && c2[0]==0 && c2[1]==0) /*little endian*/
+            ret = 1;
+        
+        free(c1);
+        free(c2);
+done:
+        exit(ret);
+    }
+    ], [hdf5_cv_ullong_to_ldouble_precision_works=yes], [hdf5_cv_ullong_to_ldouble_precision_works=no],)])
+
+if test ${hdf5_cv_ullong_to_ldouble_precision_works} = "yes"; then
+  AC_DEFINE([ULLONG_TO_LDOUBLE_PRECISION_WORKS], [1],
+            [Define if your system can convert unsigned long long to long double with correct precision.])
+  AC_MSG_RESULT([yes])
+else
+  AC_MSG_RESULT([no])
+fi
+
+dnl ----------------------------------------------------------------------
 dnl Set some variables for general configuration information to be saved
 dnl and installed with the libraries.
 dnl
diff --git a/src/H5config.h.in b/src/H5config.h.in
index d7f27f9..aa30b7b 100644
--- a/src/H5config.h.in
+++ b/src/H5config.h.in
@@ -545,6 +545,10 @@
    casts. */
 #undef ULLONG_TO_FP_CAST_WORKS
 
+/* Define if your system can convert unsigned long long to long double with
+   correct precision. */
+#undef ULLONG_TO_LDOUBLE_PRECISION_WORKS
+
 /* Define if the HDF5 v1.6 compatibility functions are to be compiled in */
 #undef WANT_H5_V1_6_COMPAT
 
diff --git a/test/dtypes.c b/test/dtypes.c
index dd94193..c6d6a57 100644
--- a/test/dtypes.c
+++ b/test/dtypes.c
@@ -5849,6 +5849,21 @@ test_conv_int_float(const char *name, hid_t src, hid_t dst)
             }
 #endif /*end H5_FP_TO_ULLONG_BOTTOM_BIT_WORKS*/
 
+/* For GNU compilers on FreeBSD(sleipnir), during conversion from 'unsigned long long'
+ * to 'long double', the last 2 bytes of mantissa are lost.  But this loss seems
+ * acceptable.  We allow it go through instead of fail it.
+ */
+#ifndef H5_ULLONG_TO_LDOUBLE_PRECISION_WORKS
+            if(src_type==INT_ULLONG && dst_type==FLT_LDOUBLE) {
+                long double tmp_s, tmp_h;
+                HDmemcpy(&tmp_s,&buf[j*dst_size],sizeof(long double));
+                HDmemcpy(&tmp_h,&hw[0],sizeof(long double));
+                /*Don't compare the last 2 bytes of mantissa*/
+                if(!HDmemcmp(&tmp_s+2, &tmp_h+2, sizeof(long double)-2))
+                    continue; /*no error*/
+            }
+#endif /*end H5_ULLONG_TO_LDOUBLE_PRECISION_WORKS*/
+            
 	    /* Print errors */
 	    if (0==fails_this_test++)
                 H5_FAILED();