Detect pseudo-denormals on x86 even when cross-compiling.

* lib/isnan.c (rpl_isnanl) [!KNOWN_EXPBIT0_LOCATION
&& USE_LONG_DOUBLE && x86]: Add one more check to filter out
invalid bit patterns that happen to satisfy ==.

Signed-off-by: Eric Blake <ebb9@byu.net>

diff --git a/ChangeLog b/ChangeLog
index ed8799b..127f9a5 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2007-12-11  Eric Blake  <ebb9@byu.net>
 
+       Detect pseudo-denormals on x86 even when cross-compiling.
+       * lib/isnan.c (rpl_isnanl) [!KNOWN_EXPBIT0_LOCATION
+       && USE_LONG_DOUBLE && x86]: Add one more check to filter out
+       invalid bit patterns that happen to satisfy ==.
+
        Avoid link failures with separate libtests.a.
        * gnulib-tool (func_emit_tests_Makefile_am): Also list local_ldadd
        last, to satisfy circular dependencies.

diff --git a/lib/isnan.c b/lib/isnan.c
index 4add6a2..182a7bd 100644 (file)
--- a/lib/isnan.c
+++ b/lib/isnan.c
@@ -140,7 +140,19 @@ FUNC (DOUBLE x)
   /* The configuration did not find sufficient information.  Give up about
      the signaling NaNs, handle only the quiet NaNs.  */
   if (x == x)
-    return 0;
+    {
+# if defined USE_LONG_DOUBLE && ((defined __ia64 && LDBL_MANT_DIG == 64) || (defined __x86_64__ || defined __amd64__) || (defined __i386 || defined __i386__ || defined _I386 || defined _M_IX86 || defined _X86_))
+      /* Detect any special bit patterns that pass ==; see comment above.  */
+      memory_double m1;
+      memory_double m2;
+
+      m1.value = x;
+      m2.value = x + 0;
+      if (memcmp (&m1.value, &m2.value, SIZE) != 0)
+        return 1;
+# endif
+      return 0;
+    }
   else
     return 1;
 #endif