Make strtod respect the rounding mode (bug 14518).

3 files changed, 152 insertions, 52 deletions

diff --git a/stdlib/Makefile b/stdlib/Makefile
index dfc5eaf97b..c730b47433 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -150,3 +150,4 @@ else
 link-libm = $(common-objpfx)math/libm.a
 endif
 $(objpfx)bug-getcontext: $(link-libm)
+$(objpfx)tst-strtod-round: $(link-libm)
diff --git a/stdlib/strtod_l.c b/stdlib/strtod_l.c
index ccd117a9f1..95f13e40a2 100644
--- a/stdlib/strtod_l.c
+++ b/stdlib/strtod_l.c
@@ -61,6 +61,7 @@ extern unsigned long long int ____strtoull_l_internal (const char *, char **,
 #include <stdlib.h>
 #include <string.h>
 #include <stdint.h>
+#include <rounding-mode.h>
 
 /* The gmp headers need some configuration frobs.  */
 #define HAVE_ALLOCA 1
@@ -126,6 +127,8 @@ extern unsigned long long int ____strtoull_l_internal (const char *, char **,
 #define	MIN_EXP		PASTE(FLT,_MIN_EXP)
 #define MAX_10_EXP	PASTE(FLT,_MAX_10_EXP)
 #define MIN_10_EXP	PASTE(FLT,_MIN_10_EXP)
+#define MAX_VALUE	PASTE(FLT,_MAX)
+#define MIN_VALUE	PASTE(FLT,_MIN)
 
 /* Extra macros required to get FLT expanded before the pasting.  */
 #define PASTE(a,b)	PASTE1(a,b)
@@ -172,6 +175,34 @@ extern const mp_limb_t _tens_in_limb[MAX_DIG_PER_LIMB + 1];
 	memcpy (dst, src, (dst##size = src##size) * sizeof (mp_limb_t))
 
 
+/* Set errno and return an overflowing value with sign specified by
+   NEGATIVE.  */
+static FLOAT
+overflow_value (int negative)
+{
+  __set_errno (ERANGE);
+#if FLT_EVAL_METHOD != 0
+  volatile
+#endif
+  FLOAT result = (negative ? -MAX_VALUE : MAX_VALUE) * MAX_VALUE;
+  return result;
+}
+
+
+/* Set errno and return an underflowing value with sign specified by
+   NEGATIVE.  */
+static FLOAT
+underflow_value (int negative)
+{
+  __set_errno (ERANGE);
+#if FLT_EVAL_METHOD != 0
+  volatile
+#endif
+  FLOAT result = (negative ? -MIN_VALUE : MIN_VALUE) * MIN_VALUE;
+  return result;
+}
+
+
 /* Return a floating point number of the needed type according to the given
    multi-precision number after possible rounding.  */
 static FLOAT
@@ -181,10 +212,7 @@ round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
   if (exponent < MIN_EXP - 1)
     {
       if (exponent < MIN_EXP - 1 - MANT_DIG)
-	{
-	  __set_errno (ERANGE);
-	  return negative ? -0.0 : 0.0;
-	}
+	return underflow_value (negative);
 
       mp_size_t shift = MIN_EXP - 1 - exponent;
 
@@ -237,9 +265,14 @@ round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
   if (exponent > MAX_EXP)
     goto overflow;
 
-  if ((round_limb & (((mp_limb_t) 1) << round_bit)) != 0
-      && (more_bits || (retval[0] & 1) != 0
-	  || (round_limb & ((((mp_limb_t) 1) << round_bit) - 1)) != 0))
+  int mode = get_rounding_mode ();
+
+  if (round_away (negative,
+		  (retval[0] & 1) != 0,
+		  (round_limb & (((mp_limb_t) 1) << round_bit)) != 0,
+		  (more_bits
+		   || (round_limb & ((((mp_limb_t) 1) << round_bit) - 1)) != 0),
+		  mode))
     {
       mp_limb_t cy = __mpn_add_1 (retval, retval, RETURN_LIMB_SIZE, 1);
 
@@ -263,7 +296,7 @@ round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
 
   if (exponent > MAX_EXP)
   overflow:
-    return negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL;
+    return overflow_value (negative);
 
   return MPN2FLOAT (retval, exponent, negative);
 }
@@ -914,9 +947,9 @@ ____STRTOF_INTERNAL (nptr, endptr, group, loc)
 		  else
 		    {
 		      /* Overflow or underflow.  */
-		      __set_errno (ERANGE);
-		      result = (exp_negative ? (negative ? -0.0 : 0.0) :
-				negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL);
+		      result = (exp_negative
+				? underflow_value (negative)
+				: overflow_value (negative));
 		    }
 
 		  /* Accept all following digits as part of the exponent.  */
@@ -1112,16 +1145,10 @@ ____STRTOF_INTERNAL (nptr, endptr, group, loc)
   }
 
   if (__builtin_expect (exponent > MAX_10_EXP + 1 - (intmax_t) int_no, 0))
-    {
-      __set_errno (ERANGE);
-      return negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL;
-    }
+    return overflow_value (negative);
 
   if (__builtin_expect (exponent < MIN_10_EXP - (DIG + 1), 0))
-    {
-      __set_errno (ERANGE);
-      return negative ? -0.0 : 0.0;
-    }
+    return underflow_value (negative);
 
   if (int_no > 0)
     {
@@ -1182,10 +1209,7 @@ ____STRTOF_INTERNAL (nptr, endptr, group, loc)
       /* Now we know the exponent of the number in base two.
 	 Check it against the maximum possible exponent.  */
       if (__builtin_expect (bits > MAX_EXP, 0))
-	{
-	  __set_errno (ERANGE);
-	  return negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL;
-	}
+	return overflow_value (negative);
 
       /* We have already the first BITS bits of the result.  Together with
 	 the information whether more non-zero bits follow this is enough
diff --git a/stdlib/tst-strtod-round.c b/stdlib/tst-strtod-round.c
index c6ad126873..76385a94d3 100644
--- a/stdlib/tst-strtod-round.c
+++ b/stdlib/tst-strtod-round.c
@@ -17,6 +17,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <fenv.h>
 #include <float.h>
 #include <math.h>
 #include <stdbool.h>
@@ -24,21 +25,32 @@
 #include <stdlib.h>
 #include <string.h>
 
-struct test {
-  const char *s;
+struct test_results {
   float f;
   double d;
-  bool ld_ok;
   long double ld;
 };
 
+struct test {
+  const char *s;
+  bool ld_ok;
+  struct test_results rd, rn, rz, ru;
+};
+
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 # define TEST(s, fd, fn, fz, fu, dd, dn, dz, du, ld53d, ld53n, ld53z, ld53u,  \
 	      ld64id, ld64in, ld64iz, ld64iu,				      \
 	      ld64md, ld64mn, ld64mz, ld64mu,				      \
 	      ld106exact, ld106d, ld106n, ld106z, ld106u,		      \
 	      ld113d, ld113n, ld113z, ld113u)				      \
-  { s, fn, dn, true, ld53n }
+  {									\
+    s,									\
+    true,								\
+    { fd, dd, ld53d },							\
+    { fn, dn, ld53n },							\
+    { fz, dz, ld53z },							\
+    { fu, du, ld53u }							\
+  }
 #elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 && LDBL_MIN_EXP == -16381
 /* This is for the Intel extended float format.  */
 # define TEST(s, fd, fn, fz, fu, dd, dn, dz, du, ld53d, ld53n, ld53z, ld53u,  \
@@ -46,7 +58,14 @@ struct test {
 	      ld64md, ld64mn, ld64mz, ld64mu,				      \
 	      ld106exact, ld106d, ld106n, ld106z, ld106u,		      \
 	      ld113d, ld113n, ld113z, ld113u)				      \
-  { s, fn, dn, true, ld64in }
+  {									\
+    s,									\
+    true,								\
+    { fd, dd, ld64id },							\
+    { fn, dn, ld64in },							\
+    { fz, dz, ld64iz },							\
+    { fu, du, ld64iu }							\
+  }
 #elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 && LDBL_MIN_EXP == -16382
 /* This is for the Motorola extended float format.  */
 # define TEST(s, fd, fn, fz, fu, dd, dn, dz, du, ld53d, ld53n, ld53z, ld53u,  \
@@ -54,21 +73,42 @@ struct test {
 	      ld64md, ld64mn, ld64mz, ld64mu,				      \
 	      ld106exact, ld106d, ld106n, ld106z, ld106u,		      \
 	      ld113d, ld113n, ld113z, ld113u)				      \
-  { s, fn, dn, true, ld64mn }
+  {									\
+    s,									\
+    true,								\
+    { fd, dd, ld64md },							\
+    { fn, dn, ld64mn },							\
+    { fz, dz, ld64mz },							\
+    { fu, du, ld64mu }							\
+  }
 #elif LDBL_MANT_DIG == 106 && LDBL_MAX_EXP == 1024
 # define TEST(s, fd, fn, fz, fu, dd, dn, dz, du, ld53d, ld53n, ld53z, ld53u,  \
 	      ld64id, ld64in, ld64iz, ld64iu,				      \
 	      ld64md, ld64mn, ld64mz, ld64mu,				      \
 	      ld106exact, ld106d, ld106n, ld106z, ld106u,		      \
 	      ld113d, ld113n, ld113z, ld113u)				      \
-  { s, fn, dn, ld106exact, ld106n }
+  {									\
+    s,									\
+    ld106exact,								\
+    { fd, dd, ld106d },							\
+    { fn, dn, ld106n },							\
+    { fz, dz, ld106z },							\
+    { fu, du, ld106u }							\
+  }
 #elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
 # define TEST(s, fd, fn, fz, fu, dd, dn, dz, du, ld53d, ld53n, ld53z, ld53u,  \
 	      ld64id, ld64in, ld64iz, ld64iu,				      \
 	      ld64md, ld64mn, ld64mz, ld64mu,				      \
 	      ld106exact, ld106d, ld106n, ld106z, ld106u,		      \
 	      ld113d, ld113n, ld113z, ld113u)				      \
-  { s, fn, dn, true, ld113n }
+  {									\
+    s,									\
+    true,								\
+    { fd, dd, ld113d },							\
+    { fn, dn, ld113n },							\
+    { fz, dz, ld113z },							\
+    { fu, du, ld113u }							\
+  }
 #else
 # error "unknown long double format"
 #endif
@@ -6819,38 +6859,73 @@ static const struct test tests[] = {
 };
 
 static int
+test_in_one_mode (const char *s, const struct test_results *expected,
+		  bool ld_ok, const char *mode_name)
+{
+  int result = 0;
+  float f = strtof (s, NULL);
+  double d = strtod (s, NULL);
+  long double ld = strtold (s, NULL);
+  if (f != expected->f
+      || copysignf (1.0f, f) != copysignf (1.0f, expected->f))
+    {
+      printf ("strtof (%s) returned %a not %a (%s)\n", s, f,
+	      expected->f, mode_name);
+      result = 1;
+    }
+  if (d != expected->d
+      || copysign (1.0, d) != copysign (1.0, expected->d))
+    {
+      printf ("strtod (%s) returned %a not %a (%s)\n", s, d,
+	      expected->d, mode_name);
+      result = 1;
+    }
+  if (ld != expected->ld
+      || copysignl (1.0L, ld) != copysignl (1.0L, expected->ld))
+    {
+      printf ("strtold (%s) returned %La not %La (%s)\n", s, ld,
+	      expected->ld, mode_name);
+      if (ld_ok)
+	result = 1;
+      else
+	printf ("ignoring this inexact long double result\n");
+    }
+  return result;
+}
+
+static int
 do_test (void)
 {
+  int save_round_mode = fegetround ();
   int result = 0;
   for (size_t i = 0; i < sizeof (tests) / sizeof (tests[0]); i++)
     {
-      float f = strtof (tests[i].s, NULL);
-      double d = strtod (tests[i].s, NULL);
-      long double ld = strtold (tests[i].s, NULL);
-      if (f != tests[i].f
-	  || copysignf (1.0f, f) != copysignf (1.0f, tests[i].f))
+      result |= test_in_one_mode (tests[i].s, &tests[i].rn, tests[i].ld_ok,
+				  "default rounding mode");
+#ifdef FE_DOWNWARD
+      if (!fesetround (FE_DOWNWARD))
 	{
-	  printf ("strtof (%s) returned %a not %a\n", tests[i].s, f,
-		  tests[i].f);
-	  result = 1;
+	  result |= test_in_one_mode (tests[i].s, &tests[i].rd, tests[i].ld_ok,
+				      "FE_DOWNWARD");
+	  fesetround (save_round_mode);
 	}
-      if (d != tests[i].d
-	  || copysign (1.0, d) != copysign (1.0, tests[i].d))
+#endif
+#ifdef FE_TOWARDZERO
+      if (!fesetround (FE_TOWARDZERO))
 	{
-	  printf ("strtod (%s) returned %a not %a\n", tests[i].s, d,
-		  tests[i].d);
-	  result = 1;
+	  result |= test_in_one_mode (tests[i].s, &tests[i].rz, tests[i].ld_ok,
+				      "FE_TOWARDZERO");
+	  fesetround (save_round_mode);
 	}
-      if (ld != tests[i].ld
-	  || copysignl (1.0L, ld) != copysignl (1.0L, tests[i].ld))
+#endif
+#ifdef FE_UPWARD
+      if (!fesetround (FE_UPWARD))
 	{
-	  printf ("strtold (%s) returned %La not %La\n", tests[i].s, ld,
-		  tests[i].ld);
-	  if (tests[i].ld_ok)
-	    result = 1;
-	  else
-	    printf ("ignoring this inexact long double result\n");
+	  result |= test_in_one_mode (tests[i].s, &tests[i].ru, tests[i].ld_ok,
+				      "FE_UPWARD");
+	  fesetround (save_round_mode);
 	}
+#endif
     }
   return result;
 }