Make printf respect the rounding mode for hex output (bug 5044).

2 files changed, 151 insertions, 13 deletions

diff --git a/stdio-common/printf_fphex.c b/stdio-common/printf_fphex.c
index 1349145..2224196 100644
--- a/stdio-common/printf_fphex.c
+++ b/stdio-common/printf_fphex.c
@@ -28,6 +28,8 @@
 #include <_itoa.h>
 #include <_itowa.h>
 #include <locale/localeinfo.h>
+#include <stdbool.h>
+#include <rounding-mode.h>
 
 /* #define NDEBUG 1*/		/* Undefine this for debugging assertions.  */
 #include <assert.h>
@@ -343,21 +345,33 @@ __printf_fphex (FILE *fp,
 	  --numend;
 	}
 
+      bool do_round_away = false;
+
+      if (precision != -1 && precision < numend - numstr)
+	{
+	  char last_digit = precision > 0 ? numstr[precision - 1] : leading;
+	  char next_digit = numstr[precision];
+	  int last_digit_value = (last_digit >= 'A' && last_digit <= 'F'
+				  ? last_digit - 'A' + 10
+				  : (last_digit >= 'a' && last_digit <= 'f'
+				     ? last_digit - 'a' + 10
+				     : last_digit - '0'));
+	  int next_digit_value = (next_digit >= 'A' && next_digit <= 'F'
+				  ? next_digit - 'A' + 10
+				  : (next_digit >= 'a' && next_digit <= 'f'
+				     ? next_digit - 'a' + 10
+				     : next_digit - '0'));
+	  bool more_bits = ((next_digit_value & 7) != 0
+			    || precision + 1 < numend - numstr);
+	  int rounding_mode = get_rounding_mode ();
+	  do_round_away = round_away (negative, last_digit_value & 1,
+				      next_digit_value >= 8, more_bits,
+				      rounding_mode);
+	}
+
       if (precision == -1)
 	precision = numend - numstr;
-      else if (precision < numend - numstr
-	       && (numstr[precision] > '8'
-		   || (('A' < '0' || 'a' < '0')
-		       && numstr[precision] < '0')
-		   || (numstr[precision] == '8'
-		       && (precision + 1 < numend - numstr
-			   /* Round to even.  */
-			   || (precision > 0
-			       && ((numstr[precision - 1] & 1)
-				   ^ (isdigit (numstr[precision - 1]) == 0)))
-			   || (precision == 0
-			       && ((leading & 1)
-				   ^ (isdigit (leading) == 0)))))))
+      else if (do_round_away)
 	{
 	  /* Round up.  */
 	  int cnt = precision;
diff --git a/stdio-common/tst-printf-round.c b/stdio-common/tst-printf-round.c
index 2bd4607..7cc19c5 100644
--- a/stdio-common/tst-printf-round.c
+++ b/stdio-common/tst-printf-round.c
@@ -68,6 +68,99 @@ test_dec_in_one_mode (double d, const char *fmt, const char *expected,
     }
 }
 
+struct hex_test
+{
+  double d;
+  const char *fmt;
+  const char *rd[4], *rn[4], *rz[4], *ru[4];
+};
+
+static const struct hex_test hex_tests[] =
+  {
+    {
+      0x1.fffffp+4, "%.1a",
+      { "0x1.fp+4", "0x3.fp+3", "0x7.fp+2", "0xf.fp+1" },
+      { "0x2.0p+4", "0x4.0p+3", "0x8.0p+2", "0x1.0p+5" },
+      { "0x1.fp+4", "0x3.fp+3", "0x7.fp+2", "0xf.fp+1" },
+      { "0x2.0p+4", "0x4.0p+3", "0x8.0p+2", "0x1.0p+5" }
+    },
+    {
+      -0x1.fffffp+4, "%.1a",
+      { "-0x2.0p+4", "-0x4.0p+3", "-0x8.0p+2", "-0x1.0p+5" },
+      { "-0x2.0p+4", "-0x4.0p+3", "-0x8.0p+2", "-0x1.0p+5" },
+      { "-0x1.fp+4", "-0x3.fp+3", "-0x7.fp+2", "-0xf.fp+1" },
+      { "-0x1.fp+4", "-0x3.fp+3", "-0x7.fp+2", "-0xf.fp+1" }
+    },
+    {
+      0x1.88p+4, "%.1a",
+      { "0x1.8p+4", "0x3.1p+3", "0x6.2p+2", "0xc.4p+1" },
+      { "0x1.8p+4", "0x3.1p+3", "0x6.2p+2", "0xc.4p+1" },
+      { "0x1.8p+4", "0x3.1p+3", "0x6.2p+2", "0xc.4p+1" },
+      { "0x1.9p+4", "0x3.1p+3", "0x6.2p+2", "0xc.4p+1" }
+    },
+    {
+      -0x1.88p+4, "%.1a",
+      { "-0x1.9p+4", "-0x3.1p+3", "-0x6.2p+2", "-0xc.4p+1" },
+      { "-0x1.8p+4", "-0x3.1p+3", "-0x6.2p+2", "-0xc.4p+1" },
+      { "-0x1.8p+4", "-0x3.1p+3", "-0x6.2p+2", "-0xc.4p+1" },
+      { "-0x1.8p+4", "-0x3.1p+3", "-0x6.2p+2", "-0xc.4p+1" }
+    },
+    {
+      0x1.78p+4, "%.1a",
+      { "0x1.7p+4", "0x2.fp+3", "0x5.ep+2", "0xb.cp+1" },
+      { "0x1.8p+4", "0x2.fp+3", "0x5.ep+2", "0xb.cp+1" },
+      { "0x1.7p+4", "0x2.fp+3", "0x5.ep+2", "0xb.cp+1" },
+      { "0x1.8p+4", "0x2.fp+3", "0x5.ep+2", "0xb.cp+1" }
+    },
+    {
+      -0x1.78p+4, "%.1a",
+      { "-0x1.8p+4", "-0x2.fp+3", "-0x5.ep+2", "-0xb.cp+1" },
+      { "-0x1.8p+4", "-0x2.fp+3", "-0x5.ep+2", "-0xb.cp+1" },
+      { "-0x1.7p+4", "-0x2.fp+3", "-0x5.ep+2", "-0xb.cp+1" },
+      { "-0x1.7p+4", "-0x2.fp+3", "-0x5.ep+2", "-0xb.cp+1" }
+    },
+    {
+      64.0 / 3.0, "%.1a",
+      { "0x1.5p+4", "0x2.ap+3", "0x5.5p+2", "0xa.ap+1" },
+      { "0x1.5p+4", "0x2.bp+3", "0x5.5p+2", "0xa.bp+1" },
+      { "0x1.5p+4", "0x2.ap+3", "0x5.5p+2", "0xa.ap+1" },
+      { "0x1.6p+4", "0x2.bp+3", "0x5.6p+2", "0xa.bp+1" }
+    },
+    {
+      -64.0 / 3.0, "%.1a",
+      { "-0x1.6p+4", "-0x2.bp+3", "-0x5.6p+2", "-0xa.bp+1" },
+      { "-0x1.5p+4", "-0x2.bp+3", "-0x5.5p+2", "-0xa.bp+1" },
+      { "-0x1.5p+4", "-0x2.ap+3", "-0x5.5p+2", "-0xa.ap+1" },
+      { "-0x1.5p+4", "-0x2.ap+3", "-0x5.5p+2", "-0xa.ap+1" }
+    },
+  };
+
+static int
+test_hex_in_one_mode (double d, const char *fmt, const char *expected[4],
+		      const char *mode_name)
+{
+  char buf[100];
+  int ret = snprintf (buf, sizeof buf, fmt, d);
+  if (ret <= 0 || ret >= (int) sizeof buf)
+    {
+      printf ("snprintf for %a returned %d\n", d, ret);
+      return 1;
+    }
+  if (strcmp (buf, expected[0]) == 0
+      || strcmp (buf, expected[1]) == 0
+      || strcmp (buf, expected[2]) == 0
+      || strcmp (buf, expected[3]) == 0)
+    return 0;
+  else
+    {
+      printf ("snprintf (\"%s\", %a) returned \"%s\" not "
+	      "\"%s\" or \"%s\" or \"%s\" or \"%s\" (%s)\n",
+	      fmt, d, buf, expected[0], expected[1], expected[2], expected[3],
+	      mode_name);
+      return 1;
+    }
+}
+
 static int
 do_test (void)
 {
@@ -103,6 +196,37 @@ do_test (void)
 	}
 #endif
     }
+
+  for (size_t i = 0; i < sizeof (hex_tests) / sizeof (hex_tests[0]); i++)
+    {
+      result |= test_hex_in_one_mode (hex_tests[i].d, hex_tests[i].fmt,
+				      hex_tests[i].rn, "default rounding mode");
+#ifdef FE_DOWNWARD
+      if (!fesetround (FE_DOWNWARD))
+	{
+	  result |= test_hex_in_one_mode (hex_tests[i].d, hex_tests[i].fmt,
+					  hex_tests[i].rd, "FE_DOWNWARD");
+	  fesetround (save_round_mode);
+	}
+#endif
+#ifdef FE_TOWARDZERO
+      if (!fesetround (FE_TOWARDZERO))
+	{
+	  result |= test_hex_in_one_mode (hex_tests[i].d, hex_tests[i].fmt,
+					  hex_tests[i].rz, "FE_TOWARDZERO");
+	  fesetround (save_round_mode);
+	}
+#endif
+#ifdef FE_UPWARD
+      if (!fesetround (FE_UPWARD))
+	{
+	  result |= test_hex_in_one_mode (hex_tests[i].d, hex_tests[i].fmt,
+					  hex_tests[i].ru, "FE_UPWARD");
+	  fesetround (save_round_mode);
+	}
+#endif
+    }
+
   return result;
 }