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authorPaul E. Murphy <murphyp@linux.vnet.ibm.com>2016-02-29 13:27:36 -0600
committerPaul E. Murphy <murphyp@linux.vnet.ibm.com>2016-03-31 12:14:33 -0500
commit37a4c70bd4c5c74ac562072e450dc02e8cb4c150 (patch)
treec9a631e747dcb7ca4213c93460d7e45d153a0771 /stdio-common
parent830566307f038387ca0af3fd327706a8d1a2f595 (diff)
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Increase internal precision of ldbl-128ibm decimal printf [BZ #19853]
When the signs differ, the precision of the conversion sometimes drops below 106 bits. This strategy is identical to the hexadecimal variant. I've refactored tst-sprintf3 to enable testing a value with more than 30 significant digits in order to demonstrate this failure and its solution. Additionally, this implicitly fixes a typo in the shift quantities when subtracting from the high mantissa to compute the difference.
Diffstat (limited to 'stdio-common')
-rw-r--r--stdio-common/tst-sprintf3.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/stdio-common/tst-sprintf3.c b/stdio-common/tst-sprintf3.c
index cffd1b6..dad216b 100644
--- a/stdio-common/tst-sprintf3.c
+++ b/stdio-common/tst-sprintf3.c
@@ -38,11 +38,11 @@ do_test (void)
# define COMPARE_LDBL(u, v) ((u).l == (v).l)
#endif
-#define TEST(val) \
+#define TEST_N(val, n) \
do \
{ \
u.l = (val); \
- snprintf (buf, sizeof buf, "%.30LgL", u.l); \
+ snprintf (buf, sizeof buf, "%." #n "LgL", u.l); \
if (strcmp (buf, #val) != 0) \
{ \
printf ("Error on line %d: %s != %s\n", __LINE__, buf, #val); \
@@ -50,19 +50,25 @@ do_test (void)
} \
if (sscanf (#val, "%Lg", &v.l) != 1 || !COMPARE_LDBL (u, v)) \
{ \
- printf ("Error sscanf on line %d: %.30Lg != %.30Lg\n", __LINE__, \
- u.l, v.l); \
+ printf ("Error sscanf on line %d: %." #n "Lg != %." #n "Lg\n", \
+ __LINE__, u.l, v.l); \
result = 1; \
} \
/* printf ("%s %Lg %016Lx %016Lx\n", #val, u.l, u.x[0], u.x[1]); */ \
} \
while (0)
+#define TEST(val) TEST_N (val,30)
+
#if LDBL_MANT_DIG >= 106
# if LDBL_MANT_DIG == 106
TEST (2.22507385850719347803989925739e-308L);
TEST (2.22507385850719397210554509863e-308L);
TEST (2.22507385850720088902458687609e-308L);
+
+ /* Verify precision is not lost for long doubles
+ of the form +1.pN,-1.pM. */
+ TEST_N (3.32306998946228968225951765070082e+35L, 34);
# endif
TEST (2.22507385850720138309023271733e-308L);
TEST (2.22507385850720187715587855858e-308L);