fix strtod int optimization in non-nearest rounding mode

the mid-sized integer optimization relies on lnz set up properly
to mark the last non-zero decimal digit, but this was not done
if the non-zero digit lied outside the KMAX digits of the base
10^9 number representation.

so if the fractional part was a very long list of zeros (>2048*9 on
x86) followed by non-zero digits then the integer optimization could
kick in discarding the tiny non-zero fraction which can mean wrong
result on non-nearest rounding mode.

strtof, strtod and strtold were all affected.

diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c
index 80305ee..ae09852 100644 (file)
--- a/src/internal/floatscan.c
+++ b/src/internal/floatscan.c
@@ -110,7 +110,10 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
                        gotdig=1;
                } else {
                        dc++;
-                       if (c!='0') x[KMAX-4] |= 1;
+                       if (c!='0') {
+                               lnz = dc;
+                               x[KMAX-4] |= 1;
+                       }
                }
        }
        if (!gotrad) lrp=dc;