fix off-by-one error that caused uninitialized memory read in floatscan

this caused misreading of certain floating point values that are exact
multiples of large powers of ten, unpredictable depending on prior
stack contents.

diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c
index f80db3839ea87ec2d0513f6c4f4bb1eff0aba05e..4b335f5cf4a45b5254f4d471bb34c67501a3ca9c 100644 (file)
--- a/src/internal/floatscan.c
+++ b/src/internal/floatscan.c
@@ -244,7 +244,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po
 
        /* Assemble desired bits into floating point variable */
        for (y=i=0; i<LD_B1B_DIG; i++) {
-               if ((a+i & MASK)==z) x[z=(z+1 & MASK)] = 0;
+               if ((a+i & MASK)==z) x[(z=(z+1 & MASK))-1] = 0;
                y = 1000000000.0L * y + x[a+i & MASK];
        }