Fix rounding before exponent for "g/G"

Author: R3G3N3R4T0R

src/fmtcore.jl

@@ -333,7 +333,8 @@ end
 
 function _pfmt_g(out::IO, fs::FormatSpec, x::AbstractFloat)
     # Branch according to the exponent
-    expnt = x == 0 ? 0 : floor(Int, log10(abs(x)) )
+    ax = round(abs(x) ;sigdigits=fs.prec)
+    expnt = ax == 0 ? 0 : floor(Int, log10(ax) )
     if -4 <= expnt < fs.prec
         newprec = fs.prec - expnt - 1
         _pfmt_f(out, FormatSpec(fs ;prec=newprec), x)