Merge pull request #19373 from JuliaLang/sb/ndigits

fix overflow in ndigits0z

Author: StefanKarpinski

base/intfuncs.jl

@@ -314,8 +314,6 @@ function ndigits0z(x::UInt128)
 end
 ndigits0z(x::Integer) = ndigits0z(unsigned(abs(x)))
 
-const ndigits_max_mul = Core.sizeof(Int) == 4 ? 69000000 : 290000000000000000
-
 function ndigits0znb(n::Signed, b::Int)
     d = 0
     while n != 0
@@ -326,23 +324,24 @@ function ndigits0znb(n::Signed, b::Int)
 end
 
 function ndigits0z(n::Unsigned, b::Int)
+    b < 0   && return ndigits0znb(signed(n), b)
+    b == 2  && return sizeof(n)<<3 - leading_zeros(n)
+    b == 8  && return (sizeof(n)<<3 - leading_zeros(n) + 2) ÷ 3
+    b == 16 && return sizeof(n)<<1 - leading_zeros(n)>>2
+    b == 10 && return ndigits0z(n)
+
     d = 0
-    if b < 0
-        d = ndigits0znb(signed(n), b)
-    else
-        b == 2  && return (sizeof(n)<<3-leading_zeros(n))
-        b == 8  && return div((sizeof(n)<<3)-leading_zeros(n)+2,3)
-        b == 16 && return (sizeof(n)<<1)-(leading_zeros(n)>>2)
-        b == 10 && return ndigits0z(n)
-        while ndigits_max_mul < n
-            n = div(n,b)
-            d += 1
-        end
-        m = 1
-        while m <= n
-            m *= b
-            d += 1
-        end
+    while n > typemax(Int)
+        n = div(n,b)
+        d += 1
+    end
+    n = div(n,b)
+    d += 1
+
+    m = 1
+    while m <= n
+        m *= b
+        d += 1
     end
     return d
 end

test/intfuncs.jl

@@ -89,6 +89,9 @@ let n = rand(Int)
 end
 @test ndigits(Int8(5)) == ndigits(5)
 
+# issue #19367
+@test ndigits(Int128(2)^64, 256) == 9
+
 @test bin('3') == "110011"
 @test bin('3',7) == "0110011"
 @test bin(3) == "11"