Fix 64 bit variants. Note undefined behavior

2026-05-20 20:33:10 +02:00
parent c7d175d90f
commit 66dfd956da
1 changed files with 6 additions and 2 deletions
@@ -25,6 +25,10 @@ uc_phi_64(uint64_t N);
 #  endif
 #endif

+
+// Note: the nextpow2 functions have undefined behavior if 
+// x > 2^(n-1) for n of the 32 or 64 bit variants
+
 #if HAVE_BUILTIN_CLZ

 static inline uint32_t
@@ -39,7 +43,7 @@ static inline uint64_t
 uc_nextpow2_64(uint64_t x)
 {
    if (x <= 1) return 1;
-    return 1u << (64 - __builtin_clzll(x - 1));
+    return (uint64_t)1 << (64 - __builtin_clzll(x - 1));
    return x;
 }
 #else
@@ -61,7 +65,7 @@ uc_nextpow2(uint32_t x)
 }

 static inline uint64_t
-uc_nextpow2(uint64_t x)
+uc_nextpow2_64(uint64_t x)
 {
    if (x == 0) {
        return 1;