alloc-inl.h/ck_maybe_grow(): restore original exponential allocs

1 files changed, 23 insertions, 6 deletions

diff --git a/include/alloc-inl.h b/include/alloc-inl.h
index 11c1143a..b8c83db4 100644
--- a/include/alloc-inl.h
+++ b/include/alloc-inl.h
@@ -767,6 +767,20 @@ static inline void TRK_ck_free(void *ptr, const char *file, const char *func,
 
 #endif                                          /* _WANT_ORIGINAL_AFL_ALLOC */
 
+/* This function calculates the lowest power of 2 greater or equal its argument.
+ @return The rounded up power of 2 (if no overflow) or 0 on overflow.
+*/
+static inline size_t powerOf2Ceil(size_t in) {
+  if (in == 0 || in > (size_t)-1) return 0; /* avoid undefined behaviour under-/overflow */
+  size_t out = in - 1;
+  out |= out >> 1;
+  out |= out >> 2;
+  out |= out >> 4;
+  out |= out >> 8;
+  out |= out >> 16;
+  return out + 1;
+}
+
 /* This function makes sure *size is > size_needed after call.
  It will realloc *buf otherwise.
  *size will grow exponentially as per:
@@ -784,16 +798,19 @@ static inline void *ck_maybe_grow(void **buf, size_t *size,
   if (likely(*size >= size_needed)) return *buf;
 
   /* No initial size was set */
-  if (*size == 0) *size = INITIAL_GROWTH_SIZE;
-  while (*size < size_needed) {
+  if (size_needed < INITIAL_GROWTH_SIZE) size_needed = INITIAL_GROWTH_SIZE;
 
-    /* in case of overflow we'll realloc to size_needed */
-    if (2*(*size) < size_needed) *size = size_needed;
-    else *size *= 2;
+  /* grow exponentially */
+  size_t next_size = powerOf2Ceil(size_needed);
 
+  /* handle overflow */
+  if (!next_size) {
+    next_size = size_needed;
   }
 
-  *buf = ck_realloc(*buf, *size);
+  /* alloc */
+  *buf = ck_realloc(*buf, next_size);
+  *size = next_size;
 
   return *buf;