Issue #1307 - Part 4: Stop using variable-length arrays.

"USING VLA'S IS ACTIVELY STUPID! It generates much more code, and much
slower code (and more fragile code), than just using a fixed key size
would have done." -- Linus Torvalds

2 files changed, 20 insertions, 38 deletions

diff --git a/memory/mozjemalloc/jemalloc.c b/memory/mozjemalloc/jemalloc.c
index ccbc1aeba..c46e3c047 100644
--- a/memory/mozjemalloc/jemalloc.c
+++ b/memory/mozjemalloc/jemalloc.c
@@ -378,10 +378,6 @@ void *_mmap(void *addr, size_t length, int prot, int flags,
 #define __DECONST(type, var) ((type)(uintptr_t)(const void *)(var))
 #endif
 
-#ifdef MOZ_MEMORY_WINDOWS
-   /* MSVC++ does not support C99 variable-length arrays. */
-#  define RB_NO_C99_VARARRAYS
-#endif
 #include "rb.h"
 
 #ifdef MALLOC_DEBUG
diff --git a/memory/mozjemalloc/rb.h b/memory/mozjemalloc/rb.h
index 431ad9ddb..a1b08973b 100644
--- a/memory/mozjemalloc/rb.h
+++ b/memory/mozjemalloc/rb.h
@@ -36,7 +36,6 @@
  *   (Optional.)
  *   #define SIZEOF_PTR ...
  *   #define SIZEOF_PTR_2POW ...
- *   #define RB_NO_C99_VARARRAYS
  *
  *   (Optional, see assert(3).)
  *   #define NDEBUG
@@ -769,39 +768,26 @@ a_prefix##remove(a_tree_type *tree, a_type *node) {			\
  * effort.
  */
 
-#ifdef RB_NO_C99_VARARRAYS
-   /*
-    * Avoid using variable-length arrays, at the cost of using more stack space.
-    * Size the path arrays such that they are always large enough, even if a
-    * tree consumes all of memory.  Since each node must contain a minimum of
-    * two pointers, there can never be more nodes than:
-    *
-    *   1 << ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1))
-    *
-    * Since the depth of a tree is limited to 3*lg(#nodes), the maximum depth
-    * is:
-    *
-    *   (3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
-    *
-    * This works out to a maximum depth of 87 and 180 for 32- and 64-bit
-    * systems, respectively (approximatly 348 and 1440 bytes, respectively).
-    */
-#  define rbp_compute_f_height(a_type, a_field, a_tree)
-#  define rbp_f_height	(3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
-#  define rbp_compute_fr_height(a_type, a_field, a_tree)
-#  define rbp_fr_height	(3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
-#else
-#  define rbp_compute_f_height(a_type, a_field, a_tree)			\
-    /* Compute the maximum possible tree depth (3X the black height). */\
-    unsigned rbp_f_height;						\
-    rbp_black_height(a_type, a_field, a_tree, rbp_f_height);		\
-    rbp_f_height *= 3;
-#  define rbp_compute_fr_height(a_type, a_field, a_tree)		\
-    /* Compute the maximum possible tree depth (3X the black height). */\
-    unsigned rbp_fr_height;						\
-    rbp_black_height(a_type, a_field, a_tree, rbp_fr_height);		\
-    rbp_fr_height *= 3;
-#endif
+/*
+ * Avoid using variable-length arrays.
+ * Size the path arrays such that they are always large enough, even if a
+ * tree consumes all of memory. Since each node must contain a minimum of
+ * two pointers, there can never be more nodes than:
+ *
+ *   1 << ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1))
+ *
+ * Since the depth of a tree is limited to 3*lg(#nodes), the maximum depth
+ * is:
+ *
+ *   (3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
+ *
+ * This works out to a maximum depth of 87 and 180 for 32- and 64-bit
+ * systems, respectively (approximatly 348 and 1440 bytes, respectively).
+ */
+#define rbp_compute_f_height(a_type, a_field, a_tree)
+#define rbp_f_height	(3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
+#define rbp_compute_fr_height(a_type, a_field, a_tree)
+#define rbp_fr_height	(3 * ((SIZEOF_PTR<<3) - (SIZEOF_PTR_2POW+1)))
 
 #define	rb_foreach_begin(a_type, a_field, a_tree, a_var) {		\
     rbp_compute_f_height(a_type, a_field, a_tree)			\