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diff --git a/deps/jemalloc/include/jemalloc/internal/hook.h b/deps/jemalloc/include/jemalloc/internal/hook.h
new file mode 100644
index 0000000..ee246b1
--- /dev/null
+++ b/deps/jemalloc/include/jemalloc/internal/hook.h
@@ -0,0 +1,163 @@
+#ifndef JEMALLOC_INTERNAL_HOOK_H
+#define JEMALLOC_INTERNAL_HOOK_H
+
+#include "jemalloc/internal/tsd.h"
+
+/*
+ * This API is *extremely* experimental, and may get ripped out, changed in API-
+ * and ABI-incompatible ways, be insufficiently or incorrectly documented, etc.
+ *
+ * It allows hooking the stateful parts of the API to see changes as they
+ * happen.
+ *
+ * Allocation hooks are called after the allocation is done, free hooks are
+ * called before the free is done, and expand hooks are called after the
+ * allocation is expanded.
+ *
+ * For realloc and rallocx, if the expansion happens in place, the expansion
+ * hook is called.  If it is moved, then the alloc hook is called on the new
+ * location, and then the free hook is called on the old location (i.e. both
+ * hooks are invoked in between the alloc and the dalloc).
+ *
+ * If we return NULL from OOM, then usize might not be trustworthy.  Calling
+ * realloc(NULL, size) only calls the alloc hook, and calling realloc(ptr, 0)
+ * only calls the free hook.  (Calling realloc(NULL, 0) is treated as malloc(0),
+ * and only calls the alloc hook).
+ *
+ * Reentrancy:
+ *   Reentrancy is guarded against from within the hook implementation.  If you
+ *   call allocator functions from within a hook, the hooks will not be invoked
+ *   again.
+ * Threading:
+ *   The installation of a hook synchronizes with all its uses.  If you can
+ *   prove the installation of a hook happens-before a jemalloc entry point,
+ *   then the hook will get invoked (unless there's a racing removal).
+ *
+ *   Hook insertion appears to be atomic at a per-thread level (i.e. if a thread
+ *   allocates and has the alloc hook invoked, then a subsequent free on the
+ *   same thread will also have the free hook invoked).
+ *
+ *   The *removal* of a hook does *not* block until all threads are done with
+ *   the hook.  Hook authors have to be resilient to this, and need some
+ *   out-of-band mechanism for cleaning up any dynamically allocated memory
+ *   associated with their hook.
+ * Ordering:
+ *   Order of hook execution is unspecified, and may be different than insertion
+ *   order.
+ */
+
+#define HOOK_MAX 4
+
+enum hook_alloc_e {
+	hook_alloc_malloc,
+	hook_alloc_posix_memalign,
+	hook_alloc_aligned_alloc,
+	hook_alloc_calloc,
+	hook_alloc_memalign,
+	hook_alloc_valloc,
+	hook_alloc_mallocx,
+
+	/* The reallocating functions have both alloc and dalloc variants */
+	hook_alloc_realloc,
+	hook_alloc_rallocx,
+};
+/*
+ * We put the enum typedef after the enum, since this file may get included by
+ * jemalloc_cpp.cpp, and C++ disallows enum forward declarations.
+ */
+typedef enum hook_alloc_e hook_alloc_t;
+
+enum hook_dalloc_e {
+	hook_dalloc_free,
+	hook_dalloc_dallocx,
+	hook_dalloc_sdallocx,
+
+	/*
+	 * The dalloc halves of reallocation (not called if in-place expansion
+	 * happens).
+	 */
+	hook_dalloc_realloc,
+	hook_dalloc_rallocx,
+};
+typedef enum hook_dalloc_e hook_dalloc_t;
+
+
+enum hook_expand_e {
+	hook_expand_realloc,
+	hook_expand_rallocx,
+	hook_expand_xallocx,
+};
+typedef enum hook_expand_e hook_expand_t;
+
+typedef void (*hook_alloc)(
+    void *extra, hook_alloc_t type, void *result, uintptr_t result_raw,
+    uintptr_t args_raw[3]);
+
+typedef void (*hook_dalloc)(
+    void *extra, hook_dalloc_t type, void *address, uintptr_t args_raw[3]);
+
+typedef void (*hook_expand)(
+    void *extra, hook_expand_t type, void *address, size_t old_usize,
+    size_t new_usize, uintptr_t result_raw, uintptr_t args_raw[4]);
+
+typedef struct hooks_s hooks_t;
+struct hooks_s {
+	hook_alloc alloc_hook;
+	hook_dalloc dalloc_hook;
+	hook_expand expand_hook;
+	void *extra;
+};
+
+/*
+ * Begin implementation details; everything above this point might one day live
+ * in a public API.  Everything below this point never will.
+ */
+
+/*
+ * The realloc pathways haven't gotten any refactoring love in a while, and it's
+ * fairly difficult to pass information from the entry point to the hooks.  We
+ * put the informaiton the hooks will need into a struct to encapsulate
+ * everything.
+ *
+ * Much of these pathways are force-inlined, so that the compiler can avoid
+ * materializing this struct until we hit an extern arena function.  For fairly
+ * goofy reasons, *many* of the realloc paths hit an extern arena function.
+ * These paths are cold enough that it doesn't matter; eventually, we should
+ * rewrite the realloc code to make the expand-in-place and the
+ * free-then-realloc paths more orthogonal, at which point we don't need to
+ * spread the hook logic all over the place.
+ */
+typedef struct hook_ralloc_args_s hook_ralloc_args_t;
+struct hook_ralloc_args_s {
+	/* I.e. as opposed to rallocx. */
+	bool is_realloc;
+	/*
+	 * The expand hook takes 4 arguments, even if only 3 are actually used;
+	 * we add an extra one in case the user decides to memcpy without
+	 * looking too closely at the hooked function.
+	 */
+	uintptr_t args[4];
+};
+
+/*
+ * Returns an opaque handle to be used when removing the hook.  NULL means that
+ * we couldn't install the hook.
+ */
+bool hook_boot();
+
+void *hook_install(tsdn_t *tsdn, hooks_t *hooks);
+/* Uninstalls the hook with the handle previously returned from hook_install. */
+void hook_remove(tsdn_t *tsdn, void *opaque);
+
+/* Hooks */
+
+void hook_invoke_alloc(hook_alloc_t type, void *result, uintptr_t result_raw,
+    uintptr_t args_raw[3]);
+
+void hook_invoke_dalloc(hook_dalloc_t type, void *address,
+    uintptr_t args_raw[3]);
+
+void hook_invoke_expand(hook_expand_t type, void *address, size_t old_usize,
+    size_t new_usize, uintptr_t result_raw, uintptr_t args_raw[4]);
+
+#endif /* JEMALLOC_INTERNAL_HOOK_H */