diff --git a/lfs.c b/lfs.c
index 3c233d63..155ea19a 100644
--- a/lfs.c
+++ b/lfs.c
@@ -3900,8 +3900,9 @@ static lfs_scmp_t lfsr_rbyd_namelookup(lfs_t *lfs, const lfsr_rbyd_t *rbyd,
 
 /// B-tree operations ///
 
-// convenience operations
+#define LFSR_BTREE_NULL() ((lfsr_btree_t){.weight=0, .trunk=0})
 
+// convenience operations
 static inline int lfsr_btree_cmp(
         const lfsr_btree_t *a,
         const lfsr_btree_t *b) {
@@ -4036,14 +4037,6 @@ static int lfsr_data_readbtree(lfs_t *lfs, lfsr_data_t *data,
 
 // core btree operations
 
-static int lfsr_btree_alloc(lfs_t *lfs, lfsr_btree_t *btree) {
-    (void)lfs;
-    // TODO do we need this function then?
-    // allocate lazily
-    *btree = (lfsr_btree_t){.trunk=0, .weight=0};
-    return 0;
-}
-
 static int lfsr_btree_lookupnext_(lfs_t *lfs, const lfsr_btree_t *btree,
         lfsr_bid_t bid,
         lfsr_bid_t *bid_, lfsr_rbyd_t *rbyd_, lfsr_srid_t *rid_,
@@ -5204,6 +5197,14 @@ static int lfsr_sprout_compact(lfs_t *lfs, const lfsr_rbyd_t *rbyd_,
 
 // shrub things
 
+#define LFSR_SHRUB_NULL(_block) \
+    ((lfsr_shrub_t){ \
+        .weight=0, \
+        .blocks[0]=_block, \
+        .trunk=LFSR_RBYD_ISSHRUB | 0, \
+        /* force estimate recalculation */ \
+        .estimate=-1})
+
 // helper functions
 static inline bool lfsr_shrub_isshrub(const lfsr_shrub_t *shrub) {
     return lfsr_rbyd_isshrub((const lfsr_rbyd_t*)shrub);
@@ -6886,10 +6887,7 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
 
         // new mtree?
         if (lfsr_mtree_ismptr(&lfs->mtree)) {
-            err = lfsr_btree_alloc(lfs, &mtree_.u.btree);
-            if (err) {
-                goto failed;
-            }
+            mtree_.u.btree = LFSR_BTREE_NULL();
 
             uint8_t mdir_buf[2*LFSR_MPTR_DSIZE];
             err = lfsr_btree_commit(lfs, &mtree_.u.btree,
@@ -10553,11 +10551,7 @@ static int lfsr_file_carve(lfs_t *lfs, lfsr_file_t *file,
                     LFSR_DATA_BPTR_(&file->bshrub.u.bptr, left.buf));
         }
 
-        file->bshrub.u.bshrub.blocks[0] = file->o.mdir.rbyd.blocks[0];
-        file->bshrub.u.bshrub.trunk = LFSR_RBYD_ISSHRUB | 0;
-        file->bshrub.u.bshrub.weight = 0;
-        // force estimate recalculation
-        file->bshrub.u.bshrub.estimate = -1;
+        file->bshrub.u.bshrub = LFSR_SHRUB_NULL(file->o.mdir.rbyd.blocks[0]);
 
         if (attr_count > 0) {
             LFS_ASSERT(attr_count <= sizeof(attrs)/sizeof(lfsr_attr_t));
diff --git a/tests/test_badblocks.toml b/tests/test_badblocks.toml
index 8744c3fa..40c1f6cb 100644
--- a/tests/test_badblocks.toml
+++ b/tests/test_badblocks.toml
@@ -42,8 +42,7 @@ code = '''
         lfs_alloc_ckpoint(&lfs);
 
         // create a btree
-        lfsr_btree_t btree;
-        lfsr_btree_alloc(&lfs, &btree) => 0;
+        lfsr_btree_t btree = LFSR_BTREE_NULL();
 
         // set up a simulation to compare against
         char *sim = malloc(N);
@@ -150,8 +149,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     char *sim = malloc(N);
@@ -254,8 +252,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     char *sim = malloc(N);
diff --git a/tests/test_btree.toml b/tests/test_btree.toml
index c8a6343f..68df1d59 100644
--- a/tests/test_btree.toml
+++ b/tests/test_btree.toml
@@ -20,8 +20,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create an empty tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     printf("btree: w%d 0x%x.%x\n",
             btree.weight,
             btree.blocks[0],
@@ -52,8 +51,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     printf("btree: w%d 0x%x.%x\n",
@@ -94,8 +92,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -144,8 +141,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("b", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
@@ -195,8 +191,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -254,8 +249,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("c", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
@@ -316,8 +310,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfs_size_t n = 0;
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
@@ -367,8 +360,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfs_size_t n = 0;
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
@@ -419,8 +411,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //
@@ -502,8 +493,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfs_size_t n = 0;
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i*W, LFSR_ATTRS(
@@ -570,8 +560,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //
@@ -706,8 +695,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     // update the tree
@@ -752,8 +740,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -811,8 +798,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -884,8 +870,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -941,8 +926,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1028,8 +1012,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i*W, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1101,8 +1084,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i*W, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1245,8 +1227,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     // pop!
@@ -1302,8 +1283,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -1375,8 +1355,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -1448,8 +1427,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("a", 1)))) => 0;
     lfsr_btree_commit(&lfs, &btree, 1, LFSR_ATTRS(
@@ -1540,8 +1518,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1620,8 +1597,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1702,8 +1678,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1791,8 +1766,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i*W, LFSR_ATTRS(
                 LFSR_ATTR(
@@ -1897,8 +1871,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //
@@ -2048,8 +2021,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(
                 LFSR_TAG_DATA, +1,
@@ -2107,8 +2079,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +1, LFSR_DATA_BUF("_", 1)))) => 0;
 
@@ -2197,8 +2168,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(
                 LFSR_TAG_DATA, +W,
@@ -2257,8 +2227,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR(LFSR_TAG_DATA, +W, LFSR_DATA_BUF("_", 1)))) => 0;
 
@@ -2434,8 +2403,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // force it to split
 
@@ -2502,8 +2470,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // force it to split
 
@@ -2573,8 +2540,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // force it to split
 
@@ -2637,8 +2603,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // force it to split
 
@@ -2717,8 +2682,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //
@@ -2823,8 +2787,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //
@@ -2990,8 +2953,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a zero-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     printf("btree: w%d 0x%x.%x\n",
             btree.weight,
             btree.blocks[0],
@@ -3024,8 +2986,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a single-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3077,8 +3038,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3144,8 +3104,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3225,8 +3184,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a two-entry tree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3307,8 +3265,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     char name[3] = {
         'a'+((0/26/26) % 26), 'a'+((0/26) % 26), 'a'+(0 % 26)
     };
@@ -3380,8 +3337,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3495,8 +3451,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     char name[3] = {
         'a'+((0/26/26) % 26), 'a'+((0/26) % 26), 'a'+(0 % 26)
     };
@@ -3569,8 +3524,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +W,
@@ -3725,8 +3679,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +1,
@@ -3882,8 +3835,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfsr_btree_commit(&lfs, &btree, 0, LFSR_ATTRS(
             LFSR_ATTR_NAME(
                 LFSR_TAG_NAME, +W,
@@ -4088,8 +4040,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a tree with N elements
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
     lfs_size_t n = 0;
     for (lfs_size_t i = 0; i < N; i++) {
         lfsr_btree_commit(&lfs, &btree, i, LFSR_ATTRS(
@@ -4210,8 +4161,7 @@ code = '''
     lfs_alloc_ckpoint(&lfs);
 
     // create a btree
-    lfsr_btree_t btree;
-    lfsr_btree_alloc(&lfs, &btree) => 0;
+    lfsr_btree_t btree = LFSR_BTREE_NULL();
 
     // set up a simulation to compare against
     //