Fix unitialized var access on allocation failure

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        otp_version: [21,23,26,27,28]
+        otp_version: [21,23,26,27,28,29]
         os: [ubuntu-latest]
         rebar: [rebar, rebar3]
 
@@ -135,6 +135,10 @@ jobs:
           git config --global core.eol lf
     - uses: actions/checkout@v6
     - uses: erlef/setup-beam@v1
+      # New runner images report win25-vs2026 and
+      # setup-beam cannot map (yet), so override for now
+      env:
+        ImageOS: ${{ matrix.os == 'windows-2025' && 'win25' || 'win22' }}
       with:
         otp-version: '27'
         rebar3-version: '3.23'

c_src/decoder.c

@@ -49,8 +49,8 @@ typedef struct {
     int             st_top;
 } Decoder;
 
-// Returns an allocated resource or crashes the VM. No need to
-// check return pointer for NULL
+// Returns an allocated resource or NULL if the term stack
+// cannot be allocated
 static Decoder*
 dec_new(ErlNifEnv* env)
 {
@@ -60,23 +60,21 @@ dec_new(ErlNifEnv* env)
     assert(d != NULL);
     int i;
 
-    d->atoms = st;
+    // Zero everything and only set non-0 fields
+    memset(d, 0, sizeof(*d));
 
+    d->atoms = st;
     d->bytes_per_red = DEFAULT_BYTES_PER_REDUCTION;
-    d->is_partial = 0;
-    d->return_maps = 0;
-    d->return_trailer = 0;
-    d->dedupe_keys = 0;
-    d->copy_strings = 0;
     d->null_term = d->atoms->atom_null;
-
-    d->p = NULL;
     d->len = -1;
-    d->i = 0;
 
     d->st_data = (char*) enif_alloc(STACK_SIZE_INC);
+    if(d->st_data == NULL) {
+        enif_release_resource(d);
+        return NULL;
+    }
+
     d->st_size = STACK_SIZE_INC;
-    d->st_top = 0;
 
     for(i = 0; i < d->st_size; i++) {
         d->st_data[i] = st_invalid;
@@ -468,9 +466,11 @@ decode_init(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
         return enif_make_badarg(env);
     }
 
-    // If allocation fails VM will crash.
     d = dec_new(env);
-    assert(d != NULL);
+    if(d == NULL) {
+        return enif_make_tuple2(env, st->atom_error,
+                make_atom(env, "internal_error"));
+    }
 
     tmp_argv[0] = argv[0];
     tmp_argv[1] = enif_make_resource(env, d);

c_src/encoder.c

@@ -162,29 +162,21 @@ enc_new(ErlNifEnv* env)
     jiffy_st* st = (jiffy_st*) enif_priv_data(env);
     Encoder* e = enif_alloc_resource(st->res_enc, sizeof(Encoder));
 
+    // Zero everything so enc_destroy() never sees an uninitialized
+    // have_buffer if we bail out before the encoder is fully built
+    memset(e, 0, sizeof(*e));
+
     e->atoms = st;
     e->bytes_per_red = DEFAULT_BYTES_PER_REDUCTION;
-    e->uescape = 0;
-    e->pretty = 0;
-    e->use_nil = 0;
-    e->escape_forward_slashes = 0;
-    e->shiftcnt = 0;
-    e->count = 0;
-
-    e->iosize = 0;
     e->iolist = enif_make_list(env, 0);
 
-    e->partial_output = 0;
-
     if(!enif_alloc_binary(BIN_INC_SIZE, &e->buffer)) {
         enif_release_resource(e);
         return NULL;
     }
 
     e->have_buffer = 1;
-
     e->p = e->buffer.data;
-    e->i = 0;
 
     return e;
 }