atomvm · mfurga · Mar 20, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Added `erlang:node/1` BIF
 - Added `erts_internal:cmp_term/2`
+- Added support for `process_info/1` and `process_info/2` with list argument
 
 ### Changed
 

diff --git a/doc/src/apidocs/libatomvm/data_structures.rst b/doc/src/apidocs/libatomvm/data_structures.rst
@@ -23,7 +23,7 @@ Data Structures
    :allow-dot-graphs:
 .. doxygenstruct:: AVMPackData
    :allow-dot-graphs:
-.. doxygenstruct:: BuiltInAtomRequestSignal
+.. doxygenstruct:: ProcessInfoRequestSignal
    :allow-dot-graphs:
 .. doxygenstruct:: BuiltInAtomSignal
    :allow-dot-graphs:

diff --git a/src/libAtomVM/context.c b/src/libAtomVM/context.c
@@ -156,8 +156,8 @@ void context_destroy(Context *ctx)
     while (signal_message) {
         switch (signal_message->type) {
             case ProcessInfoRequestSignal: {
-                struct BuiltInAtomRequestSignal *request_signal
-                    = CONTAINER_OF(signal_message, struct BuiltInAtomRequestSignal, base);
+                struct ProcessInfoRequestSignal *request_signal
+                    = CONTAINER_OF(signal_message, struct ProcessInfoRequestSignal, base);
                 context_process_process_info_request_signal(ctx, request_signal, true);
                 break;
             }
@@ -312,36 +312,93 @@ void context_process_kill_signal(Context *ctx, struct TermSignal *signal)
     context_update_flags(ctx, ~NoFlags, Killed);
 }
 
-void context_process_process_info_request_signal(Context *ctx, struct BuiltInAtomRequestSignal *signal, bool process_table_locked)
+void context_process_process_info_request_signal(Context *ctx, struct ProcessInfoRequestSignal *signal, bool process_table_locked)
 {
     Context *target;
     if (process_table_locked) {
         target = globalcontext_get_process_nolock(ctx->global, signal->sender_pid);
     } else {
         target = globalcontext_get_process_lock(ctx->global, signal->sender_pid);
     }
-    if (LIKELY(target)) {
+
+    if (UNLIKELY(!target)) {
+        return;
+    }
+
+    if (signal->mode == PROCESS_INFO_SINGLE) {
+        term atom = signal->atoms[0];
         size_t term_size;
-        if (context_get_process_info(ctx, NULL, &term_size, signal->atom, NULL)) {
-            Heap heap;
-            if (UNLIKELY(memory_init_heap(&heap, term_size) != MEMORY_GC_OK)) {
-                mailbox_send_immediate_signal(target, TrapExceptionSignal, OUT_OF_MEMORY_ATOM);
-            } else {
-                term ret;
-                if (context_get_process_info(ctx, &ret, NULL, signal->atom, &heap)) {
-                    mailbox_send_term_signal(target, TrapAnswerSignal, ret);
-                } else {
-                    mailbox_send_immediate_signal(target, TrapExceptionSignal, ret);
-                }
-                memory_destroy_heap(&heap, ctx->global);
+        if (!context_get_process_info(ctx, NULL, &term_size, atom, NULL)) {
+            mailbox_send_immediate_signal(target, TrapExceptionSignal, BADARG_ATOM);
+            goto done;
+        }
+
+        Heap heap;
+        if (UNLIKELY(memory_init_heap(&heap, term_size) != MEMORY_GC_OK)) {
+            mailbox_send_immediate_signal(target, TrapExceptionSignal, OUT_OF_MEMORY_ATOM);
+            goto done;
+        }
+
+        term ret;
+        if (context_get_process_info(ctx, &ret, NULL, atom, &heap)) {
+            // return [] when unregistered (BEAM backward compatibility)
+            if (atom == REGISTERED_NAME_ATOM && term_is_tuple(ret) && term_is_nil(term_get_tuple_element(ret, 1))) {
+                ret = term_nil();
             }
+            mailbox_send_term_signal(target, TrapAnswerSignal, ret);
         } else {
-            mailbox_send_immediate_signal(target, TrapExceptionSignal, BADARG_ATOM);
+            mailbox_send_immediate_signal(target, TrapExceptionSignal, ret);
+        }
+        memory_destroy_heap(&heap, ctx->global);
+    } else {
+        size_t total_size = 0;
+        for (size_t i = 0; i < signal->len; i++) {
+            size_t item_size;
+            if (UNLIKELY(!context_get_process_info(ctx, NULL, &item_size, signal->atoms[i], NULL))) {
+                mailbox_send_immediate_signal(target, TrapExceptionSignal, BADARG_ATOM);
+                goto done;
+            }
+            total_size += item_size + CONS_SIZE;
+        }
+
+        if (signal->len == 0) {
+            mailbox_send_term_signal(target, TrapAnswerSignal, term_nil());
+            goto done;
         }
-        if (!process_table_locked) {
-            globalcontext_get_process_unlock(ctx->global, target);
+
+        Heap heap;
+        if (UNLIKELY(memory_init_heap(&heap, total_size) != MEMORY_GC_OK)) {
+            mailbox_send_immediate_signal(target, TrapExceptionSignal, OUT_OF_MEMORY_ATOM);
+            goto done;
+        }
+
+        // Build list backwards to preserve input order
+        term result = term_nil();
+        bool build_ok = true;
+        for (ssize_t i = (ssize_t) signal->len - 1; i >= 0; i--) {
+            term item_result;
+            if (UNLIKELY(!context_get_process_info(ctx, &item_result, NULL, signal->atoms[i], &heap))) {
+                mailbox_send_immediate_signal(target, TrapExceptionSignal, item_result);
+                build_ok = false;
+                break;
+            }
+
+            if (signal->mode == PROCESS_INFO_LIST_OMIT_UNREGISTERED && signal->atoms[i] == REGISTERED_NAME_ATOM && term_is_nil(term_get_tuple_element(item_result, 1))) {
+                continue;
+            }
+
+            result = term_list_prepend(item_result, result, &heap);
         }
-    } // else: sender died
+        if (LIKELY(build_ok)) {
+            mailbox_send_term_signal(target, TrapAnswerSignal, result);
+        }
+        memory_destroy_heap(&heap, ctx->global);
+    }
+
+done:
+    if (!process_table_locked) {
+        globalcontext_get_process_unlock(ctx->global, target);
+    }
 }
 
 bool context_process_signal_trap_answer(Context *ctx, struct TermSignal *signal)
@@ -525,6 +582,7 @@ bool context_get_process_info(Context *ctx, term *out, size_t *term_size, term a
         case MESSAGE_QUEUE_LEN_ATOM:
         case REGISTERED_NAME_ATOM:
         case MEMORY_ATOM:
+        case TRAP_EXIT_ATOM:
             ret_size = TUPLE_SIZE(2);
             break;
         case LINKS_ATOM: {
@@ -589,12 +647,8 @@ bool context_get_process_info(Context *ctx, term *out, size_t *term_size, term a
         // registered_name for process or port..
         case REGISTERED_NAME_ATOM: {
             term name = globalcontext_get_registered_name_process(ctx->global, ctx->process_id);
-            if (term_is_invalid_term((name))) {
-                ret = term_nil(); // Set ret to an empty list to match erlang behaviour
-            } else {
-                term_put_tuple_element(ret, 0, REGISTERED_NAME_ATOM);
-                term_put_tuple_element(ret, 1, name);
-            }
+            term_put_tuple_element(ret, 0, REGISTERED_NAME_ATOM);
+            term_put_tuple_element(ret, 1, term_is_invalid_term(name) ? term_nil() : name);
             break;
         }
 
@@ -630,6 +684,13 @@ bool context_get_process_info(Context *ctx, term *out, size_t *term_size, term a
             break;
         }
 
+        // true if a process traps exits, otherwise false
+        case TRAP_EXIT_ATOM: {
+            term_put_tuple_element(ret, 0, TRAP_EXIT_ATOM);
+            term_put_tuple_element(ret, 1, ctx->trap_exit ? TRUE_ATOM : FALSE_ATOM);
+            break;
+        }
+
         // pids of linked processes
         case LINKS_ATOM: {
             term_put_tuple_element(ret, 0, LINKS_ATOM);

diff --git a/src/libAtomVM/context.h b/src/libAtomVM/context.h
@@ -430,10 +430,10 @@ void context_process_kill_signal(Context *ctx, struct TermSignal *signal);
  * @brief Process a process info request signal.
  *
  * @param ctx the context being executed
- * @param signal the process info signal
+ * @param signal the process info request signal
  * @param process_table_locked whether process table is already locked
  */
-void context_process_process_info_request_signal(Context *ctx, struct BuiltInAtomRequestSignal *signal, bool process_table_locked);
+void context_process_process_info_request_signal(Context *ctx, struct ProcessInfoRequestSignal *signal, bool process_table_locked);
 
 /**
  * @brief Process a trap answer signal.

diff --git a/src/libAtomVM/jit.c b/src/libAtomVM/jit.c
@@ -897,8 +897,8 @@ static Context *jit_process_signal_messages(Context *ctx, JITState *jit_state)
                 break;
             }
             case ProcessInfoRequestSignal: {
-                struct BuiltInAtomRequestSignal *request_signal
-                    = CONTAINER_OF(signal_message, struct BuiltInAtomRequestSignal, base);
+                struct ProcessInfoRequestSignal *request_signal
+                    = CONTAINER_OF(signal_message, struct ProcessInfoRequestSignal, base);
                 context_process_process_info_request_signal(ctx, request_signal, false);
                 break;
             }

diff --git a/src/libAtomVM/mailbox.c b/src/libAtomVM/mailbox.c
@@ -110,8 +110,8 @@
             break;
         }
         case ProcessInfoRequestSignal: {
-            struct BuiltInAtomRequestSignal *request_signal
-                = CONTAINER_OF(m, struct BuiltInAtomRequestSignal, base);
+            struct ProcessInfoRequestSignal *request_signal
+                = CONTAINER_OF(m, struct ProcessInfoRequestSignal, base);
             free(request_signal);
             break;
         }
@@ -217,7 +217,7 @@
    MailboxMessage *current_first = NULL;
    do {
        m->next = current_first;
    } while (!ATOMIC_COMPARE_EXCHANGE_WEAK_PTR(&c->mailbox.outer_first, &current_first, m));
 }

 void mailbox_post_message(Context *c, MailboxMessage *m)
@@ -291,19 +291,24 @@
     mailbox_post_message(c, &immediate_signal->base);
 }
 
-void mailbox_send_built_in_atom_request_signal(
-    Context *c, enum MessageType type, int32_t pid, term atom)
+void mailbox_send_process_info_request_signal(
+    Context *c, int32_t sender_pid, process_info_mode_t mode, const term *atoms, size_t len)
 {
-    struct BuiltInAtomRequestSignal *atom_request = malloc(sizeof(struct BuiltInAtomRequestSignal));
-    if (IS_NULL_PTR(atom_request)) {
+    struct ProcessInfoRequestSignal *signal = malloc(
+        sizeof(struct ProcessInfoRequestSignal) + len * sizeof(term));
+    if (IS_NULL_PTR(signal)) {
         fprintf(stderr, "Failed to allocate memory: %s:%i.\n", __FILE__, __LINE__);
         return;
     }
-    atom_request->base.type = type;
-    atom_request->sender_pid = pid;
-    atom_request->atom = atom;
+    signal->base.type = ProcessInfoRequestSignal;
+    signal->sender_pid = sender_pid;
+    signal->mode = mode;
+    signal->len = len;
+    for (size_t i = 0; i < len; i++) {
+        signal->atoms[i] = atoms[i];
+    }
 
-    mailbox_post_message(c, &atom_request->base);
+    mailbox_post_message(c, &signal->base);
 }
 
 void mailbox_send_ref_signal(Context *c, enum MessageType type, uint64_t ref_ticks)

diff --git a/src/libAtomVM/mailbox.h b/src/libAtomVM/mailbox.h
@@ -137,12 +137,21 @@ struct ImmediateSignal
     term immediate;
 };
 
-struct BuiltInAtomRequestSignal
+typedef enum
+{
+    PROCESS_INFO_SINGLE,
+    PROCESS_INFO_LIST,
+    PROCESS_INFO_LIST_OMIT_UNREGISTERED,
+} process_info_mode_t;
+
+struct ProcessInfoRequestSignal
 {
     MailboxMessage base;
 
     int32_t sender_pid;
-    term atom;
+    process_info_mode_t mode;
+    size_t len;
+    term atoms[];
 };
 
 struct RefSignal
@@ -248,15 +257,16 @@ void mailbox_send_term_signal(Context *c, enum MessageType type, term t);
 void mailbox_send_immediate_signal(Context *c, enum MessageType type, term immediate);
 
 /**
- * @brief Sends a built-in atom-based request signal to a certain mailbox.
+ * @brief Sends a process info request signal to a certain mailbox.
  *
  * @param c the process context.
- * @param type the type of the signal
  * @param sender_pid the sender of the signal (to get the answer)
- * @param atom the built-in atom
+ * @param mode controls result shape and registered_name handling
+ * @param atoms array of atom terms to query
+ * @param len number of atoms in the array
  */
-void mailbox_send_built_in_atom_request_signal(
-    Context *c, enum MessageType type, int32_t sender_pid, term atom);
+void mailbox_send_process_info_request_signal(
+    Context *c, int32_t sender_pid, process_info_mode_t mode, const term *atoms, size_t len);
 
 /**
  * @brief Sends a ref signal to a certain mailbox.