Dump largest refc binaries on oom crashes

Signed-off-by: Paul Guyot <[email protected]>

Author: pguyot

src/libAtomVM/context.c

@@ -1297,7 +1297,7 @@ COLD_FUNC void context_dump(Context *ctx)
         fprintf(stderr, "process_count = %zu\n", process_count);
         fprintf(stderr, "ports_count = %zu\n", ports_count);
         fprintf(stderr, "atoms_count = %zu\n", atom_table_count(glb->atom_table));
-        fprintf(stderr, "refc_binary_total_size = %zu\n", refc_binary_total_size(ctx));
+        refc_binary_dump_info(ctx);
     }
     fprintf(stderr, "\n\n**End Of Crash Report**\n");
 }

src/libAtomVM/refc_binary.c

@@ -141,3 +141,86 @@ size_t refc_binary_total_size(Context *ctx)
     synclist_unlock(&ctx->global->refc_binaries);
     return size;
 }
+
+COLD_FUNC void refc_binary_dump_info(Context *ctx)
+{
+    struct ListHead *item;
+    struct ListHead *refc_binaries = synclist_rdlock(&ctx->global->refc_binaries);
+
+    // Note: This only counts non-const refc binaries (ones that allocate memory).
+    // Const binaries (created by term_from_const_binary) point to existing data
+    // and are never added to the global refc_binaries list, so they don't appear here.
+
+    // First pass: count and calculate total size
+    size_t count = 0;
+    size_t total_size = 0;
+    LIST_FOR_EACH (item, refc_binaries) {
+        struct RefcBinary *refc = GET_LIST_ENTRY(item, struct RefcBinary, head);
+        count++;
+        total_size += refc->size;
+    }
+
+    fprintf(stderr, "refc_binary_count = %d\n", (int) count);
+    fprintf(stderr, "refc_binary_total_size = %d\n", (int) total_size);
+
+    if (count == 0) {
+        synclist_unlock(&ctx->global->refc_binaries);
+        return;
+    }
+
+// Find top 5 largest binaries
+#define TOP_N 5
+    struct RefcBinary *top[TOP_N] = { NULL };
+    size_t top_indices[TOP_N] = { 0 };
+
+    size_t index = 0;
+    LIST_FOR_EACH (item, refc_binaries) {
+        struct RefcBinary *refc = GET_LIST_ENTRY(item, struct RefcBinary, head);
+
+        // Try to insert into top 5
+        for (size_t i = 0; i < TOP_N; i++) {
+            if (top[i] == NULL || refc->size > top[i]->size) {
+                // Shift down
+                for (size_t j = TOP_N - 1; j > i; j--) {
+                    top[j] = top[j - 1];
+                    top_indices[j] = top_indices[j - 1];
+                }
+                top[i] = refc;
+                top_indices[i] = index;
+                break;
+            }
+        }
+        index++;
+    }
+
+    // Display top binaries
+    fprintf(stderr, "\nTop %d largest refc binaries:\n", TOP_N);
+    for (size_t i = 0; i < TOP_N && top[i] != NULL; i++) {
+        struct RefcBinary *refc = top[i];
+        fprintf(stderr, "  [%zu] size=%d bytes (%.1f%%), refcount=%d",
+            top_indices[i],
+            (int) refc->size,
+            (double) refc->size * 100.0 / (double) total_size,
+            (int) refc->ref_count);
+
+        if (refc->resource_type) {
+            fprintf(stderr, " [resource]");
+        }
+
+        // Print first 32 bytes as hex
+        fprintf(stderr, "\n      data: ");
+        size_t print_size = refc->size < 32 ? refc->size : 32;
+        for (size_t j = 0; j < print_size; j++) {
+            fprintf(stderr, "%02x", refc->data[j]);
+            if (j % 4 == 3 && j < print_size - 1) {
+                fprintf(stderr, " ");
+            }
+        }
+        if (refc->size > 32) {
+            fprintf(stderr, "...");
+        }
+        fprintf(stderr, "\n");
+    }
+
+    synclist_unlock(&ctx->global->refc_binaries);
+}

src/libAtomVM/refc_binary.h

@@ -142,6 +142,16 @@ term refc_binary_create_binary_info(Context *ctx);
  */
 size_t refc_binary_total_size(Context *ctx);
 
+/**
+ * @brief Dump detailed information about reference counted binaries
+ *
+ * @details This function prints diagnostic information including the count,
+ * total size, and details about the top 5 largest binaries including
+ * their first bytes. Used for debugging memory issues.
+ * @param ctx the context
+ */
+COLD_FUNC void refc_binary_dump_info(Context *ctx);
+
 #ifdef __cplusplus
 }
 #endif