Eliminate ATTRIB() use

.gitignore

@@ -2,3 +2,4 @@
 .Rhistory
 .RData
 docs
+compile_commands.json

src/inspect.cpp

@@ -47,8 +47,9 @@ class GrowableList {
   }
 };
 
-SEXP obj_children_(SEXP x, std::map<SEXP, int>& seen, double max_depth, Expand expand);
+SEXP collect_attribs(SEXP x);
 bool is_namespace(cpp11::environment env);
+SEXP obj_children_(SEXP x, std::map<SEXP, int>& seen, double max_depth, Expand expand);
 
 bool is_altrep(SEXP x) {
 #if defined(R_VERSION) && R_VERSION >= R_Version(3, 5, 0)
@@ -320,9 +321,10 @@ SEXP obj_children_(
     }
   }
 
-  // CHARSXPs have fake attriibutes
-  if (max_depth > 0 && TYPEOF(x) != CHARSXP && !Rf_isNull(ATTRIB(x))) {
-    recurse(&children, seen, "_attrib", ATTRIB(x), max_depth, expand);
+  // CHARSXPs have fake attributes so don't inspecct them
+  if (max_depth > 0 && TYPEOF(x) != CHARSXP && ANY_ATTRIB(x)) {
+    recurse(&children, seen, "_attrib", PROTECT(collect_attribs(x)), max_depth, expand);
+    UNPROTECT(1);
   }
 
   SEXP out = PROTECT(children.vector());
@@ -335,6 +337,26 @@ SEXP obj_children_(
   return out;
 }
 
+// Collect attributes into a pairlist
+SEXP collect_attribs(SEXP x) {
+  SEXP sentinel = PROTECT(Rf_cons(R_NilValue, R_NilValue));
+  SEXP tail = sentinel;
+
+  R_mapAttrib(x, [](SEXP tag, SEXP val, void* data) -> SEXP {
+    SEXP* tail = (SEXP*)data;
+
+    SEXP node = Rf_cons(val, R_NilValue);
+    SETCDR(*tail, node);
+    SET_TAG(node, tag);
+
+    *tail = node;
+    return NULL;
+  }, &tail);
+
+  UNPROTECT(1);
+  return CDR(sentinel);
+}
+
 
 [[cpp11::register]]
 cpp11::list obj_inspect_(SEXP x,

src/size.cpp

@@ -83,8 +83,15 @@ double obj_size_tree(SEXP x,
 #endif
 
   // CHARSXPs have fake attributes
-  if (TYPEOF(x) != CHARSXP )
-    size += obj_size_tree(ATTRIB(x), base_env, sizeof_node, sizeof_vector, seen, depth + 1);
+  if (TYPEOF(x) != CHARSXP && ANY_ATTRIB(x)) {
+    SEXP attribs = PROTECT(collect_attribs(x));
+    for (SEXP node = attribs; node != R_NilValue; node = CDR(node)) {
+      size += sizeof_node;
+      size += obj_size_tree(TAG(node), base_env, sizeof_node, sizeof_vector, seen, depth + 1);
+      size += obj_size_tree(CAR(node), base_env, sizeof_node, sizeof_vector, seen, depth + 1);
+    }
+    UNPROTECT(1);
+  }
 
   switch (TYPEOF(x)) {
   // Vectors -------------------------------------------------------------------

src/utils.h

@@ -39,4 +39,37 @@ static inline
 SEXP R_ParentEnv(SEXP x) {
   return ENCLOS(x);
 }
+
+static inline
+int ANY_ATTRIB(SEXP x) {
+  return ATTRIB(x) != R_NilValue;
+}
+#endif
+
+#if R_VERSION < R_Version(4, 6, 0)
+// Polyfill for R_mapAttrib(), available in R >= 4.6.0.
+// Pulled exactly as-is from R:
+// https://github.com/r-devel/r-svn/blob/a39f4a28848fd02a1310b455353a871f2bb1965b/src/main/attrib.c#L2014
+// https://github.com/r-devel/r-svn/blob/a39f4a28848fd02a1310b455353a871f2bb1965b/doc/manual/R-exts.texi#L17920
+static inline
+SEXP R_mapAttrib(SEXP x, SEXP (*FUN)(SEXP, SEXP, void *), void *data) {
+  PROTECT_INDEX api;
+  SEXP a = ATTRIB(x);
+  SEXP val = NULL;
+
+  PROTECT_WITH_INDEX(a, &api);
+  while (a != R_NilValue) {
+    SEXP tag = PROTECT(TAG(a));
+    SEXP attr = PROTECT(CAR(a));
+    val = FUN(tag, attr, data);
+    UNPROTECT(2);
+    if (val != NULL)
+      break;
+    REPROTECT(a = CDR(a), api);
+  }
+  UNPROTECT(1);
+  return val;
+}
 #endif
+
+SEXP collect_attribs(SEXP x);