Add comment on serialize/unserialize for resizable vectors.

luke · luke · commit 8e31e44bf444 · 2025-11-29T18:41:40.000Z
git-svn-id: https://svn.r-project.org/R/trunk@89076 00db46b3-68df-0310-9c12-caf00c1e9a41
diff --git a/src/main/memory.c b/src/main/memory.c
@@ -5010,6 +5010,10 @@ NORET R_len_t R_BadLongVector(SEXP x, const char *file, int line)
 
 /* Highly experimental resizable vector support */
 
+/* Serializing and unserializing preserves the GROWABLE bit, but
+   XTRUELENGTH is set to zero by unserialize. A vector with the
+   GROWABLE bit set but XTRUELENGTH zero is therefore considered not
+   resizeble. */ 
 bool R_isResizable(SEXP x)
 {
     return isVector(x) && ! ALTREP(x) && GROWABLE_BIT_SET(x) &&

Original file line number	Diff line number	Diff line change
`@@ -5010,6 +5010,10 @@ NORET R_len_t R_BadLongVector(SEXP x, const char *file, int line)`
`5010`	`5010`
`5011`	`5011`	`/* Highly experimental resizable vector support */`
`5012`	`5012`
	`5013`	`+/* Serializing and unserializing preserves the GROWABLE bit, but`
	`5014`	`+ XTRUELENGTH is set to zero by unserialize. A vector with the`
	`5015`	`+ GROWABLE bit set but XTRUELENGTH zero is therefore considered not`
	`5016`	`+ resizeble. */`
`5013`	`5017`	`bool R_isResizable(SEXP x)`
`5014`	`5018`	`{`
`5015`	`5019`	`return isVector(x) && ! ALTREP(x) && GROWABLE_BIT_SET(x) &&`