Update documentation of pure-space overflow

* doc/lispref/internals.texi (Garbage Collection)
(Pure Storage):
* src/alloc.c (Fgarbage_collect): Update the documentation of
pure-space overflow for when pdumper is used.  (Bug#38492)

1 files changed, 3 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 9fbd0d05739..6a17bedc75b 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6050,8 +6050,9 @@ where each entry has the form (NAME SIZE USED FREE), where:
 - FREE is the number of those objects that are not live but that Emacs
   keeps around for future allocations (maybe because it does not know how
   to return them to the OS).
-However, if there was overflow in pure space, `garbage-collect'
-returns nil, because real GC can't be done.
+However, if there was overflow in pure space, and Emacs was dumped
+using the 'unexec' method, `garbage-collect' returns nil, because
+real GC can't be done.
 See Info node `(elisp)Garbage Collection'.  */)
   (void)
 {