[Emacs-diffs] emacs-26 7648c12: Clarify a subtle issue in the Internals chapter of lispref

[Eli Zaretskii]

branch: emacs-26
commit 7648c125dfdd0232362c35c2898bbe355c874dc1
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    Clarify a subtle issue in the Internals chapter of lispref
    
    * doc/lispref/internals.texi (Writing Emacs Primitives):
    Clarify the issue with relocation of buffer or string text as
    side effect of Lisp evaluation.  (Bug#36392)
---
 doc/lispref/internals.texi | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi
index 62a102e..7cbd296 100644
--- a/doc/lispref/internals.texi
+++ b/doc/lispref/internals.texi
@@ -825,10 +825,14 @@ the type explicitly using a suitable predicate 
(@pxref{Type Predicates}).
 @code{args} refers to objects controlled by Emacs's stack-marking
 garbage collector.  Although the garbage collector does not reclaim
 objects reachable from C @code{Lisp_Object} stack variables, it may
-move non-object components of an object, such as string contents; so
-functions that access non-object components must take care to refetch
-their addresses after performing Lisp evaluation.  Lisp evaluation can
-occur via calls to @code{eval_sub} or @code{Feval}, either directly or
+move some of the components of an object, such as the contents of a
+string or the text of a buffer.  Therefore, functions that access
+these components must take care to refetch their addresses after
+performing Lisp evaluation.  This means that instead of keeping C
+pointers to string contents or buffer text, the code should keep the
+buffer or string position, and recompute the C pointer from the
+position after performing Lisp evaluation.  Lisp evaluation can occur
+via calls to @code{eval_sub} or @code{Feval}, either directly or
 indirectly.
 
 @cindex @code{maybe_quit}, use in Lisp primitives