From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 11 Aug 2020 09:16:54 +0000 (-0700)
Subject: In pdumper, simplify INT_MAX computation
X-Git-Tag: emacs-28.0.90~6700
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=9e4e4775364490d31406f247237934dd7f203808;p=emacs.git

In pdumper, simplify INT_MAX computation

* src/pdumper.c (dump_read_all): Avoid unnecessary cast.
Also, round down to page size, as sysdep.c does.
Also, don’t assume INT_MAX <= UINT_MAX (!).
---

diff --git a/src/pdumper.c b/src/pdumper.c
index 6d303af77d0..fcad5242dfe 100644
--- a/src/pdumper.c
+++ b/src/pdumper.c
@@ -5065,14 +5065,13 @@ dump_read_all (int fd, void *buf, size_t bytes_to_read)
 {
   /* We don't want to use emacs_read, since that relies on the lisp
      world, and we're not in the lisp world yet.  */
-  eassert (bytes_to_read <= SSIZE_MAX);
   size_t bytes_read = 0;
   while (bytes_read < bytes_to_read)
     {
-      /* Some platforms accept only int-sized values to read.  */
-      unsigned chunk_to_read = INT_MAX;
-      if (bytes_to_read - bytes_read < chunk_to_read)
-	chunk_to_read = (unsigned) (bytes_to_read - bytes_read);
+      /* Some platforms accept only int-sized values to read.
+         Round this down to a page size (see MAX_RW_COUNT in sysdep.c).  */
+      int max_rw_count = INT_MAX >> 18 << 18;
+      size_t chunk_to_read = min (bytes_to_read - bytes_read, max_rw_count);
       ssize_t chunk = read (fd, (char *) buf + bytes_read, chunk_to_read);
       if (chunk < 0)
         return chunk;