From: Zack Weinberg <zack@codesourcery.com>
Date: Tue, 27 Nov 2001 07:42:10 +0000 (+0000)
Subject: * cppfiles.c (read_include_file): Add comment.
X-Git-Tag: prereleases/libstdc++-3.0.95~706
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=07e96fc688ba9fcc49c0e71ce8a3b484feacac52;p=thirdparty%2Fgcc.git

* cppfiles.c (read_include_file): Add comment.

From-SVN: r47369
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1a22e47bf977..2d6093552dcc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2001-11-27  Zack Weinberg  <zack@codesourcery.com>
+
+	* cppfiles.c (read_include_file): Add comment.
+
 2001-11-26  Richard Henderson  <rth@redhat.com>
 
 	* toplev.c (rest_of_compilation): Call free_bb_for_insn before exit.
diff --git a/gcc/cppfiles.c b/gcc/cppfiles.c
index f0d85d9bf375..65bcf62e07b9 100644
--- a/gcc/cppfiles.c
+++ b/gcc/cppfiles.c
@@ -382,6 +382,11 @@ read_include_file (pfile, inc)
       if (pagesize == -1)
 	pagesize = getpagesize ();
 
+      /* Use mmap if the file is big enough to be worth it (controlled
+	 by MMAP_THRESHOLD) and if we can safely count on there being
+	 at least one readable NUL byte after the end of the file's
+	 contents.  This is true for all tested operating systems when
+	 the file size is not an exact multiple of the page size.  */
       if (size / pagesize >= MMAP_THRESHOLD
 	  && (size % pagesize) != 0)
 	{