* cppfiles.c (read_include_file): Add comment.

From-SVN: r47369

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1a22e47bf9772ce700ca3f1563e0fd4754f01909..2d6093552dcc6a644253c1231e6c9d6e1e6b5873 100644 (file)
--- 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 f0d85d9bf3759048b521b7dd02be3427cff1babc..65bcf62e07b91eadccbb6e48ce5f4348cec99c98 100644 (file)
--- 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)
        {