Document a pitfall.

diff --git a/ChangeLog b/ChangeLog
index 2483b344b19431c029ac77aaba5e67f348a41edd..4266b9d5e5cc9c55186afc6f2490ed677bcd96b4 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2008-03-10  Bruno Haible  <bruno@clisp.org>
+
+       * m4/include_next.m4 (gl_CHECK_NEXT_HEADERS): Document a restriction.
+       * m4/absolute-header.m4 (gl_ABSOLUTE_HEADER): Likewise.
+       Reported by Peter O'Gorman <bug-gnulib@mlists.thewrittenword.com>.
+
 2008-03-10  Bruno Haible  <bruno@clisp.org>
 
        * modules/stdlib (Depends-on): Add include_next, remove

diff --git a/m4/absolute-header.m4 b/m4/absolute-header.m4
index 5b7a2fc35f08d6bddc2f58eb0a1f887c2f8364a7..e039f0c6e76a24795537d7303a6ed65f12dc4048 100644 (file)
--- a/m4/absolute-header.m4
+++ b/m4/absolute-header.m4
@@ -1,5 +1,5 @@
-# absolute-header.m4 serial 7
-dnl Copyright (C) 2006, 2007 Free Software Foundation, Inc.
+# absolute-header.m4 serial 8
+dnl Copyright (C) 2006-2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -16,6 +16,9 @@ dnl From Derek Price.
 # The three "///" are to pacify Sun C 5.8, which otherwise would say
 # "warning: #include of /usr/include/... may be non-portable".
 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
+# Note: This macro assumes that the header file is not empty after
+# preprocessing, i.e. it does not only define preprocessor macros but also
+# provides some type/enum definitions or function/variable declarations.
 AC_DEFUN([gl_ABSOLUTE_HEADER],
 [AC_LANG_PREPROC_REQUIRE()dnl
 AC_FOREACH([gl_HEADER_NAME], [$1],

diff --git a/m4/include_next.m4 b/m4/include_next.m4
index 7ce472bc0a0b9b9d7a4c4c9ccca8b8a680e07eca..7c08e9319bf83cdb3ca6ee3b16ad679fc292fe3f 100644 (file)
--- a/m4/include_next.m4
+++ b/m4/include_next.m4
@@ -1,5 +1,5 @@
-# include_next.m4 serial 4
-dnl Copyright (C) 2006, 2007 Free Software Foundation, Inc.
+# include_next.m4 serial 5
+dnl Copyright (C) 2006-2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -63,6 +63,9 @@ EOF
 # The three "///" are to pacify Sun C 5.8, which otherwise would say
 # "warning: #include of /usr/include/... may be non-portable".
 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
+# Note: This macro assumes that the header file is not empty after
+# preprocessing, i.e. it does not only define preprocessor macros but also
+# provides some type/enum definitions or function/variable declarations.
 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
 [
   AC_REQUIRE([gl_INCLUDE_NEXT])