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1 office 1 # woe32-dll.m4 serial 3
2 dnl Copyright (C) 2005-2006, 2011, 2015-2016 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
6  
7 dnl From Bruno Haible.
8  
9 # Add --disable-auto-import to the LDFLAGS if the linker supports it.
10 # GNU ld has an --enable-auto-import option, and it is the default on Cygwin
11 # since July 2005. But it has three fatal drawbacks:
12 # - It produces executables and shared libraries with relocations in the
13 # .text segment, defeating the principles of virtual memory.
14 # - For some constructs such as
15 # extern int var;
16 # int * const b = &var;
17 # it creates an executable that will give an error at runtime, rather
18 # than either a compile-time or link-time error or a working executable.
19 # (This is with both gcc and g++.) Whereas this code, not relying on
20 # auto-import:
21 # extern __declspec (dllimport) int var;
22 # int * const b = &var;
23 # gives a compile-time error with gcc and works with g++.
24 # - It doesn't work in some cases (references to a member field of an
25 # exported struct variable, or to a particular element of an exported
26 # array variable), requiring code modifications. One platform
27 # dictates code modifications on all platforms.
28 # See <http://www.haible.de/bruno/woe32dll.html> for more details.
29 AC_DEFUN([gl_WOE32_DLL],
30 [
31 AC_REQUIRE([AC_CANONICAL_HOST])
32 case "$host_os" in
33 mingw* | cygwin*)
34 AC_MSG_CHECKING([for auto-import of symbols])
35 AC_CACHE_VAL([gl_cv_ld_autoimport], [
36 gl_save_LDFLAGS="$LDFLAGS"
37 LDFLAGS="$LDFLAGS -Wl,--disable-auto-import"
38 AC_TRY_LINK([], [], [gl_cv_ld_autoimport=yes], [gl_cv_ld_autoimport=no])
39 LDFLAGS="$gl_save_LDFLAGS"])
40 AC_MSG_RESULT([$gl_cv_ld_autoimport])
41 if test $gl_cv_ld_autoimport = yes; then
42 LDFLAGS="$LDFLAGS -Wl,--disable-auto-import"
43 fi
44 ;;
45 esac
46 ])