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# woe32-dll.m4 serial 4
dnl Copyright (C) 2005-2006, 2011, 2015-2018 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.
dnl From Bruno Haible.
# Add --disable-auto-import to the LDFLAGS if the linker supports it.
# GNU ld has an --enable-auto-import option, and it is the default on Cygwin
# since July 2005. But it has three fatal drawbacks:
# - It produces executables and shared libraries with relocations in the
# .text segment, defeating the principles of virtual memory.
# - For some constructs such as
# extern int var;
# int * const b = &var;
# it creates an executable that will give an error at runtime, rather
# than either a compile-time or link-time error or a working executable.
# (This is with both gcc and g++.) Whereas this code, not relying on
# auto-import:
# extern __declspec (dllimport) int var;
# int * const b = &var;
# gives a compile-time error with gcc and works with g++.
# - It doesn't work in some cases (references to a member field of an
# exported struct variable, or to a particular element of an exported
# array variable), requiring code modifications. One platform
# dictates code modifications on all platforms.
# See <https://haible.de/bruno/woe32dll.html> for more details.
AC_DEFUN([gl_WOE32_DLL],
[
AC_REQUIRE([AC_CANONICAL_HOST])
case "$host_os" in
mingw* | cygwin*)
AC_MSG_CHECKING([for auto-import of symbols])
AC_CACHE_VAL([gl_cv_ld_autoimport], [
gl_save_LDFLAGS="$LDFLAGS"
LDFLAGS="$LDFLAGS -Wl,--disable-auto-import"
AC_TRY_LINK([], [], [gl_cv_ld_autoimport=yes], [gl_cv_ld_autoimport=no])
LDFLAGS="$gl_save_LDFLAGS"])
AC_MSG_RESULT([$gl_cv_ld_autoimport])
if test $gl_cv_ld_autoimport = yes; then
LDFLAGS="$LDFLAGS -Wl,--disable-auto-import"
fi
;;
esac
])
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