Don't use unreliable linker options on native Windows.

1 files changed, 45 insertions, 0 deletions

diff --git a/m4/woe32-dll.m4 b/m4/woe32-dll.m4
new file mode 100644
index 0000000..6b5a037
--- /dev/null
+++ b/m4/woe32-dll.m4
@@ -0,0 +1,45 @@
+# woe32-dll.m4 serial 2
+dnl Copyright (C) 2005-2006 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.
+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
+])