Sync woe32dll/export.h with GNU libunistring and GNU gettext.
* woe32dll/export.h: Update comments.
diff --git a/woe32dll/export.h b/woe32dll/export.h
index 2b17107..034c73b 100644
--- a/woe32dll/export.h
+++ b/woe32dll/export.h
@@ -1,5 +1,5 @@
/* Exporting symbols from Windows shared libraries.
- Copyright (C) 2006, 2011-2023 Free Software Foundation, Inc.
+ Copyright (C) 2006, 2011-2025 Free Software Foundation, Inc.
Written by Bruno Haible <bruno@clisp.org>, 2006.
This program is free software; you can redistribute it and/or modify
@@ -16,7 +16,15 @@
License along with this program; see the file COPYING.LIB. If not,
see <https://www.gnu.org/licenses/>. */
-/* There are four ways to build shared libraries on Windows:
+/* Two things are complicated when dealing with shared libraries on Windows:
+ - Exporting symbols from shared libraries (→ 'dllexport'),
+ - Referencing symbols in shared libraries from outside the library
+ (→ 'dllimport').
+ Without GNU libtool, the complications apply to both functions and variables.
+ With GNU libtool, the complications apply to variables only; GNU libtool
+ deals with the functions.
+
+ There are four ways to build shared libraries on Windows:
- Export only functions, no variables.
This has the drawback of severely affecting the programming style in use.
@@ -52,15 +60,28 @@
1. the header files are unique to this library (not shared with
other packages), and
2. the library sources are contained in one directory, making it easy
- to define a -DBUILDING_LIBXYZ flag for the library.
+ to define a -DBUILDING_LIBXYZ flag for the library (either in
+ AM_CPPFLAGS or in libxyz_la_CPPFLAGS).
Example:
- #ifdef BUILDING_LIBICONV
- #define LIBICONV_SHLIB_EXPORTED __declspec(dllexport)
- #else
- #define LIBICONV_SHLIB_EXPORTED __declspec(dllimport)
+ #if (defined _WIN32 || defined __CYGWIN__) && WOE32DLL
+ // on Windows, with --enable-shared
+ # if BUILDING_LIBXYZ // building code for libxyz
+ # if defined DLL_EXPORT // compiling object files for a DLL
+ # define LIBXYZ_SHLIB_EXPORTED __declspec(dllexport)
+ # else // compiling static object files
+ # define LIBXYZ_SHLIB_EXPORTED
+ # endif
+ # else // building code outside libxyz
+ # define LIBXYZ_SHLIB_EXPORTED __declspec(dllimport)
+ # endif
+ #else // not Windows, or --disable-shared
+ # define LIBXYZ_SHLIB_EXPORTED
#endif
- We use this technique for the libintl and the libiconv libraries.
+ We use this technique for
+ - libiconv,
+ - libintl,
+ - libgettextlib and libgettextsrc.
- Define a macro that expands to __declspec(dllimport) always, and use
it in all header files of the library. Use an explicit export list for
@@ -68,18 +89,18 @@
This is acceptable if
1. the programming language is not C++ (because the name mangling of
static struct/class fields and of variables in namespaces makes it
- hard to maintain an export list).
+ hard to maintain an export list),
+ 2. there are no constructs such as
+ extern __declspec (dllimport) int var;
+ int * const b = &var;
+ or equivalent (e.g. as in gnulib/lib/uninorm/nfc.c),
+ because these constructs give a compilation error.
The benefit of this approach is that the partitioning of the source files
into libraries (which source file goes into which library) does not
affect the source code; only the Makefiles reflect it.
The performance loss due to the unnecessary indirection for references
to variables from within the library defining the variable is acceptable.
- We use this technique for libgettextlib (because it contains many gnulib
- modules) and for libgettextsrc (because this makes it easy to move source
- code from an msg* program to libgettextsrc). The macro is called
- DLL_VARIABLE.
-
This file allows building an explicit export list. You can either
- specify the variables to be exported, and use the GNU ld option
--export-all-symbols to export all function names, or
