diff options
Diffstat (limited to 'woe32dll/export.h')
| -rw-r--r-- | woe32dll/export.h | 49 |
1 files changed, 35 insertions, 14 deletions
diff --git a/woe32dll/export.h b/woe32dll/export.h index 999b21b8..ffcb7ab3 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 @@ -24,7 +24,15 @@ You should have received a copy of the GNU Lesser General Public License along with this program. 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. @@ -60,15 +68,28 @@ 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 @@ -76,18 +97,18 @@ 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 |