[cygwin] Refactor C++ exception handling for Win32 correctness

* tests/exception.at (common.h): New file, refactored from
(module.h): Move declaration of modexc to libcommon.
Include common.h. Use explicit import/export markings for
symbols when building on win32 or cygwin.
(common.cpp): New file.
(module.cpp): Ensure correct symbols markings when including
module.h.
(lib.h): Use explicit import/export markings for symbols
when building on win32 or cygwin.
(lib.cpp): Ensure correct symbol markings when including lib.h.
(main.cpp): Include common.h.
(commands): Ensure correct symbol markings when compiling
main.cpp, and lib.cpp, and module.cpp. Add command to compile
common.cpp, and to link libcommon.la.  Add libcommon.la when
linking module.la and main.  Add command to install libcommon.la.

Signed-off-by: Charles Wilson <libtool@cwilson.fastmail.fm>

diff --git a/ChangeLog b/ChangeLog
index 18e346d6241a2f2a7d688f2101ee8a5970668cbd..79e2855daaaeff08cfb85decea8981391f1613cb 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2010-06-24  Charles Wilson  <libtool@cwilson.fastmail.fm>
+
+       [cygwin] Refactor C++ exception handling for Win32 correctness
+       * tests/exception.at (common.h): New file, refactored from
+       (module.h): Move declaration of modexc to libcommon.
+       Include common.h. Use explicit import/export markings for
+       symbols when building on win32 or cygwin.
+       (common.cpp): New file.
+       (module.cpp): Ensure correct symbols markings when including
+       module.h.
+       (lib.h): Use explicit import/export markings for symbols
+       when building on win32 or cygwin.
+       (lib.cpp): Ensure correct symbol markings when including lib.h.
+       (main.cpp): Include common.h.
+       (commands): Ensure correct symbol markings when compiling
+       main.cpp, and lib.cpp, and module.cpp. Add command to compile
+       common.cpp, and to link libcommon.la.  Add libcommon.la when
+       linking module.la and main.  Add command to install libcommon.la.
+
 2010-06-21  Gary V. Vaughan  <gary@gnu.org>
 
        Ensure getopts.m4sh is compatible with Autoconf-2.61 and newer.

diff --git a/tests/exceptions.at b/tests/exceptions.at
index aaebd0f4a7fc597192830fd19fc6d531f0d7fa5f..235597c25ab8642939ec3ea65d5b8a9850637d42 100644 (file)
--- a/tests/exceptions.at
+++ b/tests/exceptions.at
@@ -36,10 +36,66 @@ esac], [], [ignore])
 
 CPPFLAGS="$LTDLINCL $CPPFLAGS"
 
-AT_DATA([module.h],
-[[#include <exception>
+# Win32 (and cygwin) notes
+# ------------------------
+# When using C++ and Win32 DLLs, data types used in the DLL's interface
+# which are other-than-POD, must have vtables, typeinfo, and other
+# elements resolved when the client is linked.  This includes exception
+# classes.  Therefore, the exception class "modexc" thrown by the
+# dynamically-loaded module must be defined in a separate DLL, to which
+# both that module and main must be directly linked; hence, the 'common'
+# library. Not using a 'common' library in this manner represents an
+# ODR violation, unless the platform's runtime loader is capable of
+# rationalizing vague linkage items such as vtables, typeinfo, and
+# typename elements) at runtime.  The Win32 loader is not capable of
+# this, but some ELF loaders appear to be.
+#
+# Similar treatment is not necessary for liba (e.g. the libexc
+# exception class), because that library is not dynamically loaded. As a
+# consequence, vague linkage items for the class libexc are resolved at
+# link time using the vague linkage rules, for both Win32 and other
+# (e.g. ELF) platforms.
+#
+# Also, when linking a C++ DLL with another C++ DLL, some versions of
+# the GNU toolchain on Win32 (or cygwin) mistakenly re-export symbols
+# that were imported from the other DLL, when the client DLL is linked
+# using -export-all-symbols.  Similar issues MAY also arise with those
+# versions of the GNU toolchain if using the libtool link flags
+# -export-symbols LIST or -export-symbols-regex REGEX, if any symbols
+# from the dependency, rather than client, library are listed (or match
+# the regex).  However, in this test, none of these situations apply,
+# so we don't directly address it.  Otherwise, the correct mechanism
+# would be to avoid all of those flags, and instead explicitly decorate
+# all symbols with appropriate __attribute__ ((dllexport)) or
+# __attribute__ ((dllimport)) flags when building the DLLs and the
+# clients.
+#
+# For more information, see these two threads:
+#   http://lists.gnu.org/archive/html/bug-libtool/2010-06/msg00069.html
+#   http://cygwin.com/ml/cygwin/2010-06/msg00392.html
+# To sum up: C++ is complicated.
+AT_DATA([common.h],
+[[#ifndef LIBTOOL_TEST_COMMON_HEADER
+#define LIBTOOL_TEST_COMMON_HEADER
+
+#include <exception>
 #include <string>
-class modexc : public std::exception {
+
+#if defined(__CYGWIN__) || defined(_WIN32)
+# if defined(DLL_EXPORT) || defined(USING_COMMON_DLL)
+#  if defined(LIBTOOL_TEST_IN_COMMON)
+#   define COMMON_IMPEXP __attribute__ ((dllexport))
+#  else
+#   define COMMON_IMPEXP __attribute__ ((dllimport))
+#  endif
+# else
+#  define COMMON_IMPEXP
+# endif
+#else
+# define COMMON_IMPEXP
+#endif
+
+class COMMON_IMPEXP modexc : public std::exception {
 public:
   modexc (std::string str) : message (str) { }
   ~modexc () throw () { }
@@ -50,11 +106,45 @@ public:
 private:
   std::string message;
 };
-extern "C" int modfoo () throw (modexc);
+
+extern "C" int COMMON_IMPEXP common_dummy (void);
+#endif
+]])
+
+AT_DATA([common.cpp],
+[[#define LIBTOOL_TEST_IN_COMMON
+#include "common.h"
+
+extern "C"
+int common_dummy (void)
+{
+  return 0;
+}
+]])
+
+AT_DATA([module.h],
+[[#include "common.h"
+
+#if defined(__CYGWIN__) || defined(_WIN32)
+# if defined(DLL_EXPORT) || defined(USING_MODULE_DLL)
+#  if defined(LIBTOOL_TEST_IN_MODULE)
+#   define MODULE_IMPEXP __attribute__ ((dllexport))
+#  else
+#   define MODULE_IMPEXP __attribute__ ((dllimport))
+#  endif
+# else
+#  define MODULE_IMPEXP
+# endif
+#else
+# define MODULE_IMPEXP
+#endif
+
+extern "C" int MODULE_IMPEXP modfoo () throw (modexc);
 ]])
 
 AT_DATA([module.cpp],
 [[#include <iostream>
+#define LIBTOOL_TEST_IN_MODULE
 #include "module.h"
 
 int modbar (void) throw (modexc)
@@ -79,7 +169,23 @@ int modfoo (void) throw (modexc)
 AT_DATA([lib.h],
 [[#include <exception>
 #include <string>
-class libexc : public std::exception {
+
+
+#if defined(__CYGWIN__) || defined(_WIN32)
+# if defined(DLL_EXPORT) || defined(USING_LIB_DLL)
+#  if defined(LIBTOOL_TEST_IN_LIB)
+#   define LIB_IMPEXP __attribute__ ((dllexport))
+#  else
+#   define LIB_IMPEXP __attribute__ ((dllimport))
+#  endif
+# else
+#  define LIB_IMPEXP
+# endif
+#else
+# define LIB_IMPEXP
+#endif
+
+class LIB_IMPEXP libexc : public std::exception {
 public:
   libexc (std::string str) : message (str) { }
   ~libexc () throw () { }
@@ -90,11 +196,12 @@ public:
 private:
   std::string message;
 };
-int libfoo () throw (libexc);
+int LIB_IMPEXP libfoo () throw (libexc);
 ]])
 
 AT_DATA([lib.cpp],
 [[#include <iostream>
+#define LIBTOOL_TEST_IN_LIB
 #include "lib.h"
 
 int libbar (void) throw (libexc)
@@ -121,6 +228,7 @@ AT_DATA([main.cpp],
 #include <iostream>
 #include <exception>
 #include <string>
+#include "common.h"
 #include "lib.h"
 #include "module.h"
 
@@ -251,26 +359,34 @@ moddir=$inst/mod
 mkdir l m $inst $libdir $bindir $moddir
 
 # If the C++ compiler isn't capable, don't bother.
-AT_CHECK([$CXX $CPPFLAGS $CXXFLAGS -c main.cpp || exit 77], [], [ignore], [ignore])
+AT_CHECK([$CXX $CPPFLAGS $CXXFLAGS -DUSING_COMMON_DLL -DUSING_MODULE_DLL -DUSING_LIB_DLL -c main.cpp || exit 77], [], [ignore], [ignore])
 
-for file in lib.cpp module.cpp; do
-  AT_CHECK([$LIBTOOL --mode=compile --tag=CXX $CXX $CPPFLAGS $CXXFLAGS -c $file],
+AT_CHECK([$LIBTOOL --mode=compile --tag=CXX $CXX $CPPFLAGS $CXXFLAGS -c common.cpp],
+          [], [ignore], [ignore])
+AT_CHECK([$LIBTOOL --mode=compile --tag=CXX $CXX $CPPFLAGS $CXXFLAGS -c lib.cpp],
+          [], [ignore], [ignore])
+AT_CHECK([$LIBTOOL --mode=compile --tag=CXX $CXX $CPPFLAGS $CXXFLAGS -DUSING_COMMON_DLL -c module.cpp],
           [], [ignore], [ignore])
-done
+
+AT_CHECK([$LIBTOOL --mode=link --tag=CXX $CXX $CXXFLAGS $LDFLAGS -o l/libcommon.la ]dnl
+        [common.lo -no-undefined -version-info 1:0:0 -rpath $libdir],
+        [], [ignore], [ignore])
 AT_CHECK([$LIBTOOL --mode=link --tag=CXX $CXX $CXXFLAGS $LDFLAGS -o l/liba.la ]dnl
         [lib.lo -no-undefined -version-info 1:0:0 -rpath $libdir],
         [], [ignore], [ignore])
 AT_CHECK([$LIBTOOL --mode=link --tag=CXX $CXX $CXXFLAGS $LDFLAGS -o m/module.la ]dnl
-        [module.lo -module -avoid-version -no-undefined -rpath $moddir],
+        [module.lo l/libcommon.la -module -avoid-version -no-undefined -rpath $moddir],
         [], [ignore], [ignore])
 
 # We need -export-dynamic for the exception handling in modules to work.
 AT_CHECK([$LIBTOOL --mode=link --tag=CXX $CXX $CXXFLAGS $LDFLAGS -o main$EXEEXT ]dnl
-        [main.$OBJEXT l/liba.la -dlopen m/module.la $LIBLTDL -export-dynamic],
+        [main.$OBJEXT l/liba.la l/libcommon.la -dlopen m/module.la $LIBLTDL -export-dynamic],
         [], [ignore], [ignore])
 
 LT_AT_NOINST_EXEC_CHECK([./main], [-dlopen m/module.la], [], [ignore], [ignore])
 
+AT_CHECK([$LIBTOOL --mode=install cp l/libcommon.la $libdir],
+        [], [ignore], [ignore])
 AT_CHECK([$LIBTOOL --mode=install cp l/liba.la $libdir],
         [], [ignore], [ignore])
 AT_CHECK([$LIBTOOL --mode=install cp m/module.la $moddir],