Do not force exceptions and rtti when using GNU libstdc++

This patch changes the default exported flags for both
gnustl_static and gnustl_shared. Previously, they were always
set to -fexceptions and -frtti, but this resulted in a few
problems.

Now, the flags are empty by default, but you can use
APP_GNUSTL_FORCE_CPP_FEATURES in your Application.mk to
revert to the old behaviour, in case you need it.

+ Add four unit tests to check that the build system works
  correctly with regards to this new variable definition

+ Documentation updates.

+ Modify tests/run-tests.sh to recognize a 'BUILD_SHOULD_FAIL'
  tag in a unit test directory. If such a file is present,
  the build _should_ fail for the test to pass.

  This is required because there is no way to reliably detect
  at compile time that -frtti is _not_ used, so we actually
  require the opposite from our unit test sources.
  (see gnustl-force-none and gnustl-force-exceptions).

Change-Id: Ia6fd236284c942bc0cb8fc0b49d9344ab68fe7ee

docs/APPLICATION-MK.html

@@ -173,6 +173,35 @@ APP_STL
 
     For more information on the subject, please read docs/CPLUSPLUS-SUPPORT.html
 
+APP_GNUSTL_FORCE_CPP_FEATURES
+    In prior NDK versions, the simple fact of using the GNU libstdc++
+    runtime (i.e. by setting APP_STL to either 'gnustl_static' or
+    'gnustl_shared') enforced the support for exceptions and RTTI in all
+    generated machine code. This could be problematic in specific, but rare,
+    cases, and also generated un-necessarily bigger code for projects that
+    don't require these features.
+
+    This bug was fixed in NDK r7b, but this means that if your code requires
+    exceptions or RTTI, it should now explicitely say so, either in your
+    APP_CPPFLAGS, or your LOCAL_CPPFLAGS / LOCAL_CPP_FEATURES definitions.
+
+    To make it easier to port projects to NDK r7b and later, one can
+    optionally defined APP_GNUSTL_CPP_FEATURES to contain one or more of the
+    following values:
+
+       exceptions    -> to enforce exceptions support for all modules.
+       rtti          -> to enforce rtti support for all modules.
+
+    For example, to get the exact same behaviour than NDK r7:
+
+       APP_GNUSTL_FORCE_CPP_FEATURES := exceptions rtti
+
+    IMPORTANT: This variable is provided here as a convenience to make it
+               easier to transition to a newer version of the NDK. It will
+               be removed in a future revision. We thus encourage all
+               developers to modify the module definitions properly instead
+               of relying on it here.
+
 A trivial Application.mk file would be:
 
 -------------- cut here -------------------------

docs/CHANGES.html

@@ -46,6 +46,18 @@ IMPORTANT BUG FIXES:
 
 OTHER CHANGES:
 
+- When your application uses the GNU libstdc++ runtime, the compiler will
+  no longer forcibly enable exceptions and RTTI. This will result in smaller
+  code.
+
+  If you need these features, you need to do either one of these:
+
+     1/ Enable exceptions and/or RTTI explicitely in your modules or
+        Application.mk (recommended)
+
+     2/ Define APP_GNUSTL_FORCE_CPP_FEATURES to 'exceptions', 'rtti' or both
+        in your Application.mk. See docs/APPLICATION-MK.html for more details.
+
 - ndk-gdb now works properly when your application has private services
   running in independent processes. More specifically it will debug the
   main application process, instead of the first process listed by 'ps'

docs/CPLUSPLUS-SUPPORT.html

@@ -86,7 +86,7 @@ If you insist on using it, read the "RTTI Support" and
 
 
 I.3. STLport runtime:
-- - - - - - - - - - - 
+- - - - - - - - - - -
 
 This is a port of STLport (http://www.stlport.org) that can be used on
 Android. It will provide you with a complete set of C++ standard library
@@ -192,7 +192,7 @@ This is likely to result in code that doesn't work correctly, for example:
   - exceptions raised in libfoo.so cannot be caught in libbar.so (and may
     simply crash the program).
 
-  - the buffering of cout not working properly
+  - the buffering of std::cout not working properly
 
 This problem also happens if you want to link an executable and a shared
 library to the same static library.
@@ -253,8 +253,7 @@ IV. Future Plans:
 -----------------
 
   - Add exceptions support to GAbi++
-  - Make STLport use GAbi++ to gain RTTI support (and potentially exceptions too)
-  - Shared GNU libstdc++ support
+  - Add exceptions support to STLport (once it is in GAbi++)
   - uSTL support?
 
 </pre></body></html>

sources/cxx-stl/gnu-libstdc++/Android.mk

 LOCAL_PATH := $(call my-dir)
 
+# Compute the compiler flags to export by the module.
+# This is controlled by the APP_GNUSTL_FORCE_CPP_FEATURES variable.
+# See docs/APPLICATION-MK.html for all details.
+#
+gnustl_exported_cppflags := $(strip \
+  $(if $(filter exceptions,$(APP_GNUSTL_FORCE_CPP_FEATURES)),-fexceptions)\
+  $(if $(filter rtti,$(APP_GNUSTL_FORCE_CPP_FEATURES)),-frtti))
+
+# Include path to export
+gnustl_exported_c_includes := $(LOCAL_PATH)/include $(LOCAL_PATH)/libs/$(TARGET_ARCH_ABI)/include
+
 include $(CLEAR_VARS)
 LOCAL_MODULE := gnustl_static
 LOCAL_SRC_FILES := libs/$(TARGET_ARCH_ABI)/libgnustl_static.a
-LOCAL_EXPORT_CPPFLAGS := -fexceptions -frtti
-LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include \
-                           $(LOCAL_PATH)/libs/$(TARGET_ARCH_ABI)/include
+LOCAL_EXPORT_CPPFLAGS := $(gnustl_exported_cppflags)
+LOCAL_EXPORT_C_INCLUDES := $(gnustl_exported_c_includes)
 include $(PREBUILT_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)
 LOCAL_MODULE := gnustl_shared
 LOCAL_SRC_FILES := libs/$(TARGET_ARCH_ABI)/libgnustl_shared.so
-LOCAL_EXPORT_CPPFLAGS := -fexceptions -frtti
-LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include \
-                           $(LOCAL_PATH)/libs/$(TARGET_ARCH_ABI)/include
+LOCAL_EXPORT_CPPFLAGS := $(gnustl_exported_cppflags)
+LOCAL_EXPORT_C_INCLUDES := $(gnustl_exported_c_includes)
 LOCAL_EXPORT_LDLIBS := $(call host-path,$(LOCAL_PATH)/libs/$(TARGET_ARCH_ABI)/libsupc++.a)
 include $(PREBUILT_SHARED_LIBRARY)

tests/build/gnustl-force-all/jni/Android.mk

+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := test_gnustl_forced_all
+LOCAL_SRC_FILES := forced_all.cpp
+include $(BUILD_EXECUTABLE)

tests/build/gnustl-force-all/jni/Application.mk

+APP_STL := gnustl_static
+APP_GNUSTL_FORCE_CPP_FEATURES := exceptions rtti

tests/build/gnustl-force-all/jni/forced_all.cpp

+/* This file should be compiled with exceptions and without RTTI */
+#ifndef __EXCEPTIONS
+#error This source file SHOULD be built with -fexceptions!
+#endif
+
+#include <typeinfo>
+#include <stdio.h>
+
+class Foo { int x; };
+
+int main(void) {
+    printf("%p\n", typeid(Foo)); // will fail without -frtti
+    return 0;
+}

tests/build/gnustl-force-exceptions/jni/Android.mk

+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := test_gnustl_forced_exceptions
+LOCAL_SRC_FILES := forced_exceptions.cpp
+include $(BUILD_EXECUTABLE)
+

tests/build/gnustl-force-exceptions/jni/Application.mk

+APP_STL := gnustl_static
+APP_GNUSTL_FORCE_CPP_FEATURES := exceptions

tests/build/gnustl-force-exceptions/jni/forced_exceptions.cpp

+// This file should FAIL to build iff exceptions are enabled and RTTI is disabled
+#ifndef __EXCEPTIONS
+int main(void) { return 0; }
+#else // !exceptions
+#include <typeinfo>
+#include <stdio.h>
+
+class Foo { int x; };
+
+int main(void) {
+    printf("%p\n", typeid(Foo)); // will fail without -frtti
+    return 0;
+}
+#endif

tests/build/gnustl-force-none/jni/Android.mk

+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := test_gnustl_force_none
+LOCAL_SRC_FILES := force_none.cpp
+include $(BUILD_EXECUTABLE)

tests/build/gnustl-force-none/jni/Application.mk

+APP_STL := gnustl_static
+APP_GNUSTL_FORCE_CPP_FEATURES := # empty
\ No newline at end of file

tests/build/gnustl-force-none/jni/force_none.cpp

+// This program should FAIL to build iff exceptions and RTTI are disabled.
+#ifdef __EXCEPTIONS
+// can't fail to build here
+int main(void) { return 0; }
+#else // !exceptions
+#include <typeinfo>
+#include <stdio.h>
+
+class Foo { int x; };
+
+int main(void) {
+    printf("%p\n", typeid(Foo)); // will fail with RTTI
+    return 0;
+}
+#endif

tests/build/gnustl-force-rtti/jni/Android.mk

+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := test_gnustl_forced_rtti
+LOCAL_SRC_FILES := forced_rtti.cpp
+include $(BUILD_EXECUTABLE)

tests/build/gnustl-force-rtti/jni/Application.mk

+APP_STL := gnustl_static
+APP_GNUSTL_FORCE_CPP_FEATURES := rtti
\ No newline at end of file

tests/build/gnustl-force-rtti/jni/forced_rtti.cpp

+/* This file should be compiled without exceptions and with RTTI */
+#ifdef __EXCEPTIONS
+#error This source file SHOULD NOT be built with -fexceptions!
+#endif
+
+#include <typeinfo>
+#include <stdio.h>
+
+class Foo { int x; };
+
+int main(void) {
+    printf("%p\n", typeid(Foo)); // will fail without -frtti
+    return 0;
+}

tests/device/gnustl-shared-1/jni/Application.mk

 APP_STL := gnustl_shared
 APP_ABI := all
+APP_CPPFLAGS := -fexceptions

tests/run-tests.sh

@@ -405,7 +405,16 @@ build_project ()
     fi
     rm -rf "$DIR" && cp -r "$1" "$DIR"
     (cd "$DIR" && run_ndk_build $NDK_BUILD_FLAGS)
-    if [ $? != 0 ] ; then
+    RET=$?
+    if [ -f "$1/BUILD_SHOULD_FAIL" ]; then
+        if [ $RET = 0 ]; then
+            echo "!!! FAILURE: BUILD SHOULD HAVE FAILED [$1]"
+            exit 1
+        fi
+        log "!!! SUCCESS: BUILD FAILED AS EXPECTED [$(basename $1)]"
+        RET=0
+    fi
+    if [ $RET != 0 ] ; then
         echo "!!! BUILD FAILURE [$1]!!! See $NDK_LOGFILE for details or use --verbose option!"
         exit 1
     fi