cxx: Simplify C++ exception wrapper functions

The wrapper functions (e.g., 'Unwind_*' and friends) now have the same signature
as the original function in 'libgcc', reside in a separate C file which is
archived to cxx.lib.a. In supc++.o we prefix the wrapped functions with '_cxx_'.

This also enables support for riscv.

related to #1880

repos/base/lib/mk/cxx.mk

@@ -1,9 +1,9 @@
-CXX_SRC_CC += misc.cc new_delete.cc malloc_free.cc exception.cc guard.cc unwind.cc
-
+CXX_SRC_CC += misc.cc new_delete.cc malloc_free.cc exception.cc guard.cc
 # We need the libsupc++ include directory
 STDINC = yes
 
 vpath %.cc $(BASE_DIR)/src/base/cxx
+vpath %.c  $(BASE_DIR)/src/base/cxx
 
 #
 # Here we define all symbols we want to hide in libsupc++ and libgcc_eh
@@ -43,10 +43,11 @@ LIBCXX_GCC = $(shell $(CUSTOM_CXX_LIB) $(CC_MARCH) -print-file-name=libsupc++.a)
 # Dummy target used by the build system
 #
 SRC_S         = supc++.o
+SRC_C         = unwind.o
 CXX_SRC       = $(sort $(CXX_SRC_CC))
 CXX_OBJECTS   = $(addsuffix .o,$(basename $(CXX_SRC)))
 LOCAL_SYMBOLS = $(patsubst %,--localize-symbol=%,$(LIBC_SYMBOLS))
-REDEF_SYMBOLS = $(foreach S, $(EH_SYMBOLS), --redefine-sym $(S)=_cxx_$(S) --redefine-sym __cxx_$(S)=$(S))
+REDEF_SYMBOLS = $(foreach S, $(EH_SYMBOLS), --redefine-sym $(S)=_cxx_$(S))
 
 #
 # Prevent symbols of the gcc support libs from being discarded during 'ld -r'

repos/base/src/base/cxx/unwind.c

@@ -0,0 +1,48 @@
+/*
+ * \brief  Wrapper for symbols required by libgcc_eh's exception handling
+ * \author Sebastian Sumpf
+ * \date   2015-09-04
+ *
+ * The wrapper always calls a function with prefix '_cxx'. In 'cxx.mk' we prefix
+ * the wrapped functions with '_cxx'.  This whole procedure became necessary
+ * since the wrapped symbols are marked 'GLOBAL', 'HIDDEN' in libgcc_eh.a and
+ * thus ligcc_eh had to be linked to *all* binaries. In shared libaries this
+ * became unfeasible since libgcc_eh uses global data which might not be
+ * initialized during cross-library interaction.  The clean way to go would be
+ * to link libgcc_s.so to DSOs and dynamic binaries, unfortunally ligcc_s
+ * requires libc6 in the current Genode tool chain.
+ */
+
+/*
+ * Copyright (C) 2011-2013 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Unwind function found in all binaries */
+void _cxx__Unwind_Resume(void *exc)  __attribute__((weak));
+void _Unwind_Resume(void *exc) {
+	_cxx__Unwind_Resume(exc); }
+
+void _cxx__Unwind_DeleteException(void *exc) __attribute__((weak));
+void _Unwind_DeleteException(void *exc) {
+	_cxx__Unwind_DeleteException(exc); }
+
+/* Special ARM-EABI personality functions */
+#ifdef __ARM_EABI__
+
+int _cxx___aeabi_unwind_cpp_pr0(int state, void *block, void *context) __attribute__((weak));
+int __aeabi_unwind_cpp_pr0(int state, void *block, void *context) {
+	return _cxx___aeabi_unwind_cpp_pr0(state, block, context); }
+
+int  _cxx___aeabi_unwind_cpp_pr1(int state, void *block, void *context) __attribute__((weak));
+int __aeabi_unwind_cpp_pr1(int state, void *block, void *context) {
+	return _cxx___aeabi_unwind_cpp_pr1(state, block, context); }
+
+/* Unwind functions found in some binaries */
+void  _cxx__Unwind_Complete(void *exc)  __attribute__((weak));
+void _Unwind_Complete(void *exc) {
+	_cxx__Unwind_Complete(exc); }
+
+#endif /* __ARM_EABI__ */

repos/base/src/base/cxx/unwind.cc

@@ -1,53 +0,0 @@
-/*
- * \brief  Wrapper for symbols required by libgcc_eh's exception handling
- * \author Sebastian Sumpf
- * \date   2011-07-20
- *
- * The actual wrapper function is prefixed with '__cxx', the wrapper always
- * calls a function with prefix '_cxx' (note the missing '_'). In 'cxx.mk'
- * we remove the leading '__cxx' from the wrapper which than becomes the symbol
- * of the wrapped function, in turn the wrapped function is prefixed with '_cxx'.
- * This whole procedure became necessary since the wrapped symbols are marked
- * 'GLOBAL', 'HIDDEN' in libgcc_eh.a and thus ligcc_eh had to be linked to *all*
- * binaries. In shared libaries this became unfeasible since libgcc_eh uses
- * global data which might not be initialized during cross-library interaction.
- * The clean way to go would be to link libgcc_s.so to DSOs and dynamic
- * binaries, unfortunally ligcc_s requires libc6 in the current Genode tool
- * chain.
- */
-
-/*
- * Copyright (C) 2011-2013 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU General Public License version 2.
- */
-
-extern "C" {
-
-	/* Unwind function found in all binaries */
-	void  _cxx__Unwind_Resume(void *exc)  __attribute__((weak));
-	void __cxx__Unwind_Resume(void *exc) {
-		_cxx__Unwind_Resume(exc); }
-
-	void  _cxx__Unwind_DeleteException(void *exc)  __attribute__((weak));
-	void __cxx__Unwind_DeleteException(void *exc) {
-		_cxx__Unwind_DeleteException(exc); }
-
-	/* Special ARM-EABI personality functions */
-#ifdef __ARM_EABI__
-
-	int  _cxx___aeabi_unwind_cpp_pr0(int state, void *block, void *context) __attribute__((weak));
-	int __cxx___aeabi_unwind_cpp_pr0(int state, void *block, void *context) {
-		return _cxx___aeabi_unwind_cpp_pr0(state, block, context); }
-
-	int  _cxx___aeabi_unwind_cpp_pr1(int state, void *block, void *context) __attribute__((weak));
-	int __cxx___aeabi_unwind_cpp_pr1(int state, void *block, void *context) {
-		return _cxx___aeabi_unwind_cpp_pr1(state, block, context); }
-
-	/* Unwind functions found in some binaries */
-	void  _cxx__Unwind_Complete(void *exc)  __attribute__((weak));
-	void __cxx__Unwind_Complete(void *exc) {
-		_cxx__Unwind_Complete(exc); }
-#endif
-}