P0876R7

example/unwind_ucontext.cpp

@@ -0,0 +1,76 @@
+
+//          Copyright Oliver Kowalke 2019.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#include <cassert>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <vector>
+
+#include <ucontext.h>
+#include <unwind.h>
+
+struct context_t {
+    ucontext_t  ucf;
+    ucontext_t  ucm;
+};
+
+struct X {
+	int	i;
+	X( int i_) : i{ i_ } { std::printf("X(%d)\n", i); }
+	~X() { std::printf("~X(%d)\n", i); }
+};
+
+_Unwind_Reason_Code stop_fn( int version,
+						_Unwind_Action actions,
+						_Unwind_Exception_Class exc_class,
+						_Unwind_Exception *exc,
+						_Unwind_Context *context,
+						void * param) {
+    context_t * ctx = ( context_t *) param;
+	if ( actions & _UA_END_OF_STACK) {
+		std::printf("end of stack, jump back\n");
+		_Unwind_DeleteException( exc);
+		if ( -1 == ::swapcontext( & ctx->ucf, & ctx->ucm) ) {
+			std::abort();
+		}
+	}
+	return _URC_NO_REASON;
+}
+
+void foo( int i, context_t * ctx) {
+	if ( 0 < i) {
+		X x{ i };
+		foo( --i, ctx);
+	} else {
+        _Unwind_Exception * exc = ( _Unwind_Exception *) std::malloc( sizeof( _Unwind_Exception) );
+        std::memset( exc, 0, sizeof( * exc) );
+        _Unwind_ForcedUnwind( exc, stop_fn, ctx);
+    	//ctx::detail::unwind( stop_fn, ctx);
+	}
+	std::printf("return from foo()\n");
+}
+
+int main( int argc, char * argv[]) {
+    context_t ctx;
+	std::vector< char > buffer(16384, '\0');
+	void * fn_stack = & buffer[0];
+	std::printf("buffer : %p\n", fn_stack);
+	fn_stack = ( char * )( ( ( ( ( uintptr_t) fn_stack) - 16) >> 4) << 4);
+	std::printf("aligned : %p\n", fn_stack);
+	if ( -1 == ::getcontext( & ctx.ucf) ) {
+		std::abort();
+	}	
+	ctx.ucf.uc_stack.ss_sp = fn_stack;
+	ctx.ucf.uc_stack.ss_size = buffer.size();
+	::makecontext( & ctx.ucf, (void(*)())( foo), 2, 5, & ctx);
+	if ( -1 == ::swapcontext( & ctx.ucm, & ctx.ucf) ) {
+		std::abort();
+	}
+    std::printf("main: done\n");
+    return EXIT_SUCCESS;
+}