A6: WIP

1 files changed, 68 insertions, 0 deletions

diff --git a/a6/noalloc.cc b/a6/noalloc.cc
new file mode 100644
index 0000000..0da4025
--- /dev/null
+++ b/a6/noalloc.cc
@@ -0,0 +1,68 @@
+#include <iostream>
+#include <functional>
+
+// Universal allocator
+namespace memory
+{
+void* ptr{};
+}
+
+void* operator new([[maybe_unused]]std::size_t n) // throw(std::bad_alloc) - don't throw
+{
+	std::cout << "new\n";
+	// Just return the supplied stack pointer
+	return memory::ptr;
+}
+
+void operator delete(void*) throw()
+{
+	std::cout << "delete\n";
+	// Do nothing. actual memory is allocated on the stack
+}
+
+void operator delete(void*, std::size_t) throw()
+{
+	std::cout << "delete[]\n";
+	// Do nothing. actual memory is allocated on the stack
+}
+
+//void foo() __attribute__((noinline))
+int main()
+{
+	char buf[256];
+	memory::ptr = buf;
+
+	std::cout << " ** strings:\n";
+	{ // strings
+		// now this is ok:
+		std::string str(32, 'a');
+		std::cout << str << '\n';
+
+		std::string str2(24, 'b');
+		std::cout << str << '\n'; // the contents of str has been overwritten
+
+		// this will also allocate, but supply the same buffer - ok
+		str = "hello world hello world hello world";
+
+		// this is also ok, but due to SSO
+		std::string sso{"hello"};
+	}
+
+	std::cout << " ** lambdas:\n";
+	{ // lambdas
+		std::function<int()> f;
+		{
+			char foo[16]{};
+			f = [=]()__attribute__((noinline)) // capture up 16 bytes - ok
+				{
+					int i = 0;
+					for(auto v : foo)
+					{
+						i += v;
+					}
+					return i;
+				}; // capture foo by copy - inlined
+		}
+		[[maybe_unused]]auto x = f();
+	}
+}