non-UB type punning function

brainboxdotcc · Oct 4, 2024 · 5838f50 · 5838f50
1 parent 27c1b07
commit 5838f50
Show file tree

Hide file tree

Showing 5 changed files with 34 additions and 8 deletions.
diff --git a/include/dpp/convert_to.h b/include/dpp/convert_to.h
@@ -0,0 +1,25 @@
+#include <cstring>
+#include <array>
+#include <memory>
+#include <new>
+
+/**
+ * @brief Safely convert one type to another without UB.
+ * This is produces identical assembly to reinterpret_cast.
+ *
+ * @param ptr Input pointer type
+ * @return Converted pointer type
+ *
+ * @tparam IN source type
+ * @tparam OUT destination type
+ *
+ * This is essentially std::start_lifetime_as(), without
+ * the requirement for C++23.
+ *
+ * @note Based on code by Krystian Stasiowski
+ * (https://github.com/sdkrystian)
+ */
+template<typename IN, typename OUT> OUT* convert_to(IN* ptr)
+{
+	return std::launder(static_cast<OUT*>(std::memmove(ptr, ptr, sizeof(OUT))));
+}
diff --git a/include/dpp/dpp.h b/include/dpp/dpp.h
@@ -75,3 +75,4 @@
 #include <dpp/timed_listener.h>
 #include <dpp/collector.h>
 #include <dpp/bignum.h>
+#include <dpp/convert_to.h>
diff --git a/library-vcpkg/CMakeLists.txt b/library-vcpkg/CMakeLists.txt
@@ -67,8 +67,8 @@ target_compile_options(
 	PRIVATE
 		"$<$<PLATFORM_ID:Windows>:$<$<CONFIG:Debug>:/sdl;/Od;/DEBUG;/MP;/DFD_SETSIZE=1024>>"
 		"$<$<PLATFORM_ID:Windows>:$<$<CONFIG:Release>:/O2;/Oi;/Oy;/GL;/Gy;/sdl;/MP;/DFD_SETSIZE=1024>>"
-		"$<$<PLATFORM_ID:Linux>:$<$<CONFIG:Debug>:-fPIC;-Wall;-Wempty-body;-Wno-psabi;-Wunknown-pragmas;-Wignored-qualifiers;-Wimplicit-fallthrough;-Wmissing-field-initializers;-Wsign-compare;-Wtype-limits;-Wuninitialized;-Wshift-negative-value;-pthread;-g;-Og;-fPIC>>"
-		"$<$<PLATFORM_ID:Linux>:$<$<CONFIG:Release>:-fPIC;-Wall;-Wempty-body;-Wno-psabi;-Wunknown-pragmas;-Wignored-qualifiers;-Wimplicit-fallthrough;-Wmissing-field-initializers;-Wsign-compare;-Wtype-limits;-Wuninitialized;-Wshift-negative-value;-pthread;-O3;-fPIC>>"
+		"$<$<PLATFORM_ID:Linux>:$<$<CONFIG:Debug>:-fPIC;-Wall;-Wempty-body;-Wno-class-memaccess;-Wno-psabi;-Wunknown-pragmas;-Wignored-qualifiers;-Wimplicit-fallthrough;-Wmissing-field-initializers;-Wsign-compare;-Wtype-limits;-Wuninitialized;-Wshift-negative-value;-pthread;-g;-Og;-fPIC>>"
+		"$<$<PLATFORM_ID:Linux>:$<$<CONFIG:Release>:-fPIC;-Wall;-Wempty-body;-Wno-class-memaccess;-Wno-psabi;-Wunknown-pragmas;-Wignored-qualifiers;-Wimplicit-fallthrough;-Wmissing-field-initializers;-Wsign-compare;-Wtype-limits;-Wuninitialized;-Wshift-negative-value;-pthread;-O3;-fPIC>>"
 		"${AVX_FLAG}"
 )
 

diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
@@ -216,7 +216,7 @@ if(MSVC)
 	endif()
 	string(REGEX REPLACE "/W[1|2|3|4]" "/W3" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 else()
-	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -Wall -Wno-unused-private-field -Wno-psabi -Wempty-body -Wignored-qualifiers -Wimplicit-fallthrough -Wmissing-field-initializers -Wsign-compare -Wtype-limits -Wuninitialized -Wshift-negative-value -pthread")
+	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -Wall -Wno-class-memaccess -Wno-unused-private-field -Wno-psabi -Wempty-body -Wignored-qualifiers -Wimplicit-fallthrough -Wmissing-field-initializers -Wsign-compare -Wtype-limits -Wuninitialized -Wshift-negative-value -pthread")
 	set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Og")
 
 	if (NOT MINGW)

diff --git a/src/dpp/voice/enabled/discover_ip.cpp b/src/dpp/voice/enabled/discover_ip.cpp
@@ -22,6 +22,7 @@
 
 #include <dpp/exception.h>
 #include <dpp/discordvoiceclient.h>
+#include <dpp/convert_to.h>
 #include "enabled.h"
 
 #ifdef _WIN32
@@ -88,23 +89,22 @@ std::string discord_voice_client::discover_ip() {
 
 	if (socket.fd >= 0) {
 		sockaddr_in servaddr{};
-		memset(&servaddr, 0, sizeof(sockaddr_in));
 		servaddr.sin_family = AF_INET;
 		servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
 		servaddr.sin_port = htons(0);
-		if (bind(socket.fd, (sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
+		if (bind(socket.fd, convert_to<sockaddr_in, const sockaddr>(&servaddr), sizeof(servaddr)) < 0) {
 			log(ll_warning, "Could not bind socket for IP discovery");
 			return "";
 		}
 		memset(&servaddr, 0, sizeof(servaddr));
 		servaddr.sin_family = AF_INET;
 		servaddr.sin_port = htons(this->port);
 		servaddr.sin_addr.s_addr = inet_addr(this->ip.c_str());
-		if (::connect(socket.fd, (const sockaddr*)&servaddr, sizeof(sockaddr_in)) < 0) {
+		if (::connect(socket.fd, convert_to<sockaddr_in, const sockaddr>(&servaddr), sizeof(sockaddr_in)) < 0) {
 			log(ll_warning, "Could not connect socket for IP discovery");
 			return "";
 		}
-		if (::send(socket.fd, reinterpret_cast<const char*>(&discovery), sizeof(discovery), 0) == -1) {
+		if (::send(socket.fd, convert_to<ip_discovery_packet, const char>(&discovery), sizeof(discovery), 0) == -1) {
 			log(ll_warning, "Could not send packet for IP discovery");
 			return "";
 		}
@@ -121,7 +121,7 @@ std::string discord_voice_client::discover_ip() {
 				log(ll_warning, "Timed out in IP discovery");
 				return "";
 			default:
-				if (recv(socket.fd, reinterpret_cast<char*>(&discovery), sizeof(discovery), 0) == -1) {
+				if (recv(socket.fd, convert_to<ip_discovery_packet, char>(&discovery), sizeof(discovery), 0) == -1) {
 					log(ll_warning, "Could not receive packet for IP discovery");
 					return "";
 				}