fixes for UBSAN warnings (#4223)

Problem: UBSAN shows warnings

Solution: fix alignment issues and signed to unsigned conversion

CMakeLists.txt

@@ -70,7 +70,7 @@ endif()
 option(ENABLE_UBSAN "Build with undefined behavior sanitizer" OFF)
 if(ENABLE_UBSAN)
   message(STATUS "Instrumenting with Undefined Behavior Sanitizer")
-  set(CMAKE_BUILD_TYPE "RelWithDebInfo")
+  set(CMAKE_BUILD_TYPE "Debug")
   set(UBSAN_FLAGS "${UBSAN_FLAGS} -fno-omit-frame-pointer")
   set(UBSAN_FLAGS "${UBSAN_FLAGS} -fsanitize=undefined")
   set(UBSAN_FLAGS "${UBSAN_FLAGS} -fsanitize=implicit-conversion")
@@ -464,6 +464,7 @@ message(STATUS "Using polling method in zmq_poll(er)_* API: ${API_POLLER}")
 string(TOUPPER ${API_POLLER} UPPER_API_POLLER)
 set(ZMQ_POLL_BASED_ON_${UPPER_API_POLLER} 1)
 
+# special alignment settings
 execute_process(
   COMMAND getconf LEVEL1_DCACHE_LINESIZE
   OUTPUT_VARIABLE CACHELINE_SIZE
@@ -476,6 +477,7 @@ else()
   set(ZMQ_CACHELINE_SIZE ${CACHELINE_SIZE})
 endif()
 message(STATUS "Using ${ZMQ_CACHELINE_SIZE} bytes alignment for lock-free data structures")
+check_cxx_symbol_exists(posix_memalign stdlib.h HAVE_POSIX_MEMALIGN)
 
 if(NOT CYGWIN)
   # TODO cannot we simply do 'if(WIN32) set(ZMQ_HAVE_WINDOWS ON)' or similar?

builds/cmake/platform.hpp.in

@@ -16,6 +16,7 @@
 #cmakedefine ZMQ_POLL_BASED_ON_SELECT
 #cmakedefine ZMQ_POLL_BASED_ON_POLL
 
+#cmakedefine HAVE_POSIX_MEMALIGN @HAVE_POSIX_MEMALIGN@
 #cmakedefine ZMQ_CACHELINE_SIZE @ZMQ_CACHELINE_SIZE@
 
 #cmakedefine ZMQ_FORCE_MUTEXES

src/command.hpp

@@ -33,6 +33,7 @@
 #include <string>
 #include "stdint.hpp"
 #include "endpoint.hpp"
+#include "platform.hpp"
 
 namespace zmq
 {
@@ -44,12 +45,7 @@ class socket_base_t;
 
 //  This structure defines the commands that can be sent between threads.
 
-#ifdef _MSC_VER
+struct command_t
-#pragma warning(push)
-#pragma warning(disable : 4324) // C4324: alignment padding warnings
-__declspec(align (64))
-#endif
-  struct command_t
 {
     //  Object to process the command.
     zmq::object_t *destination;
@@ -216,9 +212,12 @@ __declspec(align (64))
     } args;
 #ifdef _MSC_VER
 };
-#pragma warning(pop)
 #else
-} __attribute__ ((aligned (64)));
+}
+#ifdef HAVE_POSIX_MEMALIGN
+__attribute__ ((aligned (ZMQ_CACHELINE_SIZE)))
+#endif
+;
 #endif
 }
 

src/epoll.cpp

@@ -131,7 +131,7 @@ void zmq::epoll_t::reset_pollin (handle_t handle_)
 {
     check_thread ();
     poll_entry_t *pe = static_cast<poll_entry_t *> (handle_);
-    pe->ev.events &= ~(static_cast<short> (EPOLLIN));
+    pe->ev.events &= ~(static_cast<uint32_t> (EPOLLIN));
     const int rc = epoll_ctl (_epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
     errno_assert (rc != -1);
 }
@@ -149,7 +149,7 @@ void zmq::epoll_t::reset_pollout (handle_t handle_)
 {
     check_thread ();
     poll_entry_t *pe = static_cast<poll_entry_t *> (handle_);
-    pe->ev.events &= ~(static_cast<short> (EPOLLOUT));
+    pe->ev.events &= ~(static_cast<uint32_t> (EPOLLOUT));
     const int rc = epoll_ctl (_epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
     errno_assert (rc != -1);
 }

src/yqueue.hpp

@@ -35,6 +35,7 @@
 
 #include "err.hpp"
 #include "atomic_ptr.hpp"
+#include "platform.hpp"
 
 namespace zmq
 {
@@ -50,7 +51,7 @@ namespace zmq
 //  T is the type of the object in the queue.
 //  N is granularity of the queue (how many pushes have to be done till
 //  actual memory allocation is required).
-#ifdef HAVE_POSIX_MEMALIGN
+#if defined HAVE_POSIX_MEMALIGN
 // ALIGN is the memory alignment size to use in the case where we have
 // posix_memalign available. Default value is 64, this alignment will
 // prevent two queue chunks from occupying the same CPU cache line on
@@ -181,7 +182,7 @@ template <typename T, int N> class yqueue_t
 
     static inline chunk_t *allocate_chunk ()
     {
-#ifdef HAVE_POSIX_MEMALIGN
+#if defined HAVE_POSIX_MEMALIGN
         void *pv;
         if (posix_memalign (&pv, ALIGN, sizeof (chunk_t)) == 0)
             return (chunk_t *) pv;