fix msvc compilation in C mode

ide/vs2017/mimalloc.vcxproj

@@ -257,4 +257,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>

include/mimalloc-atomic.h

@@ -131,18 +131,23 @@ typedef enum mi_memory_order_e {
 } mi_memory_order;
 
 static inline uintptr_t mi_atomic_fetch_add_explicit(_Atomic(uintptr_t)* p, uintptr_t add, mi_memory_order mo) {
+  (void)(mo);
   return (uintptr_t)MI_64(_InterlockedExchangeAdd)((volatile msc_intptr_t*)p, (msc_intptr_t)add);
 }
 static inline uintptr_t mi_atomic_fetch_sub_explicit(_Atomic(uintptr_t)*p, uintptr_t sub, mi_memory_order mo) {
+  (void)(mo);
   return (uintptr_t)MI_64(_InterlockedExchangeAdd)((volatile msc_intptr_t*)p, -((msc_intptr_t)sub));
 }
 static inline uintptr_t mi_atomic_fetch_and_explicit(_Atomic(uintptr_t)* p, uintptr_t x, mi_memory_order mo) {
+  (void)(mo);
   return (uintptr_t)MI_64(_InterlockedAnd)((volatile msc_intptr_t*)p, (msc_intptr_t)x);
 }
 static inline uintptr_t mi_atomic_fetch_or_explicit(_Atomic(uintptr_t)* p, uintptr_t x, mi_memory_order mo) {
+  (void)(mo);
   return (uintptr_t)MI_64(_InterlockedOr)((volatile msc_intptr_t*)p, (msc_intptr_t)x);
 }
 static inline bool mi_atomic_compare_exchange_strong_explicit(_Atomic(uintptr_t)* p, uintptr_t* expected, uintptr_t desired, mi_memory_order mo1, mi_memory_order mo2) {
+  (void)(mo1); (void)(mo2);
   uintptr_t read = (uintptr_t)MI_64(_InterlockedCompareExchange)((volatile msc_intptr_t*)p, (msc_intptr_t)desired, (msc_intptr_t)(*expected));
   if (read == *expected) {
     return true;
@@ -156,13 +161,16 @@ static inline bool mi_atomic_compare_exchange_weak_explicit(_Atomic(uintptr_t)*p
   return mi_atomic_compare_exchange_strong_explicit(p, expected, desired, mo1, mo2);
 }
 static inline uintptr_t mi_atomic_exchange_explicit(_Atomic(uintptr_t)* p, uintptr_t exchange, mi_memory_order mo) {
+  (void)(mo);
   return (uintptr_t)MI_64(_InterlockedExchange)((volatile msc_intptr_t*)p, (msc_intptr_t)exchange);
 }
-static inline mi_atomic_thread_fence(mi_memory_order mo) {
+static inline void mi_atomic_thread_fence(mi_memory_order mo) {
+  (void)(mo);
   _Atomic(uintptr_t)x = 0;
   mi_atomic_exchange_explicit(&x, 1, mo);
 }
 static inline uintptr_t mi_atomic_load_explicit(_Atomic(uintptr_t) const* p, mi_memory_order mo) {
+  (void)(mo);
   #if defined(_M_IX86) || defined(_M_X64)
   return *p;
   #else
@@ -174,6 +182,7 @@ static inline uintptr_t mi_atomic_load_explicit(_Atomic(uintptr_t) const* p, mi_
   #endif
 }
 static inline void mi_atomic_store_explicit(_Atomic(uintptr_t)* p, uintptr_t x, mi_memory_order mo) {
+  (void)(mo);
   #if defined(_M_IX86) || defined(_M_X64)
   *p = x;
   #else

include/mimalloc-types.h

@@ -12,6 +12,10 @@ terms of the MIT license. A copy of the license can be found in the file
 #include <stdint.h>   // uintptr_t, uint16_t, etc
 #include <mimalloc-atomic.h>  // _Atomic
 
+#ifdef _MSC_VER
+#pragma warning(disable:4214) // bitfield is not int
+#endif 
+
 // Minimal alignment necessary. On most platforms 16 bytes are needed
 // due to SSE registers for example. This must be at least `MI_INTPTR_SIZE`
 #ifndef MI_MAX_ALIGN_SIZE

src/heap.c

@@ -550,6 +550,9 @@ static bool mi_heap_area_visitor(const mi_heap_t* heap, const mi_heap_area_ex_t*
 
 // Visit all blocks in a heap
 bool mi_heap_visit_blocks(const mi_heap_t* heap, bool visit_blocks, mi_block_visit_fun* visitor, void* arg) {
-  mi_visit_blocks_args_t args = { visit_blocks, visitor, arg };
+  mi_visit_blocks_args_t args = { 0 };
+  args.visit_blocks = visit_blocks;
+  args.visitor = visitor;
+  args.arg = arg;
   return mi_heap_visit_areas(heap, &mi_heap_area_visitor, &args);
 }