diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index ecdcf860..73aa236c 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -22,7 +22,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #define mi_decl_noinline        __declspec(noinline)
 #define mi_decl_thread          __declspec(thread)
 #define mi_decl_cache_align     __declspec(align(MI_CACHE_LINE))
-#elif (defined(__GNUC__) && (__GNUC__>=3))  // includes clang and icc
+#elif (defined(__GNUC__) && (__GNUC__ >= 3)) || defined(__clang__) // includes clang and icc
 #define mi_decl_noinline        __attribute__((noinline))
 #define mi_decl_thread          __thread
 #define mi_decl_cache_align     __attribute__((aligned(MI_CACHE_LINE)))
@@ -240,7 +240,7 @@ static inline bool mi_malloc_satisfies_alignment(size_t alignment, size_t size)
 }
 
 // Overflow detecting multiply
-#if __has_builtin(__builtin_umul_overflow) || __GNUC__ >= 5
+#if __has_builtin(__builtin_umul_overflow) || (defined(__GNUC__) && (__GNUC__ >= 5))
 #include <limits.h>      // UINT_MAX, ULONG_MAX
 #if defined(_CLOCK_T)    // for Illumos
 #undef _CLOCK_T
@@ -907,7 +907,7 @@ static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
 // This is used for example in `mi_realloc`.
 // -------------------------------------------------------------------------------
 
-#if (__GNUC__ >= 4) || defined(__clang__)
+#if (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)
 // On GCC/CLang we provide a hint that the pointers are word aligned.
 #include <string.h>
 static inline void _mi_memcpy_aligned(void* dst, const void* src, size_t n) {
diff --git a/include/mimalloc.h b/include/mimalloc.h
index fe5aa8f3..7ebf3e60 100644
--- a/include/mimalloc.h
+++ b/include/mimalloc.h
@@ -26,7 +26,7 @@ terms of the MIT license. A copy of the license can be found in the file
 
 #if defined(__cplusplus) && (__cplusplus >= 201703)
   #define mi_decl_nodiscard    [[nodiscard]]
-#elif (__GNUC__ >= 4) || defined(__clang__)  // includes clang, icc, and clang-cl
+#elif (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)  // includes clang, icc, and clang-cl
   #define mi_decl_nodiscard    __attribute__((warn_unused_result))
 #elif (_MSC_VER >= 1700)
   #define mi_decl_nodiscard    _Check_return_
diff --git a/test/main-override.cpp b/test/main-override.cpp
index 5fe3f9a3..e1795ecb 100644
--- a/test/main-override.cpp
+++ b/test/main-override.cpp
@@ -26,14 +26,15 @@ static void msleep(unsigned long msecs) { Sleep(msecs); }
 static void msleep(unsigned long msecs) { usleep(msecs * 1000UL); }
 #endif
 
-void heap_thread_free_large(); // issue #221
-void heap_no_delete();         // issue #202
-void heap_late_free();         // issue #204
-void padding_shrink();         // issue #209
-void various_tests();
-void test_mt_shutdown();
-void fail_aslr();              // issue #372
-void tsan_numa_test();         // issue #414
+static void heap_thread_free_large(); // issue #221
+static void heap_no_delete();         // issue #202
+static void heap_late_free();         // issue #204
+static void padding_shrink();         // issue #209
+static void various_tests();
+static void test_mt_shutdown();
+static void fail_aslr();              // issue #372
+static void tsan_numa_test();         // issue #414
+static void strdup_test();     // issue #445
 
 int main() {
   mi_stats_reset();  // ignore earlier allocations
@@ -43,6 +44,7 @@ int main() {
   padding_shrink();
   various_tests();
   tsan_numa_test();
+  strdup_test();
 
   //test_mt_shutdown();
   //fail_aslr();
@@ -66,7 +68,7 @@ public:
 };
 
 
-void various_tests() {
+static void various_tests() {
   atexit(free_p);
   void* p1 = malloc(78);
   void* p2 = mi_malloc_aligned(16, 24);
@@ -74,18 +76,13 @@ void various_tests() {
   p1 = malloc(8);
   char* s = mi_strdup("hello\n");
 
-  //char* s = _strdup("hello\n");
-  //char* buf = NULL;
-  //size_t len;
-  //_dupenv_s(&buf,&len,"MIMALLOC_VERBOSE"); 
-  //mi_free(buf);
-
   mi_free(p2);
   p2 = malloc(16);
   p1 = realloc(p1, 32);
   free(p1);
   free(p2);
   mi_free(s);
+
   Test* t = new Test(42);
   delete t;
   t = new (std::nothrow) Test(42);
@@ -109,7 +106,7 @@ public:
 static Static s = Static();
 
 
-bool test_stl_allocator1() {
+static bool test_stl_allocator1() {
   std::vector<int, mi_stl_allocator<int> > vec;
   vec.push_back(1);
   vec.pop_back();
@@ -118,38 +115,48 @@ bool test_stl_allocator1() {
 
 struct some_struct { int i; int j; double z; };
 
-bool test_stl_allocator2() {
+static bool test_stl_allocator2() {
   std::vector<some_struct, mi_stl_allocator<some_struct> > vec;
   vec.push_back(some_struct());
   vec.pop_back();
   return vec.size() == 0;
 }
 
-
+// issue 445
+static void strdup_test() {
+#ifdef _MSC_VER
+  char* s = _strdup("hello\n");
+  char* buf = NULL;
+  size_t len;
+  _dupenv_s(&buf, &len, "MIMALLOC_VERBOSE");
+  mi_free(buf);
+  mi_free(s);
+#endif
+}
 
 // Issue #202
-void heap_no_delete_worker() {
+static void heap_no_delete_worker() {
   mi_heap_t* heap = mi_heap_new();
   void* q = mi_heap_malloc(heap, 1024);
   // mi_heap_delete(heap); // uncomment to prevent assertion
 }
 
-void heap_no_delete() {
+static void heap_no_delete() {
   auto t1 = std::thread(heap_no_delete_worker);
   t1.join();
 }
 
 
 // Issue #204
-volatile void* global_p;
+static volatile void* global_p;
 
-void t1main() {
+static void t1main() {
   mi_heap_t* heap = mi_heap_new();
   global_p = mi_heap_malloc(heap, 1024);
   mi_heap_delete(heap);
 }
 
-void heap_late_free() {
+static void heap_late_free() {
   auto t1 = std::thread(t1main);
 
   msleep(2000);
@@ -166,7 +173,7 @@ static void alloc0(/* void* arg */)
   shared_p = mi_malloc(8);
 }
 
-void padding_shrink(void)
+static void padding_shrink(void)
 {
   auto t1 = std::thread(alloc0);
   t1.join();
@@ -175,11 +182,11 @@ void padding_shrink(void)
 
 
 // Issue #221
-void heap_thread_free_large_worker() {
+static void heap_thread_free_large_worker() {
   mi_free(shared_p);
 }
 
-void heap_thread_free_large() {
+static void heap_thread_free_large() {
   for (int i = 0; i < 100; i++) {
     shared_p = mi_malloc_aligned(2*1024*1024 + 1, 8);
     auto t1 = std::thread(heap_thread_free_large_worker);
@@ -189,7 +196,7 @@ void heap_thread_free_large() {
 
 
 
-void test_mt_shutdown()
+static void test_mt_shutdown()
 {
   const int threads = 5;
   std::vector< std::future< std::vector< char* > > > ts;
@@ -214,7 +221,7 @@ void test_mt_shutdown()
 }
 
 // issue #372
-void fail_aslr() {
+static void fail_aslr() {
   size_t sz = (4ULL << 40); // 4TiB
   void* p = malloc(sz);
   printf("pointer p: %p: area up to %p\n", p, (uint8_t*)p + sz);
@@ -222,12 +229,12 @@ void fail_aslr() {
 }
 
 // issues #414
-void dummy_worker() {
+static void dummy_worker() {
   void* p = mi_malloc(0);
   mi_free(p);  
 }
 
-void tsan_numa_test() {
+static void tsan_numa_test() {
   auto t1 = std::thread(dummy_worker);
   dummy_worker();
   t1.join();