diff --git a/CMakeLists.txt b/CMakeLists.txt
index a5f32884..72f83e17 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -165,7 +165,7 @@ endif()
 
 # Compiler flags
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU")
-  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden)
+  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -Wstrict-prototypes -fvisibility=hidden)
   if(CMAKE_C_COMPILER_ID MATCHES "GNU")
     list(APPEND mi_cflags -Wno-invalid-memory-model)
   endif()
diff --git a/include/mimalloc-atomic.h b/include/mimalloc-atomic.h
index dc48f0a2..e07df84d 100644
--- a/include/mimalloc-atomic.h
+++ b/include/mimalloc-atomic.h
@@ -25,7 +25,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #define  mi_memory_order(name)  std::memory_order_##name
 #elif defined(_MSC_VER)
 // Use MSVC C wrapper for C11 atomics
-#define  _Atomic(tp)            tp
+#define  _Atomic(tp)            tp 
 #define  ATOMIC_VAR_INIT(x)     x
 #define  mi_atomic(name)        mi_atomic_##name
 #define  mi_memory_order(name)  mi_memory_order_##name
@@ -173,7 +173,7 @@ static inline uintptr_t mi_atomic_exchange_explicit(_Atomic(uintptr_t)*p, uintpt
 }
 static inline void mi_atomic_thread_fence(mi_memory_order mo) {
   (void)(mo);
-  _Atomic(uintptr_t)x = 0;
+  _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) {
diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index 56efd244..bb76b4a3 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -57,7 +57,7 @@ static inline uintptr_t _mi_random_shuffle(uintptr_t x);
 extern mi_decl_cache_align mi_stats_t       _mi_stats_main;
 extern mi_decl_cache_align const mi_page_t  _mi_page_empty;
 bool       _mi_is_main_thread(void);
-bool       _mi_preloading();  // true while the C runtime is not ready
+bool       _mi_preloading(void);  // true while the C runtime is not ready
 
 // os.c
 size_t     _mi_os_page_size(void);
diff --git a/src/alloc.c b/src/alloc.c
index 2d527a57..b4af8be7 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4,6 +4,10 @@ This is free software; you can redistribute it and/or modify it under the
 terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
+#ifndef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE   // for realpath() on Linux
+#endif
+
 #include "mimalloc.h"
 #include "mimalloc-internal.h"
 #include "mimalloc-atomic.h"
@@ -465,7 +469,7 @@ static inline mi_segment_t* mi_checked_ptr_segment(const void* p, const char* ms
 #endif
 #if (MI_DEBUG>0 || MI_SECURE>=4)
   if (mi_unlikely(_mi_ptr_cookie(segment) != segment->cookie)) {
-    _mi_error_message(EINVAL, "%s: pointer does not point to a valid heap space: %p\n", p);
+    _mi_error_message(EINVAL, "%s: pointer does not point to a valid heap space: %p\n", msg, p);
   }
 #endif
   return segment;
@@ -747,7 +751,7 @@ mi_decl_restrict char* mi_heap_realpath(mi_heap_t* heap, const char* fname, char
 }
 #else
 #include <unistd.h>  // pathconf
-static size_t mi_path_max() {
+static size_t mi_path_max(void) {
   static size_t path_max = 0;
   if (path_max <= 0) {
     long m = pathconf("/",_PC_PATH_MAX);
@@ -807,13 +811,13 @@ static bool mi_try_new_handler(bool nothrow) {
   }
 }
 #else
-typedef void (*std_new_handler_t)();
+typedef void (*std_new_handler_t)(void);
 
 #if (defined(__GNUC__) || defined(__clang__))
-std_new_handler_t __attribute((weak)) _ZSt15get_new_handlerv() {
+std_new_handler_t __attribute((weak)) _ZSt15get_new_handlerv(void) {
   return NULL;
 }
-static std_new_handler_t mi_get_new_handler() {
+static std_new_handler_t mi_get_new_handler(void) {
   return _ZSt15get_new_handlerv();
 }
 #else
diff --git a/src/options.c b/src/options.c
index 055f8446..5f2eedec 100644
--- a/src/options.c
+++ b/src/options.c
@@ -22,7 +22,7 @@ terms of the MIT license. A copy of the license can be found in the file
 static uintptr_t mi_max_error_count   = 16; // stop outputting errors after this
 static uintptr_t mi_max_warning_count = 16; // stop outputting warnings after this
 
-static void mi_add_stderr_output();
+static void mi_add_stderr_output(void);
 
 int mi_version(void) mi_attr_noexcept {
   return MI_MALLOC_VERSION;
@@ -412,6 +412,14 @@ static void mi_strlcat(char* dest, const char* src, size_t dest_size) {
   dest[dest_size - 1] = 0;
 }
 
+#ifdef MI_NO_GETENV
+static bool mi_getenv(const char* name, char* result, size_t result_size) {
+  UNUSED(name);
+  UNUSED(result);
+  UNUSED(result_size);
+  return false;
+}
+#else
 static inline int mi_strnicmp(const char* s, const char* t, size_t n) {
   if (n==0) return 0;
   for (; *s != 0 && *t != 0 && n > 0; s++, t++, n--) {
@@ -419,7 +427,6 @@ static inline int mi_strnicmp(const char* s, const char* t, size_t n) {
   }
   return (n==0 ? 0 : *s - *t);
 }
-
 #if defined _WIN32
 // On Windows use GetEnvironmentVariable instead of getenv to work
 // reliably even when this is invoked before the C runtime is initialized.
@@ -487,7 +494,8 @@ static bool mi_getenv(const char* name, char* result, size_t result_size) {
     return false;
   }
 }
-#endif
+#endif  // !MI_USE_ENVIRON
+#endif  // !MI_NO_GETENV
 
 static void mi_option_init(mi_option_desc_t* desc) {  
   // Read option value from the environment
diff --git a/src/os.c b/src/os.c
index ec59f586..a79f7d7d 100644
--- a/src/os.c
+++ b/src/os.c
@@ -87,7 +87,7 @@ size_t _mi_os_page_size() {
 }
 
 // if large OS pages are supported (2 or 4MiB), then return the size, otherwise return the small page size (4KiB)
-size_t _mi_os_large_page_size() {
+size_t _mi_os_large_page_size(void) {
   return (large_os_page_size != 0 ? large_os_page_size : _mi_os_page_size());
 }
 
@@ -256,7 +256,7 @@ static void* mi_os_get_aligned_hint(size_t try_alignment, size_t size);
 
 static void* mi_win_virtual_allocx(void* addr, size_t size, size_t try_alignment, DWORD flags) {
 #if (MI_INTPTR_SIZE >= 8)
-  // on 64-bit systems, try to use the virtual address area after 4TiB for 4MiB aligned allocations
+  // on 64-bit systems, try to use the virtual address area after 2TiB for 4MiB aligned allocations
   void* hint;
   if (addr == NULL && (hint = mi_os_get_aligned_hint(try_alignment,size)) != NULL) {
     void* p = VirtualAlloc(hint, size, flags, PAGE_READWRITE);
@@ -369,7 +369,7 @@ static void* mi_wasm_heap_grow(size_t size, size_t try_alignment) {
 static void* mi_unix_mmapx(void* addr, size_t size, size_t try_alignment, int protect_flags, int flags, int fd) {
   void* p = NULL;
   #if (MI_INTPTR_SIZE >= 8) && !defined(MAP_ALIGNED)
-  // on 64-bit systems, use the virtual address area after 4TiB for 4MiB aligned allocations
+  // on 64-bit systems, use the virtual address area after 2TiB for 4MiB aligned allocations
   void* hint;
   if (addr == NULL && (hint = mi_os_get_aligned_hint(try_alignment, size)) != NULL) {
     p = mmap(hint,size,protect_flags,flags,fd,0);
@@ -506,7 +506,7 @@ static void* mi_unix_mmap(void* addr, size_t size, size_t try_alignment, int pro
 #endif
 
 // On 64-bit systems, we can do efficient aligned allocation by using
-// the 4TiB to 30TiB area to allocate them.
+// the 2TiB to 30TiB area to allocate them.
 #if (MI_INTPTR_SIZE >= 8) && (defined(_WIN32) || (defined(MI_OS_USE_MMAP) && !defined(MAP_ALIGNED)))
 static mi_decl_cache_align _Atomic(uintptr_t) aligned_base;
 
diff --git a/src/random.c b/src/random.c
index d5f75bf8..a9e4c9cc 100644
--- a/src/random.c
+++ b/src/random.c
@@ -4,6 +4,10 @@ This is free software; you can redistribute it and/or modify it under the
 terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
+#ifndef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE   // for syscall() on Linux
+#endif
+
 #include "mimalloc.h"
 #include "mimalloc-internal.h"
 
diff --git a/src/region.c b/src/region.c
index 79540730..2f68b140 100644
--- a/src/region.c
+++ b/src/region.c
@@ -40,7 +40,7 @@ Possible issues:
 #include "bitmap.h"
 
 // Internal raw OS interface
-size_t  _mi_os_large_page_size();
+size_t  _mi_os_large_page_size(void);
 bool    _mi_os_protect(void* addr, size_t size);
 bool    _mi_os_unprotect(void* addr, size_t size);
 bool    _mi_os_commit(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
diff --git a/src/stats.c b/src/stats.c
index 7ad73c84..37f65da4 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -412,10 +412,14 @@ mi_msecs_t _mi_clock_now(void) {
 }
 #else
 #include <time.h>
-#ifdef CLOCK_REALTIME
+#if defined(CLOCK_REALTIME) || defined(CLOCK_MONOTONIC)
 mi_msecs_t _mi_clock_now(void) {
   struct timespec t;
+  #ifdef CLOCK_MONOTONIC
+  clock_gettime(CLOCK_MONOTONIC, &t);
+  #else  
   clock_gettime(CLOCK_REALTIME, &t);
+  #endif
   return ((mi_msecs_t)t.tv_sec * 1000) + ((mi_msecs_t)t.tv_nsec / 1000000);
 }
 #else
diff --git a/test/test-api.c b/test/test-api.c
index d3344928..53e7f3d8 100644
--- a/test/test-api.c
+++ b/test/test-api.c
@@ -64,15 +64,15 @@ static int failed = 0;
 // ---------------------------------------------------------------------------
 // Test functions
 // ---------------------------------------------------------------------------
-bool test_heap1();
-bool test_heap2();
-bool test_stl_allocator1();
-bool test_stl_allocator2();
+bool test_heap1(void);
+bool test_heap2(void);
+bool test_stl_allocator1(void);
+bool test_stl_allocator2(void);
 
 // ---------------------------------------------------------------------------
 // Main testing
 // ---------------------------------------------------------------------------
-int main() {
+int main(void) {
   mi_option_disable(mi_option_verbose);
 
   // ---------------------------------------------------