merge from dev

include/mimalloc/prim.h

@@ -209,19 +209,20 @@ static inline void mi_prim_tls_slot_set(size_t slot, void* value) mi_attr_noexce
 #elif _WIN32 && MI_WIN_USE_FIXED_TLS && !defined(MI_WIN_USE_FLS)
 
 // On windows we can store the thread-local heap at a fixed TLS slot to avoid
-// thread-local initialization checks in the fast path. This uses a fixed location
-// in the TCB though (last user-reserved slot by default) which may clash with other applications.
-
+// thread-local initialization checks in the fast path. 
+// We always use the second user TLS slot (the first one is always allocated already),
+// and at initialization (`windows/prim.c`) we call TlsAlloc and verify
+// we indeed get the second slot (and fail otherwise).
+// Todo: we could make the Tls slot completely dynamic but that would require
+// an extra read of the static Tls slot instead of using a constant offset.
 #define MI_HAS_TLS_SLOT      2              // 2 = we can reliably initialize the slot (saving a test on each malloc)
 
 #if MI_WIN_USE_FIXED_TLS > 1
 #define MI_TLS_SLOT     (MI_WIN_USE_FIXED_TLS)
 #elif MI_SIZE_SIZE == 4
-#define MI_TLS_SLOT     (0x710)             // Last user-reserved slot <https://en.wikipedia.org/wiki/Win32_Thread_Information_Block>
-// #define MI_TLS_SLOT  (0xF0C)             // Last TlsSlot (might clash with other app reserved slot)
+#define MI_TLS_SLOT     (0x0E18)            // Second User TLS slot <https://en.wikipedia.org/wiki/Win32_Thread_Information_Block>
 #else
-#define MI_TLS_SLOT     (0x888)             // Last user-reserved slot <https://en.wikipedia.org/wiki/Win32_Thread_Information_Block>
-// #define MI_TLS_SLOT  (0x1678)            // Last TlsSlot (might clash with other app reserved slot)
+#define MI_TLS_SLOT     (0x1488)            // Second User TLS slot <https://en.wikipedia.org/wiki/Win32_Thread_Information_Block>
 #endif
 
 static inline void* mi_prim_tls_slot(size_t slot) mi_attr_noexcept {

src/os.c

@@ -1,5 +1,5 @@
 /* ----------------------------------------------------------------------------
-Copyright (c) 2018-2023, Microsoft Research, Daan Leijen
+Copyright (c) 2018-2025, Microsoft Research, Daan Leijen
 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.
@@ -172,8 +172,8 @@ static void mi_os_free_huge_os_pages(void* p, size_t size);
 
 static void mi_os_prim_free(void* addr, size_t size, size_t commit_size) {
   mi_assert_internal((size % _mi_os_page_size()) == 0);
-  if (addr == NULL || size == 0) return; // || _mi_os_is_huge_reserved(addr)
-  int err = _mi_prim_free(addr, size);
+  if (addr == NULL) return; // || _mi_os_is_huge_reserved(addr)
+  int err = _mi_prim_free(addr, size);  // allow size==0 (issue #1041)
   if (err != 0) {
     _mi_warning_message("unable to free OS memory (error: %d (0x%x), size: 0x%zx bytes, address: %p)\n", err, err, size, addr);
   }

src/prim/emscripten/prim.c

@@ -1,5 +1,5 @@
 /* ----------------------------------------------------------------------------
-Copyright (c) 2018-2023, Microsoft Research, Daan Leijen, Alon Zakai
+Copyright (c) 2018-2025, Microsoft Research, Daan Leijen, Alon Zakai
 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.
@@ -58,7 +58,7 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config) {
 extern void emmalloc_free(void*);
 
 int _mi_prim_free(void* addr, size_t size) {
-  MI_UNUSED(size);
+  if (size==0) return 0;
   emmalloc_free(addr);
   return 0;
 }

src/prim/unix/prim.c

@@ -1,5 +1,5 @@
 /* ----------------------------------------------------------------------------
-Copyright (c) 2018-2023, Microsoft Research, Daan Leijen
+Copyright (c) 2018-2025, Microsoft Research, Daan Leijen
 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.
@@ -72,7 +72,6 @@ terms of the MIT license. A copy of the license can be found in the file
 
 #define MI_UNIX_LARGE_PAGE_SIZE (2*MI_MiB) // TODO: can we query the OS for this?
 
-
 //------------------------------------------------------------------------------------
 // Use syscalls for some primitives to allow for libraries that override open/read/close etc.
 // and do allocation themselves; using syscalls prevents recursion when mimalloc is
@@ -188,6 +187,7 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config )
 //---------------------------------------------
 
 int _mi_prim_free(void* addr, size_t size ) {
+  if (size==0) return 0;
   bool err = (munmap(addr, size) == -1);
   return (err ? errno : 0);
 }

src/prim/windows/prim.c

@@ -650,8 +650,20 @@ static void NTAPI mi_win_main(PVOID module, DWORD reason, LPVOID reserved) {
   MI_UNUSED(reserved);
   MI_UNUSED(module);
   #if MI_TLS_SLOT >= 2
-  if ((reason==DLL_PROCESS_ATTACH || reason==DLL_THREAD_ATTACH) && mi_prim_get_default_heap() == NULL) {
-    _mi_heap_set_default_direct((mi_heap_t*)&_mi_heap_empty);
+  if (reason==DLL_PROCESS_ATTACH) {
+    const DWORD tls_slot = TlsAlloc();
+    if (tls_slot != 1) { 
+      _mi_error_message(EFAULT, "unable to allocate the second TLS slot (rebuild without MI_WIN_USE_FIXED_TLS?)\n"); 
+    }
+  }
+  if (reason==DLL_PROCESS_ATTACH || reason==DLL_THREAD_ATTACH) {
+    if (mi_prim_get_default_heap() == NULL) {
+      _mi_heap_set_default_direct((mi_heap_t*)&_mi_heap_empty);
+    }
+    #if MI_DEBUG
+    void* const p = TlsGetValue(1);
+    mi_assert_internal(p == (void*)&_mi_heap_empty);
+    #endif  
   }
   #endif
   if (reason==DLL_PROCESS_ATTACH) {

test/main-override-dep.cpp

@@ -1,6 +1,7 @@
-// Issue #981: test overriding allocation in a DLL that is compiled independent of mimalloc. 
+// Issue #981: test overriding allocation in a DLL that is compiled independent of mimalloc.
 // This is imported by the `mimalloc-test-override` project.
 #include <string>
+#include <iostream>
 #include "main-override-dep.h"
 
 std::string TestAllocInDll::GetString()
@@ -10,6 +11,7 @@ std::string TestAllocInDll::GetString()
 	const char* t = "test";
 	memcpy(test, t, 4);
 	std::string r = test;
+  std::cout << "override-dep: GetString: " << r << "\n";
 	delete[] test;
 	return r;
 }
@@ -22,4 +24,37 @@ void TestAllocInDll::TestHeapAlloc()
 	int* p = (int*)HeapAlloc(heap, 0, sizeof(int));
 	*p = 42;
 	HeapFree(heap, 0, p);
-}
+}
+
+class Static {
+private:
+  void* p;
+public:
+  Static() {
+    printf("override-dep: static constructor\n");
+    p = malloc(64);
+    return;
+  }
+  ~Static() {
+    free(p);
+    printf("override-dep: static destructor\n");
+    return;
+  }
+};
+
+static Static s = Static();
+
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE module, DWORD reason, LPVOID reserved) {
+  (void)(reserved);
+  (void)(module);
+  if (reason==DLL_PROCESS_ATTACH) {
+    printf("override-dep: dll attach\n");
+  }
+  else if (reason==DLL_PROCESS_DETACH) {
+    printf("override-dep: dll detach\n");
+  }
+  return TRUE;
+}

test/main-override.cpp

@@ -150,7 +150,7 @@ static void test_dep()
 {
   TestAllocInDll t;
   std::string s = t.GetString();
-
+  std::cout << "test_dep GetString: " << s << "\n";
   t.TestHeapAlloc();
 }
 #endif