From 088961f77706ace3b21a73c54aa4777913198115 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Domagoj=20=C5=A0ari=C4=87?= <dsaritz@gmail.com>
Date: Thu, 29 Aug 2024 13:51:24 +0200
Subject: [PATCH] Windows:  - fixes and cleanups in anonymous mappings logic  -
 changes to handling the win32 null vs invalid handle 'logic'.

---
 include/psi/vm/handles/handle.win32.hpp  |  6 ++++-
 include/psi/vm/handles/handle_ref.hpp    |  2 +-
 include/psi/vm/vector.hpp                |  2 +-
 src/mappable_objects/file/file.win32.cpp |  7 ++++--
 src/mapped_view/mapped_view.win32.cpp    | 28 ++++++++++++++++--------
 5 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/include/psi/vm/handles/handle.win32.hpp b/include/psi/vm/handles/handle.win32.hpp
index 57adadd..f931f2b 100644
--- a/include/psi/vm/handles/handle.win32.hpp
+++ b/include/psi/vm/handles/handle.win32.hpp
@@ -34,11 +34,15 @@ struct handle_traits
 {
     using native_t = boost::winapi::HANDLE_;
 
-    inline static native_t const invalid_value{ boost::winapi::invalid_handle_value }; //...mrmlj...or nullptr eg. for CreateFileMapping
+    inline static native_t const invalid_value{ nullptr }; // Win32 is inconsistent: some parts use null while other parts use INVALID_HANDLE_VALUE
 
     static BOOST_ATTRIBUTES( BOOST_MINSIZE, BOOST_RESTRICTED_FUNCTION_L1, BOOST_EXCEPTIONLESS )
     void close( native_t const native_handle )
     {
+#   if defined( __clang__ ) || defined( __GNUC__ )
+        if ( __builtin_constant_p( native_handle ) && ( native_handle == nullptr || native_handle == boost::winapi::INVALID_HANDLE_VALUE_ ) )
+            return;
+#   endif
         BOOST_VERIFY
         (
             ( boost::winapi::CloseHandle( native_handle ) != false ) ||
diff --git a/include/psi/vm/handles/handle_ref.hpp b/include/psi/vm/handles/handle_ref.hpp
index 4dafe5d..a9e7ec1 100644
--- a/include/psi/vm/handles/handle_ref.hpp
+++ b/include/psi/vm/handles/handle_ref.hpp
@@ -50,7 +50,7 @@ struct handle_ref
 
     [[ gnu::pure ]] constexpr bool operator==( native_handle_t const other ) const noexcept { return value == other; }
 
-    native_handle_t const value;
+    native_handle_t value;
 }; // struct handle_ref
 
 #ifdef _MSC_VER
diff --git a/include/psi/vm/vector.hpp b/include/psi/vm/vector.hpp
index 2847aa9..c43b2fe 100644
--- a/include/psi/vm/vector.hpp
+++ b/include/psi/vm/vector.hpp
@@ -230,7 +230,7 @@ class contiguous_container_storage
         if constexpr ( !headerless )
         {
             auto & stored_size{ this->stored_size() };
-            BOOST_ASSERT_MSG( stored_size == 0, "Got garbage in an anonymous mapping!?" );
+            BOOST_ASSUME( stored_size == 0 ); // Got garbage in an anonymous mapping!?
             stored_size = size;
         }
         return err::success;
diff --git a/src/mappable_objects/file/file.win32.cpp b/src/mappable_objects/file/file.win32.cpp
index f54297d..27c7987 100644
--- a/src/mappable_objects/file/file.win32.cpp
+++ b/src/mappable_objects/file/file.win32.cpp
@@ -126,7 +126,7 @@ namespace detail
                     nullptr, // OBJECT_ATTRIBUTES
                     &maximum_size,
                     flags,
-                    SEC_RESERVE,
+                    SEC_COMMIT,
                     file
                 )
             };
@@ -142,8 +142,11 @@ namespace detail
         }
 
         BOOST_ATTRIBUTES( BOOST_EXCEPTIONLESS, BOOST_RESTRICTED_FUNCTION_L1 ) BOOST_FORCEINLINE
-        mapping BOOST_CC_REG do_map( file_handle::reference const file, flags::mapping const flags, std::uint64_t const maximum_size, auto const * __restrict const name ) noexcept
+        mapping BOOST_CC_REG do_map( file_handle::reference file, flags::mapping const flags, std::uint64_t const maximum_size, auto const * __restrict const name ) noexcept
         {
+            if ( file == file_handle::invalid_value )
+                file.value = INVALID_HANDLE_VALUE; // CreateFileMapping wants this instead of null
+
             ::SECURITY_ATTRIBUTES sa;
             auto const p_security_attributes( flags::detail::make_sa_ptr( sa, flags.system_access.p_sd, reinterpret_cast<bool const &>/*static_cast<bool>*/( flags.child_access ) ) );
             auto const max_sz               ( reinterpret_cast<ULARGE_INTEGER const &>( maximum_size ) );
diff --git a/src/mapped_view/mapped_view.win32.cpp b/src/mapped_view/mapped_view.win32.cpp
index 5bbac94..268e6b6 100644
--- a/src/mapped_view/mapped_view.win32.cpp
+++ b/src/mapped_view/mapped_view.win32.cpp
@@ -57,9 +57,15 @@ map
             )
         )
     };
+    return
+    {
+        view_start,
+        view_start ? desired_size : 0
+    };
 #else
+    // TODO flags parameter
     LARGE_INTEGER nt_offset{ .QuadPart = static_cast<LONGLONG>( offset ) };
-    auto sz{ desired_size };
+    auto   sz{ desired_size };
     void * view_startv{ nullptr };
     auto const success
     {
@@ -77,15 +83,19 @@ map
             PAGE_READWRITE
         )
     };
-    BOOST_ASSERT( sz >= desired_size );
-    auto const view_start{ static_cast<std::byte *>( view_startv ) };
-#endif
-
-    return
+    if ( success == nt::STATUS_SUCCESS ) [[ likely ]]
     {
-        view_start,
-        view_start ? desired_size : 0
-    };
+        BOOST_ASSUME( sz          >= desired_size );
+        BOOST_ASSUME( view_startv != nullptr      );
+        return { static_cast<std::byte *>( view_startv ), sz };
+    }
+    else
+    {
+        BOOST_ASSUME( sz          == 0       );
+        BOOST_ASSUME( view_startv == nullptr );
+        return {};
+    }
+#endif
 }
 
 namespace