POSIX: quick-fix to support anonymous/pagefile backed mappings.

psiha · Sep 16, 2024 · e9fe3d5 · e9fe3d5
1 parent 37c8fdd
commit e9fe3d5
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Showing 2 changed files with 12 additions and 2 deletions.
diff --git a/include/psi/vm/mappable_objects/file/file.posix.hpp b/include/psi/vm/mappable_objects/file/file.posix.hpp
@@ -74,7 +74,14 @@ mapping BOOST_CC_REG create_mapping
 {
     // Apple guidelines http://developer.apple.com/library/mac/#documentation/Performance/Conceptual/FileSystem/Articles/MappingFiles.html
     (void)child_access; //...mrmlj...figure out what to do with this...
-    return { std::forward<Handle>( file ), flags::viewing::create( object_access, share_mode ), size };
+    auto view_flags{ flags::viewing::create( object_access, share_mode ) };
+    if ( !file )
+    {
+        // emulate the Windows interface: null file signifies that the user
+        // wants a temporary/non-persisted 'anonymous'/pagefile-backed mapping
+        view_flags.flags |= MAP_ANONYMOUS;
+    }
+    return { std::forward<Handle>( file ), view_flags, size };
 }
 #endif // POSIX impl level
 

diff --git a/include/psi/vm/mapping/mapping.posix.hpp b/include/psi/vm/mapping/mapping.posix.hpp
@@ -59,7 +59,7 @@ struct [[ clang::trivial_abi ]] mapping
         ) == 0;
     }
 
-    bool is_file_based() const noexcept { return this->get() != posix::handle::invalid_value; }
+    bool is_file_based() const noexcept { return posix::handle::operator bool(); }
 
     posix::handle::      reference underlying_file()       noexcept { BOOST_ASSERT( is_file_based() ); return *this; }
     posix::handle::const_reference underlying_file() const noexcept { BOOST_ASSERT( is_file_based() ); return *this; }
@@ -74,6 +74,9 @@ struct [[ clang::trivial_abi ]] mapping
         return *this;
     }
 
+    // override Handle operator bool to allow for anonymous mappings
+    explicit operator bool() const noexcept { return posix::handle::operator bool() || ( view_mapping_flags.flags & MAP_ANONYMOUS ); }
+
     flags::viewing view_mapping_flags{};
     std  ::size_t  maximum_size      {};
 }; // struct mapping