Because a “fixed buffer” is not a real array. It is a custom value type, about the only way to generate one in the C# language that I know. There is no way for the CLR to verify that indexing of the array is done in a safe way. The code is not verifiable either. … Read more
As already mentioned by Conrad, there are some situations where unsafe access to memory in C# is useful. There are not as many of them, but there are some: Manipulating with Bitmap is almost a typical example where you need some additional performance that you can get by using unsafe. Interoperability with older API (such … Read more
It’s useful for interop with unmanaged code. Any pointers passed to unmanaged functions need to be fixed (aka. pinned) to prevent the garbage collector from relocating the underlying memory. If you are using P/Invoke, then the default marshaller will pin objects for you. Sometimes it’s necessary to perform custom marshalling, and sometimes it’s necessary to … Read more
I am not sure if you need unsafe code in that case (see answer of @mybirthname). But when unsafe code is needed, it can be enabled in Project properties. In the main menu, click Project and then <ProjectName> properties… Click on the Build page. Select Allow unsafe code. Or one can specify /unsafe compiler option … Read more
You can get the object index with Unsafe. Depending on how the JVM is using the memory (32-bit addresses, 32-bit index, 32-bit index with offset, 64-bit address) can affect how useful the object index is. Here is a program which assumes you have 32-bit index in a 64-bit JVM. import sun.misc.Unsafe; import java.lang.reflect.Field; import java.util.Arrays; … Read more
Dereference the value: fn unbox<T>(value: Box<T>) -> T { *value } There’s a nightly associated function into_inner you can use as well: #![feature(box_into_inner)] fn unbox<T>(value: Box<T>) -> T { Box::into_inner(value) } Way back in pre-1.0 Rust, heap-allocated values were very special types, and they used the sigil ~ (as in ~T). Along the road to … Read more
On .NET a float is represented using an IEEE binary32 single precision floating number stored using 32 bits. Apparently the code constructs this number by assembling the bits into an int and then casts it to a float using unsafe. The cast is what in C++ terms is called a reinterpret_cast where no conversion is … Read more
From “The Man” himself: The use of pointers is rarely required in C#, but there are some situations that require them. As examples, using an unsafe context to allow pointers is warranted by the following cases: Dealing with existing structures on disk Advanced COM or Platform Invoke scenarios that involve structures with pointers in them … Read more
Summary CPU cores have special memory ordering buffers to assist them with out-of-order execution. These can be (and typically are) separate for loading and storing: LOBs for load-order buffers and SOBs for store-order buffers. The fencing operations chosen for the Unsafe API are were selected based on the following assumption: underlying processors will have separate … Read more
In Visual Studio 2012 Express Edition: Right-click on your project -> Properties -> Configuration Properties -> Linker -> Advanced and changed “Image Has Safe Exception Handlers” to “No (/SAFESEH:NO)”