Layout

Determine the layout of C and C++ types, including their size, and the size, offset, and padding of each field in the type.

The layout utility uses libclang to generate a C or C++ file with calls to sizeof and offsetof that can be used with a specific compiler to understand the layout of a given type.o

Example

Suppose we have the following C++ struct defined in a file named test.cpp:

struct Type;
struct String;
struct Method;
struct Array;

struct EventInfo
{
  Type* declaringType;
  Type* reflectedType;
  String* name;
  Method* addMethod;
  Method* removeMethod;
  Method* raiseMethod;
  int eventAttributes;
  Array* otherMethods;
};

Then we can run layout like this:

$ layout test.cpp | g++ -xc++ -;./a.out
EventInfo (64b):
          Field |     Type | Offset | Size | Padding
  declaringType |   Type * |      0 |    8 |       0
  reflectedType |   Type * |      8 |    8 |       0
           name | String * |     16 |    8 |       0
      addMethod | Method * |     24 |    8 |       0
   removeMethod | Method * |     32 |    8 |       0
    raiseMethod | Method * |     40 |    8 |       0
eventAttributes |      int |     48 |    4 |       4
   otherMethods |  Array * |     56 |    8 |       0

Building

The layout utility depends on libclang. It uses CMake and Ninja to build.

Linux

$ sudo apt-get install -y llvm-9-dev libclang-9-dev cmake ninja-build
$ ./build.sh

License

This source code is licensed under the MIT License.