1 //===- llvm/System/IncludeFile.h - Ensure Linking Of Library ---*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Reid Spencer and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the FORCE_DEFINING_FILE_TO_BE_LINKED and DEFINE_FILE_FOR
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_SYSTEM_INCLUDEFILE_H
16 #define LLVM_SYSTEM_INCLUDEFILE_H
18 /// This macro is the public interface that IncludeFile.h exports. This gives
19 /// us the option to implement the "link the definition" capability in any
20 /// manner that we choose. All header files that depend on a specific .cpp
21 /// file being linked at run time should use this macro instead of the
22 /// IncludeFile class directly.
24 /// For example, foo.h would use:<br/>
25 /// <tt>FORCE_DEFINING_FILE_TO_BE_LINKED(foo)</tt><br/>
27 /// And, foo.cp would use:<br/>
28 /// <tt>DEFINING_FILE_FOR(foo)</tt><br/>
29 #define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
31 extern char name ## LinkVar; \
32 static IncludeFile name ## LinkObj ( &name ## LinkVar ); \
35 /// This macro is the counterpart to FORCE_DEFINING_FILE_TO_BE_LINKED. It should
36 /// be used in a .cpp file to define the name referenced in a header file that
37 /// will cause linkage of the .cpp file. It should only be used at extern level.
38 #define DEFINING_FILE_FOR(name) namespace llvm { char name ## LinkVar; }
42 /// This class is used in the implementation of FORCE_DEFINING_FILE_TO_BE_LINKED
43 /// macro to make sure that the implementation of a header file is included
44 /// into a tool that uses the header. This is solely
45 /// to overcome problems linking .a files and not getting the implementation
46 /// of compilation units we need. This is commonly an issue with the various
47 /// Passes but also occurs elsewhere in LLVM. We like to use .a files because
48 /// they link faster and provide the smallest executables. However, sometimes
49 /// those executables are too small, if the program doesn't reference something
50 /// that might be needed, especially by a loaded share object. This little class
51 /// helps to resolve that problem. The basic strategy is to use this class in
52 /// a header file and pass the address of a variable to the constructor. If the
53 /// variable is defined in the header file's corresponding .cpp file then all
54 /// tools/libraries that #include the header file will require the .cpp as well.
56 /// <tt>extern int LinkMyCodeStub;</tt><br/>
57 /// <tt>static IncludeFile LinkMyModule(&LinkMyCodeStub);</tt><br/>
58 /// @brief Class to ensure linking of corresponding object file.