X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FSupport%2FIncludeFile.h;h=a9319725d4775502d3d4c1ade7be85767a7cf267;hb=5eb301740c4ee5d978535caa917cc004733a7fca;hp=2e4f12dbbf8f574bd71acce409e73243816b6bf3;hpb=6df60a9effe4d20a48cfd9d105c0ab3c5dc3e690;p=oota-llvm.git

diff --git a/include/llvm/Support/IncludeFile.h b/include/llvm/Support/IncludeFile.h
index 2e4f12dbbf8..a9319725d47 100644
--- a/include/llvm/Support/IncludeFile.h
+++ b/include/llvm/Support/IncludeFile.h
@@ -2,18 +2,60 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by Reid Spencer and is distributed under the 
-// University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines the IncludeFile class.
+// This file defines the FORCE_DEFINING_FILE_TO_BE_LINKED and DEFINE_FILE_FOR
+// macros.
 //
 //===----------------------------------------------------------------------===//
 
-/// This class is used as a facility to make sure that the implementation of a 
-/// header file is included into a tool that uses the header.  This is solely 
-/// to overcome problems linking .a files and not getting the implementation 
+#ifndef LLVM_SYSTEM_INCLUDEFILE_H
+#define LLVM_SYSTEM_INCLUDEFILE_H
+
+/// This macro is the public interface that IncludeFile.h exports. This gives
+/// us the option to implement the "link the definition" capability in any
+/// manner that we choose. All header files that depend on a specific .cpp
+/// file being linked at run time should use this macro instead of the
+/// IncludeFile class directly.
+///
+/// For example, foo.h would use:<br/>
+/// <tt>FORCE_DEFINING_FILE_TO_BE_LINKED(foo)</tt><br/>
+///
+/// And, foo.cp would use:<br/>
+/// <tt>DEFINING_FILE_FOR(foo)</tt><br/>
+#ifdef __GNUC__
+// If the `used' attribute is available, use it to create a variable
+// with an initializer that will force the linking of the defining file.
+#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
+  namespace llvm { \
+    extern const char name ## LinkVar; \
+    __attribute__((used)) static const char *const name ## LinkObj = \
+      &name ## LinkVar; \
+  }
+#else
+// Otherwise use a constructor call.
+#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
+  namespace llvm { \
+    extern const char name ## LinkVar; \
+    static const IncludeFile name ## LinkObj ( &name ## LinkVar ); \
+  }
+#endif
+
+/// This macro is the counterpart to FORCE_DEFINING_FILE_TO_BE_LINKED. It should
+/// be used in a .cpp file to define the name referenced in a header file that
+/// will cause linkage of the .cpp file. It should only be used at extern level.
+#define DEFINING_FILE_FOR(name) \
+  namespace llvm { const char name ## LinkVar = 0; }
+
+namespace llvm {
+
+/// This class is used in the implementation of FORCE_DEFINING_FILE_TO_BE_LINKED
+/// macro to make sure that the implementation of a header file is included
+/// into a tool that uses the header.  This is solely
+/// to overcome problems linking .a files and not getting the implementation
 /// of compilation units we need. This is commonly an issue with the various
 /// Passes but also occurs elsewhere in LLVM. We like to use .a files because
 /// they link faster and provide the smallest executables. However, sometimes
@@ -22,19 +64,16 @@
 /// helps to resolve that problem. The basic strategy is to use this class in
 /// a header file and pass the address of a variable to the constructor. If the
 /// variable is defined in the header file's corresponding .cpp file then all
-/// tools/libraries that #include the header file will require the .cpp as well.
+/// tools/libraries that \#include the header file will require the .cpp as
+/// well.
 /// For example:<br/>
 /// <tt>extern int LinkMyCodeStub;</tt><br/>
 /// <tt>static IncludeFile LinkMyModule(&LinkMyCodeStub);</tt><br/>
 /// @brief Class to ensure linking of corresponding object file.
-
-#ifndef LLVM_SUPPORT_INCLUDEFILE_H
-#define LLVM_SUPPORT_INCLUDEFILE_H
-
-namespace llvm {
 struct IncludeFile {
-  IncludeFile(void *);
+  explicit IncludeFile(const void *);
 };
+
 }
 
 #endif