Description: Allow unregisterised ghc-8.2 to build newer GHC
 Commit b68697e579d38ca29c2b84377dc2affa04659a28 introduced a regression
 stopping existing unregisteristed compilers from being used to compile a newer
 version of GHC. The problem is that the bootstrap compiler uses the newer Stg.h
 where EB_, IB_, etc, definitions have changed resulting in the following error:
.
  error: conflicting types for 'ghc_GhcPrelude_zdtrModule4_bytes'
  note: in definition of macro 'EB_'
  #define EB_(X)    extern const char X[]
  note: previous definition of 'ghc_GhcPrelude_zdtrModule4_bytes' was here
  char ghc_GhcPrelude_zdtrModule4_bytes[] = "ghc";
.
 For more information about the problem, see https://phabricator.haskell.org/D4114.
.
 This patch is a rework of https://phabricator.haskell.org/D3741.
 It modifies Stg.h to include the old definitions, if a compiler older than
 8.4 is being used.
.
 This patch can be removed, once ghc-8.2 is no longer the bootstrap compiler.
Author: Ilias Tsitsimpis <iliastsi@debian.org>
Bug: https://ghc.haskell.org/trac/ghc/ticket/15201

Index: b/includes/Stg.h
===================================================================
--- a/includes/Stg.h
+++ b/includes/Stg.h
@@ -232,6 +232,16 @@ typedef StgInt    I_;
 typedef StgWord StgWordArray[];
 typedef StgFunPtr       F_;
 
+#if __GLASGOW_HASKELL__ < 804
+#define EB_(X)    extern char X[]
+#define IB_(X)    static char X[]
+#define EI_(X)          extern StgWordArray (X) GNU_ATTRIBUTE(aligned (8))
+#define II_(X)          static StgWordArray (X) GNU_ATTRIBUTE(aligned (8))
+#define IF_(f)    static StgFunPtr GNUC3_ATTRIBUTE(used) f(void)
+#define FN_(f)    StgFunPtr f(void)
+#define EF_(f)    StgFunPtr f(void) /* External Cmm functions */
+#define EFF_(f)   void f() /* See Note [External function prototypes] */
+#else
 /* byte arrays (and strings): */
 #define EB_(X)    extern const char X[]
 #define IB_(X)    static const char X[]
@@ -250,6 +260,7 @@ typedef StgFunPtr       F_;
 #define EF_(f)           StgFunPtr f(void) /* External Cmm functions */
 /* foreign functions: */
 #define EFF_(f)   void f() /* See Note [External function prototypes] */
+#endif  /* __GLASGOW_HASKELL__ < 804 */
 
 /* Note [External function prototypes]  See Trac #8965, #11395
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~