[build] Really fix multi and C++ builds.

The following builds were still failing due to previous changes:

  make multi
  make multi CC="c++"
  make CC="c++"

This patch fixes the issues, which were missing includes to get the
right macro definitions in multi-build mode.

Also, `FT_UNUSED' is actually used by third-party code, so move it
back to `public-macros.h' to avoid breaking it.

* include/freetype/config/public-macros.h (FT_EXPORT): Remove
special definition for C++.
(FT_UNUSED): Define here instead of...
* include/freetype/config/compiler-macros.h: ... here.
(FT_FUNCTION_DECLARATION): Remove special definition for C++.
(FT_LOCAL_ARRAY_DEF): Fix definition.

* src/cache/ftccback.h, src/lzw/ftzopen.h, src/gxvalid/gxvmort.h,
src/gxvalid/gxvmorx.h: Add `FT_BEGIN_HEADER' and `FT_END_HEADER'.

7 files changed, 58 insertions, 18 deletions

diff --git a/ChangeLog b/ChangeLog
index 7bf83a028..39d2e8915 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,29 @@
+2020-07-07  David Turner  <david@freetype.org>
+
+	[build] Really fix multi and C++ builds.
+
+	The following builds were still failing due to previous changes:
+
+	  make multi
+	  make multi CC="c++"
+	  make CC="c++"
+
+	This patch fixes the issues, which were missing includes to get the
+	right macro definitions in multi-build mode.
+
+	Also, `FT_UNUSED' is actually used by third-party code, so move it
+	back to `public-macros.h' to avoid breaking it.
+
+	* include/freetype/config/public-macros.h (FT_EXPORT): Remove
+	special definition for C++.
+	(FT_UNUSED): Define here instead of...
+	* include/freetype/config/compiler-macros.h: ... here.
+	(FT_FUNCTION_DECLARATION): Remove special definition for C++.
+	(FT_LOCAL_ARRAY_DEF): Fix definition.
+
+	* src/cache/ftccback.h, src/lzw/ftzopen.h, src/gxvalid/gxvmort.h,
+	src/gxvalid/gxvmorx.h: Add `FT_BEGIN_HEADER' and `FT_END_HEADER'.
+
 2020-07-06  David Turner  <david@freetype.org>
 
 	[build] Fix multi and C++ builds.
diff --git a/include/freetype/config/public-macros.h b/include/freetype/config/public-macros.h
index b1fa0f2b3..5cc3236ed 100644
--- a/include/freetype/config/public-macros.h
+++ b/include/freetype/config/public-macros.h
@@ -78,13 +78,23 @@ FT_BEGIN_HEADER
  *
  *     FT_EXPORT( FT_Bool )  FT_Object_Method( FT_Object obj, ... );
  *
+ * NOTE: This requires that all FT_EXPORT() uses are inside FT_BEGIN_HEADER ..
+ * FT_END_HEADER blocks. This guarantees that the functions are exported with
+ * C linkage, even when the header is included by a C++ source file.
  */
-#ifdef __cplusplus
-#define FT_EXPORT( x )  FT_PUBLIC_FUNCTION_ATTRIBUTE extern "C" x
-#else
 #define FT_EXPORT( x )  FT_PUBLIC_FUNCTION_ATTRIBUTE extern x
+
+  /* `FT_UNUSED` indicates that a given parameter is not used --   */
+  /* this is only used to get rid of unpleasant compiler warnings. */
+  /*                                                               */
+  /* Technically, this was not meant to be part of the public API, */
+  /* but some third-party code depends on it.                      */
+  /*                                                               */
+#ifndef FT_UNUSED
+#define FT_UNUSED( arg )  ( (arg) = (arg) )
 #endif
 
+
 FT_END_HEADER
 
 #endif  /* FREETYPE_CONFIG_PUBLIC_MACROS_H_ */
diff --git a/include/freetype/internal/compiler-macros.h b/include/freetype/internal/compiler-macros.h
index 1f432bca5..b62c0777b 100644
--- a/include/freetype/internal/compiler-macros.h
+++ b/include/freetype/internal/compiler-macros.h
@@ -29,12 +29,6 @@ FT_BEGIN_HEADER
 #  endif
 #endif
 
-  /* `FT_UNUSED` indicates that a given parameter is not used --   */
-  /* this is only used to get rid of unpleasant compiler warnings. */
-#ifndef FT_UNUSED
-#define FT_UNUSED( arg )  ( (arg) = (arg) )
-#endif
-
   /* Fix compiler warning with sgi compiler. */
 #if defined( __sgi ) && !defined( __GNUC__ )
 #  if defined( _COMPILER_VERSION ) && ( _COMPILER_VERSION >= 730 )
@@ -126,18 +120,13 @@ FT_BEGIN_HEADER
  *
  *    FT_FUNCTION_DECLARATION(int) foo(int x);
  *
- * NOTE: Technically, all FreeType headers put their function declarations
- * inside an extern "C" block, giving them C linkage. This means that using
- * this macro is only necessary within internal source files, but using it in
- * a header will be harmless.
+ * NOTE: This requires that all uses are inside FT_BEGIN_HEADER..FT_END_HEADER
+ * blocks. Which guarantees that the declarations have C linkage when the
+ * headers are included by C++ sources.
  *
  * NOTE: Do not use directly, use FT_LOCAL()/FT_BASE()/FT_EXPORT() instead.
  */
-#ifdef __cplusplus
-#define FT_FUNCTION_DECLARATION( x )  extern "C" x
-#else
 #define FT_FUNCTION_DECLARATION( x )  extern x
-#endif
 
 /* Same as FT_FUNCTION_DECLARATION(), but for function definitions instead.
  * NOTE: Do not use directly, use FT_LOCAL_DEF()/FT_BASE_DEF()/FT_EXPORT_DEF()
@@ -171,7 +160,7 @@ FT_BEGIN_HEADER
  * sub-directory, but are otherwise internal to the library.
  */
 #define FT_LOCAL_ARRAY( x )      FT_INTERNAL_FUNCTION_ATTRIBUTE extern const x
-#define FT_LOCAL_ARRAY_DEF( x )  const x
+#define FT_LOCAL_ARRAY_DEF( x )  FT_FUNCTION_DEFINITION( const x )
 
 /* Use FT_BASE()/FT_BASE_DEF() to declare or define an internal library
  * function that are used by more than one single module.
diff --git a/src/cache/ftccback.h b/src/cache/ftccback.h
index 802fd4444..542acb156 100644
--- a/src/cache/ftccback.h
+++ b/src/cache/ftccback.h
@@ -25,6 +25,7 @@
 #include "ftcglyph.h"
 #include "ftcsbits.h"
 
+FT_BEGIN_HEADER
 
   FT_LOCAL( void )
   ftc_inode_free( FTC_Node   inode,
@@ -84,6 +85,7 @@
   ftc_node_destroy( FTC_Node     node,
                     FTC_Manager  manager );
 
+FT_END_HEADER
 
 #endif /* FTCCBACK_H_ */
 
diff --git a/src/gxvalid/gxvmort.h b/src/gxvalid/gxvmort.h
index 24c7e45b2..7237c5825 100644
--- a/src/gxvalid/gxvmort.h
+++ b/src/gxvalid/gxvmort.h
@@ -34,6 +34,9 @@
 #include <freetype/ftsnames.h>
 
 
+FT_BEGIN_HEADER
+
+
   typedef struct  GXV_mort_featureRec_
   {
     FT_UShort  featureType;
@@ -88,6 +91,8 @@
                                     GXV_Validator  gxvalid );
 
 
+FT_END_HEADER
+
 #endif /* GXVMORT_H_ */
 
 
diff --git a/src/gxvalid/gxvmorx.h b/src/gxvalid/gxvmorx.h
index ceb14a9e8..f747b1d63 100644
--- a/src/gxvalid/gxvmorx.h
+++ b/src/gxvalid/gxvmorx.h
@@ -36,6 +36,9 @@
 #include <freetype/ftsnames.h>
 
 
+FT_BEGIN_HEADER
+
+
   FT_LOCAL( void )
   gxv_morx_subtable_type0_validate( FT_Bytes       table,
                                     FT_Bytes       limit,
@@ -62,6 +65,8 @@
                                     GXV_Validator  gxvalid );
 
 
+FT_END_HEADER
+
 #endif /* GXVMORX_H_ */
 
 
diff --git a/src/lzw/ftzopen.h b/src/lzw/ftzopen.h
index cb9206b3e..d8768f7b4 100644
--- a/src/lzw/ftzopen.h
+++ b/src/lzw/ftzopen.h
@@ -24,6 +24,7 @@
 
 #include <freetype/freetype.h>
 
+FT_BEGIN_HEADER
 
   /*
    * This is a complete re-implementation of the LZW file reader,
@@ -165,6 +166,8 @@
 
 /* */
 
+FT_END_HEADER
+
 #endif /* FTZOPEN_H_ */