ia16-elf-gcc: remove need for far function wrappers

docs/build.txt

@@ -41,7 +41,7 @@ Linux 16.04 LTS (Xenial Xerus) or Ubuntu Linux 14.04 LTS (Trusty
 Tahr), there are precompiled ia16-elf-gcc packages at
 https://launchpad.net/~tkchia/+archive/ubuntu/build-ia16/.
 Otherwise, for now ia16-elf-gcc needs to be compiled from source.
-Only releases 20180419 and later are supported.
+Only releases 20180708 and later are supported.
 
 Notes:
 ======

hdr/portab.h

@@ -337,7 +337,11 @@ typedef signed long LONG;
 #define FP_SEG(fp)            ((unsigned)((ULONG)(VOID FAR *)(fp)>>16))
 #endif
 
+#if defined(__GNUC__) && defined(__BUILTIN_IA16_FP_OFF)
+#define FP_OFF(fp)            __builtin_ia16_FP_OFF(fp)
+#else
 #define FP_OFF(fp)            ((unsigned)(fp))
+#endif
 
 #endif
 #endif

kernel/kernel.asm

@@ -938,18 +938,6 @@ global %1lshrsi3
                 ; reserve space for far jump to cp/m routine
                 times 5 db 0
 
-%ifdef gcc
-blk_driver_wrap:mov ax, _blk_driver
-                jmp short blkclk
-clk_driver_wrap:mov ax, _clk_driver
-blkclk:         pop si
-                pop di
-                call ax
-                push di
-                push si
-                retf
-%endif
-
 ;End of HMA segment                
 segment HMA_TEXT_END
                 global  __HMATextEnd
@@ -1042,21 +1030,13 @@ _cpm_entry:     jmp 0:reloc_call_cpm_entry
                 global  _reloc_call_blk_driver
                 extern  _blk_driver
 _reloc_call_blk_driver:
-%ifdef gcc
-                jmp 0:blk_driver_wrap
-%else
                 jmp 0:_blk_driver
-%endif
                 call near forceEnableA20
 
                 global  _reloc_call_clk_driver
                 extern  _clk_driver
 _reloc_call_clk_driver:
-%ifdef gcc
-                jmp 0:clk_driver_wrap
-%else
                 jmp 0:_clk_driver
-%endif
                 call near forceEnableA20
 
                 global  _CharMapSrvc ; in _DATA (see AARD)

mkfiles/gcc.mak

@@ -54,8 +54,9 @@ CFLAGSC=
 # -Wno-pointer-to-int-cast  do not warn about FP_OFF
 # -Wno-pragmas  do not warn about #pragma pack
 # -Werror       treat all warnings as errors
+# -mfar-function-if-far-return-type treat `int __far f ();' as a far function
 
-ALLCFLAGS+=-I../hdr $(TARGETOPT) -mcmodel=small -fleading-underscore -fno-common -fpack-struct -ffreestanding -fcall-used-es -mrtd -Wno-pointer-to-int-cast -Wno-pragmas -Werror -Os -fno-strict-aliasing
+ALLCFLAGS+=-I../hdr $(TARGETOPT) -mcmodel=small -fleading-underscore -fno-common -fpack-struct -ffreestanding -fcall-used-es -mrtd -Wno-pointer-to-int-cast -Wno-pragmas -Werror -Os -fno-strict-aliasing -mfar-function-if-far-return-type
 INITCFLAGS=$(ALLCFLAGS) -o $@
 CFLAGS=$(ALLCFLAGS) -o $@