fbc: add '-z nobuiltins' command line option

- '-z nobuiltins' command line option disables all built-in procedure
  definitions except for those that are required by current version.
- procedures fb_Init(), fb_InitSignals(), __main(), fb_end(), _monstartup()
  are required since they are referenced by rtlAppInit() and rtlExitApp()
  and currently this generated code can not be disabled.
- internal: added FB_RTL_OPT_REQUIRED to indicate required procedures
- other procedures are still required for fbc to compile user code fully,
  but it depends on the user code to be compiled.  Therefore it is
  possible to provide declarations and definitions for the of the other
  built-in procedures needed in the user source code itself if the
  declaration is made before it is actually referenced by the compiler
  and defined before linking the executable

changelog.txt

@@ -38,6 +38,7 @@ Version 1.20.0
 - fbc: __FB_BUILD_FORK_ID__ intrinsic define.  By default is an empty string.  Can be customized by makefile
 - fbc: '-print fork-id' command line option to report the fork-id version of fbc
 - fbc: '-nolib fbrt0.o' and '-nolib fbrt0pic.o' can be used to omit fb's startup files from the link.  Implied by '-nodeflibs'.
+- fbc: '-z nobuiltins' command line option to disable all non-required built-in procedure definitions
 
 [fixed]
 - github #410: give consistent floating point comparisons results involving NaNs.

doc/fbc.1

@@ -285,6 +285,9 @@ Don't use '__fastcall' calling convention
 \fB\-z no-thiscall\fR
 Don't use '__thiscall' calling convention
 .TP
+\fB\-z nobuiltins\fR
+Disable all non-required builtin procedure definitions
+.TP
 \fB\-z nocmdline\fR
 Disable #cmdline source directives
 .TP

src/compiler/fb.bas

@@ -603,6 +603,7 @@ sub fbGlobalInit()
 	env.clopt.modeview      = FB_DEFAULT_MODEVIEW
 	env.clopt.nocmdline     = FALSE
 	env.clopt.returninflts  = FALSE
+	env.clopt.nobuiltins    = FALSE
 
 	env.restart_request     = FB_RESTART_NONE
 	env.restart_action      = FB_RESTART_NONE
@@ -738,6 +739,8 @@ sub fbSetOption( byval opt as integer, byval value as integer )
 	case FB_COMPOPT_RETURNINFLTS
 		env.clopt.returninflts = value
 		hUpdateTargetOptions( )
+	case FB_COMPOPT_NOBUILTINS
+		env.clopt.nobuiltins = value
 	end select
 end sub
 
@@ -836,6 +839,8 @@ function fbGetOption( byval opt as integer ) as integer
 		function = env.clopt.nocmdline
 	case FB_COMPOPT_RETURNINFLTS
 		function = env.clopt.returninflts
+	case FB_COMPOPT_NOBUILTINS
+		function = env.clopt.nobuiltins
 
 	case else
 		function = 0

src/compiler/fb.bi

@@ -118,6 +118,7 @@ enum FB_COMPOPT
 	FB_COMPOPT_MODEVIEW             '' enum: FB_MODEVIEW (__FB_GUI__)
 	FB_COMPOPT_NOCMDLINE            '' boolean: -z nocmdline, disable #cmdline directives
 	FB_COMPOPT_RETURNINFLTS         '' boolean: -z retinflts, enable returning some structs in floating point registers
+	FB_COMPOPT_NOBUILTINS           '' boolean: -z nobuiltins, disable all non-required builtin procedure definitions
 
 	FB_COMPOPTIONS
 end enum
@@ -333,6 +334,7 @@ type FBCMMLINEOPT
 	modeview        as FB_MODEVIEW
 	nocmdline       as integer              '' dissallow #cmdline directive? (default = false)
 	returninflts    as integer              '' enable returning some structs in floating point registers
+	nobuiltins      as integer              '' disable all non-required builtin procedure definitions
 end type
 
 '' features allowed in the selected language

src/compiler/fbc.bas

@@ -2510,6 +2510,8 @@ private sub handleOpt _
 			fbSetOption( FB_COMPOPT_NOCMDLINE, TRUE )
 		case "retinflts"
 			fbSetOption( FB_COMPOPT_RETURNINFLTS, TRUE )
+		case "nobuiltins"
+			fbSetOption( FB_COMPOPT_NOBUILTINS, TRUE )
 		case else
 			hFatalInvalidOption( arg, is_source )
 		end select
@@ -4520,6 +4522,7 @@ private sub hPrintOptions( byval verbose as integer )
 	print "  -z gosub-setjmp  Use setjmp/longjmp to implement GOSUB"
 	print "  -z no-thiscall   Don't use '__thiscall' calling convention"
 	print "  -z no-fastcall   Don't use '__fastcall' calling convention"
+	print "  -z nobuiltins    Disable all non-required builtin procedure definitions"
 	print "  -z nocmdline     Disable #cmdline source directives"
 	print "  -z retinflts     Enable returning some types in floating point registers"
 	print "  -z valist-as-ptr Use pointer expressions to implement CVA_*() macros"

src/compiler/rtl-profile.bas

@@ -41,7 +41,7 @@
 		( _
 			@FB_RTL_PROFILEMONSTARTUP, @"_monstartup", _
 			FB_DATATYPE_VOID, FB_FUNCMODE_CDECL, _
-			NULL, FB_RTL_OPT_NONE, _
+			NULL, FB_RTL_OPT_REQUIRED, _
 			0 _
 		), _
 		( NULL ) _

src/compiler/rtl-system.bas

@@ -24,7 +24,7 @@ declare function    hThreadCall_cb      ( byval sym as FBSYMBOL ptr ) as integer
 		( _
 			@FB_RTL_INIT, NULL, _
 			FB_DATATYPE_VOID, FB_FUNCMODE_FBCALL, _
-			NULL, FB_RTL_OPT_NONE, _
+			NULL, FB_RTL_OPT_REQUIRED, _
 			3, _
 			{ _
 				( FB_DATATYPE_LONG, FB_PARAMMODE_BYVAL, FALSE ), _
@@ -36,21 +36,21 @@ declare function    hThreadCall_cb      ( byval sym as FBSYMBOL ptr ) as integer
 		( _
 			@FB_RTL_INITSIGNALS, NULL, _
 			FB_DATATYPE_VOID, FB_FUNCMODE_FBCALL, _
-			NULL, FB_RTL_OPT_NONE, _
+			NULL, FB_RTL_OPT_REQUIRED, _
 			0 _
 		), _
 		/' sub __main cdecl( ) '/ _
 		( _
 			@FB_RTL_INITCRTCTOR, @"__main", _
 			FB_DATATYPE_VOID, FB_FUNCMODE_CDECL, _
-			NULL, FB_RTL_OPT_NONE, _
+			NULL, FB_RTL_OPT_REQUIRED, _
 			0 _
 		), _
 		/' sub fb_End( byval errlevel as const long ) '/ _
 		( _
 			@FB_RTL_END, NULL, _
 			FB_DATATYPE_VOID, FB_FUNCMODE_FBCALL, _
-			NULL, FB_RTL_OPT_NONE, _
+			NULL, FB_RTL_OPT_REQUIRED, _
 			1, _
 			{ _
 				( typeSetIsConst( FB_DATATYPE_LONG ), FB_PARAMMODE_BYVAL, FALSE ) _
@@ -660,14 +660,17 @@ function rtlInitApp _
 	is_exe = (env.clopt.outtype <> FB_OUTTYPE_DYNAMICLIB)
 
 	if( env.clopt.backend = FB_BACKEND_GAS ) then
-		'' call __monstartup() on win32/cygwin if profiling
-		select case( env.clopt.target )
-		case FB_COMPTARGET_WIN32, FB_COMPTARGET_CYGWIN
-			if( env.clopt.profile ) then
-				'' __monstartup()
-				rtlProfileCall_monstartup( )
-			end if
-		end select
+
+		if( env.clopt.nobuiltins = FALSE ) then
+			'' call __monstartup() on win32/cygwin if profiling
+			select case( env.clopt.target )
+			case FB_COMPTARGET_WIN32, FB_COMPTARGET_CYGWIN
+				if( env.clopt.profile ) then
+					'' __monstartup()
+					rtlProfileCall_monstartup( )
+				end if
+			end select
+		end if
 
 		'' call default CRT0 constructors (only required for Win32)
 		if( env.clopt.target = FB_COMPTARGET_WIN32 ) then
@@ -683,15 +686,17 @@ function rtlInitApp _
 	astNewARG( proc, astNewCONSTi( env.clopt.lang ) )
 	astAdd( proc )
 
-	'' Error checking enabled and not a DLL? And emscripten doesn't have signals
-	if( env.clopt.errorcheck andalso is_exe andalso ( env.clopt.target <> FB_COMPTARGET_JS ) ) then
-		'' fb_InitSignals( )
-		astAdd( astNewCALL( PROCLOOKUP( INITSIGNALS ), NULL ) )
+	if( env.clopt.nobuiltins = FALSE ) then
+		'' Error checking enabled and not a DLL? And emscripten doesn't have signals
+		if( env.clopt.errorcheck andalso is_exe andalso ( env.clopt.target <> FB_COMPTARGET_JS ) ) then
+			'' fb_InitSignals( )
+			astAdd( astNewCALL( PROCLOOKUP( INITSIGNALS ), NULL ) )
 
-		'' Checking the CPU for features on x86
-		if( fbGetCpuFamily( ) = FB_CPUFAMILY_X86 ) then
-			'' Check CPU type
-			rtlX86CpuCheck( )
+			'' Checking the CPU for features on x86
+			if( fbGetCpuFamily( ) = FB_CPUFAMILY_X86 ) then
+				'' Check CPU type
+				rtlX86CpuCheck( )
+			end if
 		end if
 	end if
 

src/compiler/rtl.bas

@@ -138,6 +138,12 @@ sub rtlAddIntrinsicProcs( byval procdef as const FB_RTL_PROCDEF ptr )
 			end if
 		end if
 
+		if( (procdef->options and FB_RTL_OPT_REQUIRED) = 0 ) then
+			if( env.clopt.nobuiltins ) then
+				doadd = FALSE
+			end if
+		end if
+
 		if( doadd ) then
 			dim as FBSYMBOL ptr proc = symbPreAddProc( NULL )
 
@@ -255,9 +261,14 @@ sub rtlAddIntrinsicProcs( byval procdef as const FB_RTL_PROCDEF ptr )
 				palias = pname
 			end if
 
+			dim symb_opts as FB_SYMBOPT = FB_SYMBOPT_NONE
+			if( env.clopt.nobuiltins = FALSE ) then
+				symb_opts or= FB_SYMBOPT_DECLARING or FB_SYMBOPT_RTL
+			end if
+
 			proc = symbAddProc( proc, pname, palias, _
 			                    procdef->dtype, NULL, attrib, pattrib, callconv, _
-			                    FB_SYMBOPT_DECLARING or FB_SYMBOPT_RTL )
+			                    symb_opts )
 
 			if( proc <> NULL ) then
 				symbSetProcCallback( proc, procdef->callback )

src/compiler/rtl.bi

@@ -833,7 +833,7 @@ enum FB_RTL_OPT
 	FB_RTL_OPT_MT             = &h00000004  '' needs the multithreaded rtlib
 
 	FB_RTL_OPT_ASSERTONLY     = &h00000010  '' only if asserts are enabled
-	''                        = &h00000020
+	FB_RTL_OPT_REQUIRED       = &h00000020  '' required even if -z nobuiltins was given
 	FB_RTL_OPT_STRSUFFIX      = &h00000040  '' has a $ suffix (-lang qb only)
 	FB_RTL_OPT_NOQB           = &h00000080  '' anything but -lang qb
 	FB_RTL_OPT_QBONLY         = &h00000100  '' -lang qb only