cast const ptr: remove some unneeded code

- remove some unneeded paramaters
- tidy up changelog.txt

This commit is the end point in a series of changes since revision 145c13f.
This series of commits relates to errors and warnings on usafe CONST usage with respect to CONST qualifiers, assignments, argument passing, conversions, casting, and overloaded functions (both user and built-in)
	In general:
		1) some unsafe CONST usages are now errors
		2) many unsage CONST usages are reported when using '-w constness' compiler warning option

#642 Pointer casting allows constness dropping
	Unsafe statements not reporting any warning or error.  The fix probably occurred over several revisions due to several related bugs.  Revision numbers below are approximate.

	In revision approx 7185995, a warning is generated for this unsafe usage but only when '-w constness' warning is specified.  Internal implementation was modified in the source revisions following.

	```
	#pragma constness=true
	dim as const integer a = 256
	*cast( integer ptr, @A ) = 257 '' unsafe, warning with -w constness
	poke integer, @A, 257          '' unsafe, warning with -w constness
	```

	In revision 2960949 for bug fix #727, adds CONST qualifiers to prototypes for fb rtlib built-in functions.  We get an error due the incompatible and unsafe CONSTs.
	```
	dim as const integer a = 256
	clear a, 0, sizeof(integer)    '' unsafe, error
	print a '' 0
	```

	Consider this bug report fixed.  Promoting warnings to errors, specifically with CAST, CPTR, STRPTR, etc should be considered a different issue and a new bug ticket.

#886 Inconsistent error with BYREF and CAST on CONST variables
	Fixed approx revision 612162a and on going implementation changes in the following revisions.  Fixed by preserving the conversions, even CONST only conversions in the AST tree.  For some expressions, there is no symbol associated, so AST needs to preserve the CONSTness of an expression so that it can be correctly type checked later.

#801 parser allows more constructs under -exx than without it
	Fixed at revision 391527e.  Requires bug fix #886, and adds and additional code to solve out null pointer where not needed.

#880 Overload binary operators do not support covariant arguments
	Fixed at revision 208fad4.  Maybe "changed" is better descriptor.  Needs more testing.

#727 RTL functions not checking Constness unless marked RTL_CONST
	All built-in RTL functions now have CONST added, where CONST is applicable.
	Even though 'BYVAL' and 'BYVAL as CONST' are identical, and the compiler disregards any difference between the two, BYVAL parameters also carry the CONST attribute.  The reason is that BYVAL/BYREF conveys one kind of information and CONST/non-CONST conveys another, and there is no harm (that I know of) to be more explicit.

Author: jayrm

changelog.txt

@@ -5,6 +5,8 @@ Version 1.06.0
 - test-suite uses libfbcunit for unit testing framework
 - SELECT CASE AS CONST respects data type and will show overflow warnings on out-of-range constants
 - boolean: don't allow NEG unary op '-' on boolean data types
+- All fb RTL functions are checked for CONSTness, CONST qualifiers added to fb rtlib built-in prototypes (sf.net #727)
+- WSTRING can be a return type, but only for prototypes (DECLARE) and function pointers, this allows getting PROCPTR() of all fb built-in run time functions
 
 [added]
 - -noobjinfo option to disable the writing/reading of compile-time library and other linking options from/to .o and .a files. This also disables the use of fbextra.x (the supplemental linker script) for discarding the .fbctinf sections, which is useful when using the gold linker that doesn't support this kind of linker script.
@@ -15,7 +17,8 @@ Version 1.06.0
 - Updated bindings: SDL2 2.0.6, SDL2_image 2.0.1, SDL2_mixer 2.0.1, SDL2_net 2.0.1, SDL2_ttf 2.0.14
 - allow overload operator SQR()
 - allow [static] shared byref variables to be initialized with byref variable
-- warning '-w constness' to enable 'CONST qualifier discarded' warning
+- warning '-w constness' to enable 'CONST qualifier discarded' warning on command line
+- #pragma constness to enable/disable 'CONST qualifier discarded' warning in source code
 
 [fixed]
 - win/d3dx9.bi no longer has a hard-coded #inclib "d3dx9d". d3dx9d.dll is apparently not a generally valid choice. In practice programs have to be linked against d3dx9_33.dll or d3dx9_39.dll, etc.
@@ -68,6 +71,7 @@ Version 1.06.0
 - #884: FORMATing dates can deadlock under Unix
 - #642, #886: CASTs involving CONST qualifiers solved out too early allowing invalid statements to be compiled
 - #801: *@(expr) solved to (expr) did not cleanly remove null ptr checks allowing invalid datatype assignment with -exx.  *PTRCHK(@expr) solves to (expr).
+- #880: Overload binary operators now support covariant arguments, overloaded procedure resolution changed especially with respect to CONST and non-CONST parameters
 
 
 Version 1.05.0

src/compiler/ast-node-conv.bas

@@ -488,22 +488,10 @@ function astNewCONV _
 	'' Discarding/changing const qualifier bits ?
 	if( typeIsPtr( ldtype ) and typeIsPtr( to_dtype ) ) then
 
-		errmsg = 0
 		wrnmsg = 0
 
-		n->cast.convconst = ( symbCheckConstAssign( to_dtype, ldtype, to_subtype, l->subtype, , , errmsg, wrnmsg ) = FALSE )
+		n->cast.convconst = ( symbCheckConstAssign( to_dtype, ldtype, to_subtype, l->subtype, , , wrnmsg ) = FALSE )
 
-		'' error message takes priority over warning messages
-		if( (options and AST_CONVOPT_DONTCHKPTR) = 0 ) then
-			if( errmsg <> FB_ERRMSG_OK ) then
-				if( perrmsg ) then
-					*perrmsg = errmsg
-				end if
-				astDelTree( n )
-				exit function
-			end if
-		end if
-		
 		'' else check if const conversion
 		if( n->cast.convconst ) then
 			if( (options and AST_CONVOPT_DONTWARNCONST) = 0 ) then

src/compiler/symb.bas

@@ -1877,9 +1877,7 @@ function symbCheckConstAssignTopLevel _
 		byval lsubtype as FBSYMBOL ptr, _
 		byval rsubtype as FBSYMBOL ptr, _
 		byval mode as FB_PARAMMODE = 0, _
-		byref matches as integer = 0, _
-		byref errmsg as FB_ERRMSG = 0, _
-		byref wrnmsg as FB_WARNINGMSG = 0 _
+		byref matches as integer = 0 _
 	) as integer
 
 	dim as integer i = any, lcount = any, rcount = any, rmatches = any
@@ -1979,15 +1977,14 @@ function symbCheckConstAssignTopLevel _
 	function = TRUE
 end function
 
-function hSymbCheckConstAssignFuncPtr _
+private function hSymbCheckConstAssignFuncPtr _
 	( _
 		byval ldtype as FB_DATATYPE, _
 		byval rdtype as FB_DATATYPE, _
 		byval lsubtype as FBSYMBOL ptr, _
 		byval rsubtype as FBSYMBOL ptr, _
 		byval mode as FB_PARAMMODE = 0, _
 		byref matches as integer = 0, _
-		byref errmsg as FB_ERRMSG = 0, _
 		byref wrnmsg as FB_WARNINGMSG = 0 _
 	) as integer
 
@@ -1997,6 +1994,10 @@ function hSymbCheckConstAssignFuncPtr _
 
 	function = FALSE
 
+	'' TODO
+	'' 1) consider also combining (in some way) with symbCalcProcMatch()
+	'' 2) the structure of the call is very similar
+	'' 3) possibly leading towards a generic type compatibility check
 
 	assert( typeGetDtOnly( ldType ) = FB_DATATYPE_FUNCTION )
 	assert( typeGetDtOnly( rdType ) = FB_DATATYPE_FUNCTION )
@@ -2053,7 +2054,7 @@ function hSymbCheckConstAssignFuncPtr _
 		var ls = symbGetSubType( rparam )
 		var m = symbGetParamMode( lparam )
 
-		if( symbCheckConstAssign( l, r, ls, rs, m, , errmsg, wrnmsg ) = FALSE ) then
+		if( symbCheckConstAssign( l, r, ls, rs, m, , wrnmsg ) = FALSE ) then
 			exit function
 		end if
 
@@ -2072,22 +2073,28 @@ function symbCheckConstAssign _
 		byval rsubtype as FBSYMBOL ptr, _
 		byval mode as FB_PARAMMODE = 0, _
 		byref matches as integer = 0, _
-		byref errmsg as FB_ERRMSG = 0, _
 		byref wrnmsg as FB_WARNINGMSG = 0 _
 	) as integer
 
+	'' TODO:
+	'' 1) consider combining 
+	''      - symbCheckConstAssign()
+	''      - hSymbCheckConstAssignFuncPtr()
+	''      - symbCheckConstAssignTopLevel()
+	'' 2) callers of symbCheckConstAssignTopLevel() need to respond to errors 
+	''    and warnings if calling symbCheckConstAssign() instead
+
 	dim ret as integer = any
 
-	errmsg = FB_ERRMSG_OK '' FB_ERRMSG
 	wrnmsg = 0            '' FB_WARNINGMSG
 
 	'' check top-level const
-	ret = symbCheckConstAssignTopLevel( ldtype, rdtype, lsubtype, rsubtype, mode, matches, errmsg, wrnmsg )
+	ret = symbCheckConstAssignTopLevel( ldtype, rdtype, lsubtype, rsubtype, mode, matches )
 
 	if( ret ) then
 		'' both types function pointer?
 		if( ( typeGetDtOnly( ldType ) = FB_DATATYPE_FUNCTION ) and ( typeGetDtOnly( rdType ) = FB_DATATYPE_FUNCTION ) ) then
-			ret and= hSymbCheckConstAssignFuncPtr( ldtype, rdtype, lsubtype, rsubtype, mode, matches, errmsg, wrnmsg )
+			ret and= hSymbCheckConstAssignFuncPtr( ldtype, rdtype, lsubtype, rsubtype, mode, matches, wrnmsg )
 		end if
 	end if
 

src/compiler/symb.bi

@@ -1878,9 +1878,7 @@ declare function symbCheckConstAssignTopLevel _
 		byval lsubtype as FBSYMBOL ptr, _
 		byval rsubtype as FBSYMBOL ptr, _
 		byval mode as FB_PARAMMODE = 0, _
-		byref matches as integer = 0, _
-		byref errmsg as FB_ERRMSG = 0, _
-		byref wrnmsg as FB_WARNINGMSG = 0 _
+		byref matches as integer = 0 _
 	) as integer
 
 declare function symbCheckConstAssign _
@@ -1891,7 +1889,6 @@ declare function symbCheckConstAssign _
 		byval rsubtype as FBSYMBOL ptr, _
 		byval mode as FB_PARAMMODE = 0, _
 		byref matches as integer = 0, _
-		byref errmsg as FB_ERRMSG = 0, _
 		byref wrnmsg as FB_WARNINGMSG = 0 _
 	) as integer