overload: Allow passing constant 0 Byte/Short to pointer params

This makes the behaviour of normal and overloaded calls match.
ast-node-conv allows assigning a literal zero integer to a pointer even if
the integer type's size didn't match the pointer size. hCalcTypesDiff() on
the other hand had a check only allowing this if the type size matched.

To fix this, the non-ptr-to-ptr checking code from ast-node-conv.bas is
extracted into a helper function which is now called by hCalcTypesDiff(),
replacing the bogus size check. This should ensure that both overload
resolution and normal cast/conv checks will behave the same (as far as
passing literal zeroes to pointers is concerned).

This also fixes the issue where it was no longer possible to call Bsave
in -lang qb with 0 as the 2nd parameter (which is a pointer), since commit
07d6977 in FB 0.90 which turned Bsave() into an overloaded function.

Author: dkl

changelog.txt

@@ -59,6 +59,7 @@ Version 1.01.0
 - PRINT now disallows commas/newlines after SPC/TAB, instead of silently ignoring them
 - 0.90.0 regression: Compiler crash during error recovery for expressions like 'type<UDT>().field' where initializer values are missing
 - When passing a constant zero of some integer to an overloaded procedure, overloads with integer parameters will now be preferred over overloads with pointers (literal 0 can still be passed to pointer parameters in this case though, by casting it to the pointer type)
+- Literal zeroes with [U]Byte or [U]Short type (or the 16bit Integer in -lang qb) can now be passed to pointer parameters of overloaded procedures (now it's possible to call Bsave() with 0 source buffer in -lang qb again -- it also was affected by this bug since FB 0.90)
 
 
 Version 1.00.0 (former 0.91.0):

src/compiler/ast-node-conv.bas

@@ -104,6 +104,41 @@ private function hGetTypeMismatchErrMsg( byval options as AST_CONVOPT ) as integ
 	end if
 end function
 
+function astCheckConvNonPtrToPtr _
+	( _
+		byval to_dtype as integer, _
+		byval expr_dtype as integer, _
+		byval expr as ASTNODE ptr, _
+		byval options as AST_CONVOPT _
+	) as integer
+
+	assert( typeIsPtr( to_dtype ) )
+	assert( typeIsPtr( expr_dtype ) = FALSE )
+
+	select case as const typeGet( expr_dtype )
+	case FB_DATATYPE_INTEGER, FB_DATATYPE_UINT, FB_DATATYPE_ENUM, _
+	     FB_DATATYPE_LONG, FB_DATATYPE_ULONG, _
+	     FB_DATATYPE_LONGINT, FB_DATATYPE_ULONGINT
+		'' Allow integer-to-pointer casts if same size
+		if( typeGetSize( expr_dtype ) = env.pointersize ) then
+			return FB_ERRMSG_OK
+		end if
+
+	'' only allow other int dtypes if it's 0 (due QB's INTEGER = short)
+	case FB_DATATYPE_BYTE, FB_DATATYPE_UBYTE, _
+	     FB_DATATYPE_SHORT, FB_DATATYPE_USHORT
+		if( astIsCONST( expr ) ) then
+			if( astConstEqZero( expr ) ) then
+				'' Allow 0-to-pointer casts
+				return FB_ERRMSG_OK
+			end if
+		end if
+
+	end select
+
+	function = hGetTypeMismatchErrMsg( options )
+end function
+
 private function hCheckPtr _
 	( _
 		byval to_dtype as integer, _
@@ -117,35 +152,11 @@ private function hCheckPtr _
 
 	'' to pointer? only allow integers of same size, and pointers
 	if( typeIsPtr( to_dtype ) ) then
-		select case as const typeGet( expr_dtype )
-		case FB_DATATYPE_INTEGER, FB_DATATYPE_UINT, FB_DATATYPE_ENUM, _
-		     FB_DATATYPE_LONG, FB_DATATYPE_ULONG, _
-		     FB_DATATYPE_LONGINT, FB_DATATYPE_ULONGINT
-			'' Allow integer-to-pointer casts if same size
-			if( typeGetSize( expr_dtype ) = env.pointersize ) then
-				exit function
-			end if
-			return hGetTypeMismatchErrMsg( options )
-
-		'' only allow other int dtypes if it's 0 (due QB's INTEGER = short)
-		case FB_DATATYPE_BYTE, FB_DATATYPE_UBYTE, _
-		     FB_DATATYPE_SHORT, FB_DATATYPE_USHORT
-			if( astIsCONST( expr ) ) then
-				if( astConstEqZero( expr ) ) then
-					'' Allow 0-to-pointer casts
-					exit function
-				end if
-			end if
-
-			return hGetTypeMismatchErrMsg( options )
-
-		case FB_DATATYPE_POINTER
-			'' Both are pointers, fall through to checks below
+		if( typeIsPtr( expr_dtype ) = FALSE ) then
+			return astCheckConvNonPtrToPtr( to_dtype, expr_dtype, expr, options )
+		end if
 
-		case else
-			'' Nothing else allowed (strings, structs)
-			return hGetTypeMismatchErrMsg( options )
-		end select
+		'' Both are pointers, fall through to checks below
 
 	'' from pointer? only allow integers of same size and pointers
 	elseif( typeIsPtr( expr_dtype ) ) then

src/compiler/ast.bi

@@ -900,6 +900,14 @@ declare function astCheckASSIGNToType _
 		byval r as ASTNODE ptr _
 	) as integer
 
+declare function astCheckConvNonPtrToPtr _
+	( _
+		byval to_dtype as integer, _
+		byval expr_dtype as integer, _
+		byval expr as ASTNODE ptr, _
+		byval options as AST_CONVOPT _
+	) as integer
+
 declare function astCheckCONV _
 	( _
 		byval to_dtype as integer, _

src/compiler/symb-proc.bas

@@ -1703,18 +1703,8 @@ private function hCalcTypesDiff _
 						return 0
 					end if
 
-					'' not a numeric constant?
-					if( astIsCONST( arg_expr ) = FALSE ) then
-						return 0
-					end if
-
-					'' not 0 (NULL)?
-					if( astConstEqZero( arg_expr ) = FALSE ) then
-						return 0
-					end if
-
-					'' not native pointer width?
-					if( typeGetSize( arg_dtype ) <> env.pointersize ) then
+					'' Allow passing literal 0 (with some non-ptr integer type) to the ptr
+					if( astCheckConvNonPtrToPtr( param_dtype, arg_dtype, arg_expr, 0 ) <> FB_ERRMSG_OK ) then
 						return 0
 					end if
 

tests/gfx/bsave-nullptr-fb.bas

@@ -0,0 +1,2 @@
+' TEST_MODE : COMPILE_ONLY_OK
+bsave("foo.bmp", 0)

tests/gfx/bsave-nullptr-qb.bas

@@ -0,0 +1,3 @@
+' TEST_MODE : COMPILE_ONLY_OK
+#lang "qb"
+bsave("foo.bmp", 0)

tests/overload/pointers.bas

@@ -816,6 +816,7 @@ namespace const0
 	private sub test cdecl( )
 		a( cptr( any ptr, 0 ) )
 		a( 0 )
+		a( 0u )
 		a( cint( 0 ) )
 		a( cuint( 0 ) )
 		#ifdef __FB_64BIT__
@@ -829,6 +830,10 @@ namespace const0
 			a( clng( 0 ) )
 			a( culng( 0 ) )
 		#endif
+		a( cbyte( 0 ) )
+		a( cubyte( 0 ) )
+		a( cshort( 0 ) )
+		a( cushort( 0 ) )
 
 		#macro makeTest1( suffix, result )
 			CU_ASSERT( f1_##suffix( cptr( any ptr, 0 ) ) = "any ptr" )