parser: Select Case As Const: Fix potential hang and overflow

A huge range like <case 0 to 4294967295u> correctly triggers an error,
but fbc still looped through all the values during error recovery, which
makes it look like it hangs.

Furthermore, I suspect the For loop could have run into overflow and
infinite looping issues, due to the iterator being a UInteger...

changelog.txt

@@ -119,6 +119,7 @@ Version 1.04.0
 - GET# didn't work with wstrings
 - Integer-only operations like AND, OR, \ and MOD converted non-integer operands to Integer, even if the other was a LongInt or UInteger. Now the conversion will use an integer type matching the integer operand (if any), to avoid truncating floating point values, and give more expected results.
 - ASM backend: Cross-compiling could give different results than native compilation with regards to the choice of whether to place string literals into .data or const (e.g. .rodata) sections
+- Compiling a Select Case As Const block containing a Case with a huge range of values such as <case 0 to 4294967295u> won't cause the compiler to "hang" anymore
 
 
 Version 1.03.0

src/compiler/parser-compound-select-const.bas

@@ -225,7 +225,8 @@ sub cSelConstStmtNext( byval stk as FB_CMPSTMTSTK ptr )
 			tovalue = value
 		end if
 
-		for value = value to tovalue
+		'' Add Case values in range unless it was something invalid like "1 to 0"
+		while( value <= tovalue )
 			if( value < minval ) then
 				minval = value
 			end if
@@ -236,15 +237,23 @@ sub cSelConstStmtNext( byval stk as FB_CMPSTMTSTK ptr )
 			'' too big?
 			if( (minval > maxval) or ((maxval - minval + 1) > FB_MAXJUMPTBSLOTS) ) then
 				errReport( FB_ERRMSG_RANGETOOLARGE )
-				'' error recovery: reset values
+				'' error recovery: reset values and abort,
+				'' to avoid excessive looping in case of code like "0 to 4294967295u"
 				minval = stk->select.const_.minval
 				maxval = stk->select.const_.maxval
-			else
-				if( hSelConstAddCase( swtbase, value, label ) = FALSE ) then
-					errReport( FB_ERRMSG_DUPDEFINITION )
-				end if
+				exit while
 			end if
-		next
+
+			if( hSelConstAddCase( swtbase, value, label ) = FALSE ) then
+				errReport( FB_ERRMSG_DUPDEFINITION )
+			end if
+
+			'' "Early" exit check to avoid overflow problems
+			if( value = tovalue ) then
+				exit while
+			end if
+			value += 1
+		wend
 
 		stk->select.const_.minval = minval
 		stk->select.const_.maxval = maxval

tests/compound/select-const-huge-range.bas

@@ -0,0 +1,5 @@
+' TEST_MODE : COMPILE_ONLY_FAIL
+
+select case as const 0
+case 0 to 4294967295u
+end select