Explicitly allow JR offsets to wrap around in RGBLINK

This reverts commit f27a813.

Author: Rangi42

src/link/patch.cpp

@@ -588,12 +588,14 @@ static void applyFilePatches(Section &section, Section &dataSection) {
 				// Offset is relative to the byte *after* the operand
 				// PC as operand to `jr` is lower than reference PC by 2
 				uint16_t address = patch.pcSection->org + patch.pcOffset + 2;
-				int32_t jumpOffset = value - address;
+				// The truncation of `value - address` is intentional, since
+				// a low ROM0 address may `jr` to a high HRAM one.
+				int16_t jumpOffset = value - address;
 
 				if (jumpOffset < -128 || jumpOffset > 127) {
 					firstErrorAt(
 					    patch,
-					    "`JR` target must be between -128 and 127 bytes away, not %" PRId32
+					    "`JR` target must be between -128 and 127 bytes away, not %" PRId16
 					    "; use `JP` instead",
 					    jumpOffset
 					);

test/link/jr-wraparound/a.asm

@@ -0,0 +1,3 @@
+SECTION "low", ROM0[$0048]
+LCDInterrupt:
+	jr hLCDInterruptHandler

test/link/jr-wraparound/b.asm

@@ -0,0 +1,4 @@
+SECTION "high", HRAM[$FFE0]
+hLCDInterruptHandler::
+.jp: db ; should be $c3 (jp)
+.address: dw

test/link/jr-wraparound/ref.out.bin

@@ -0,0 +1,5 @@
+; File generated by rgblink
+00:0048 LCDInterrupt
+00:ffe0 hLCDInterruptHandler
+00:ffe0 hLCDInterruptHandler.jp
+00:ffe1 hLCDInterruptHandler.address

test/link/jr-wraparound/ref.out.sym

@@ -191,6 +191,16 @@ tryDiff "$test"/ref.out.map "$outtemp"
 tryDiff "$test"/ref.out.sym "$outtemp2"
 evaluateTest
 
+test="jr-wraparound"
+startTest
+"$RGBASM" -o "$otemp" "$test"/a.asm
+"$RGBASM" -o "$outtemp" "$test"/b.asm
+continueTest
+rgblinkQuiet -o "$gbtemp" -n "$outtemp2" "$otemp" "$outtemp"
+tryCmpRom "$test"/ref.out.bin
+tryDiff "$test"/ref.out.sym "$outtemp2"
+evaluateTest
+
 test="high-low"
 startTest
 "$RGBASM" -o "$otemp" "$test"/a.asm