List -B in rgbgfx options

man/rgbgfx.1

@@ -13,6 +13,7 @@
 .Op Fl CmhOuVwXYZ
 .Op Fl v Op Fl v No ...
 .Op Fl a Ar attrmap | Fl A
+.Op Fl B Ar color
 .Op Fl b Ar base_ids
 .Op Fl c Ar pal_spec
 .Op Fl \-color Ar when

src/link/section.cpp

@@ -25,7 +25,12 @@ void sect_ForEach(void (*callback)(Section &)) {
 	}
 }
 
-static void checkAgainstFixedAddress(Section const &target, Section const &other, uint16_t org) {
+static void checkPieceCompat(Section &target, Section const &other, size_t delta) {
+	assume(other.modifier != SECTION_UNION || delta == 0);
+
+	if (other.isAddressFixed) {
+		uint16_t org = other.org - delta;
+
 		if (target.isAddressFixed) {
 			if (target.org != org) {
 				fatalTwoAt(
@@ -52,9 +57,12 @@ static void checkAgainstFixedAddress(Section const &target, Section const &other
 				);
 			}
 		}
-}
 
-static bool checkAgainstFixedAlign(Section const &target, Section const &other, uint32_t ofs) {
+		target.isAddressFixed = true;
+		target.org = org;
+	} else if (other.isAlignFixed) {
+		uint32_t ofs = (other.alignOfs - delta) & other.alignMask;
+
 		if (target.isAddressFixed) {
 			if ((target.org - ofs) & other.alignMask) {
 				fatalTwoAt(
@@ -68,7 +76,6 @@ static bool checkAgainstFixedAlign(Section const &target, Section const &other,
 				    other.alignOfs
 				);
 			}
-		return false;
 		} else if (target.isAlignFixed
 		           && (other.alignMask & target.alignOfs) != (target.alignMask & ofs)) {
 			fatalTwoAt(
@@ -82,33 +89,7 @@ static bool checkAgainstFixedAlign(Section const &target, Section const &other,
 			    other.alignMask + 1,
 			    other.alignOfs
 			);
-	} else {
-		return !target.isAlignFixed || (other.alignMask > target.alignMask);
-	}
-}
-
-static void checkSectUnionCompat(Section &target, Section &other) {
-	if (other.isAddressFixed) {
-		checkAgainstFixedAddress(target, other, other.org);
-		target.isAddressFixed = true;
-		target.org = other.org;
-	} else if (other.isAlignFixed) {
-		if (checkAgainstFixedAlign(target, other, other.alignOfs)) {
-			target.isAlignFixed = true;
-			target.alignMask = other.alignMask;
-		}
-	}
-}
-
-static void checkFragmentCompat(Section &target, Section &other) {
-	if (other.isAddressFixed) {
-		uint16_t org = other.org - target.size;
-		checkAgainstFixedAddress(target, other, org);
-		target.isAddressFixed = true;
-		target.org = org;
-	} else if (other.isAlignFixed) {
-		uint32_t ofs = (other.alignOfs - target.size) & other.alignMask;
-		if (checkAgainstFixedAlign(target, other, ofs)) {
+		} else if (!target.isAlignFixed || other.alignMask > target.alignMask) {
 			target.isAlignFixed = true;
 			target.alignMask = other.alignMask;
 			target.alignOfs = ofs;
@@ -157,14 +138,14 @@ static void mergeSections(Section &target, std::unique_ptr<Section> &&other) {
 
 	switch (other->modifier) {
 	case SECTION_UNION:
-		checkSectUnionCompat(target, *other);
+		checkPieceCompat(target, *other, 0);
 		if (other->size > target.size) {
 			target.size = other->size;
 		}
 		break;
 
 	case SECTION_FRAGMENT:
-		checkFragmentCompat(target, *other);
+		checkPieceCompat(target, *other, target.size);
 		// Append `other` to `target`
 		other->offset = target.size;
 		target.size += other->size;

test/link/section-union/compat/a.asm

@@ -0,0 +1,4 @@
+SECTION "ROM", ROM0
+LOAD UNION "U", WRAM0
+        ds 1
+ENDL

test/link/section-union/compat/b.asm

@@ -0,0 +1,17 @@
+SECTION "R1", WRAM0
+        ds $77
+
+SECTION "R2", WRAM0
+        ds $ef
+
+SECTION UNION "U", WRAM0
+        ds $52e
+
+SECTION UNION "U", WRAM0
+wStart::
+        ds $89
+        assert @ & $FF == 0, "wContent must be 8-bit aligned"
+        align 8
+wContent::
+        ds $111
+wEnd::

test/link/section-union/compat/script.link

@@ -0,0 +1,5 @@
+WRAM0
+        align 8
+        "R1"
+        "U"
+        "R2"

test/link/test.sh

@@ -390,6 +390,15 @@ rgblinkQuiet "$otemp" "$gbtemp" 2>"$outtemp"
 tryDiff "$test"/out.err "$outtemp"
 evaluateTest
 
+test="section-union/compat"
+startTest
+"$RGBASM" -o "$otemp" "$test"/a.asm
+"$RGBASM" -o "$gbtemp2" "$test"/b.asm
+continueTest
+rgblinkQuiet -o "$gbtemp" -l "$test"/script.link "$otemp" "$gbtemp2"
+tryCmpRom "$test"/ref.out.bin
+evaluateTest
+
 test="section-union/good"
 startTest
 "$RGBASM" -o "$otemp" "$test"/a.asm