Implement [[ inline fragments ]]

Fixes gbdev#500

include/asm/section.h

@@ -45,6 +45,7 @@ void out_NewSection(char const *name, uint32_t secttype, uint32_t org,
 void out_SetLoadSection(char const *name, uint32_t secttype, uint32_t org,
 			struct SectionSpec const *attributes);
 void out_EndLoadSection(void);
+void out_PushInlineFragmentSection(void);
 
 struct Section *sect_GetSymbolSection(void);
 uint32_t sect_GetSymbolOffset(void);

src/asm/lexer.c

@@ -1251,6 +1251,8 @@ static void readGfxConstant(void)
 
 static bool startsIdentifier(int c)
 {
+	// Anonymous labels internally start with '!'
+	// Section fragment labels internally start with '$'
 	return (c <= 'Z' && c >= 'A') || (c <= 'z' && c >= 'a') || c == '.' || c == '_';
 }
 
@@ -1648,10 +1650,6 @@ static int yylex_NORMAL(void)
 			yylval.tzSym[1] = '\0';
 			return T_ID;
 
-		case '[':
-			return T_LBRACK;
-		case ']':
-			return T_RBRACK;
 		case '(':
 			return T_LPAREN;
 		case ')':
@@ -1661,6 +1659,18 @@ static int yylex_NORMAL(void)
 
 		/* Handle ambiguous 1- or 2-char tokens */
 
+		case '[': /* Either [ or [[ */
+			if (peek(0) == '[') {
+				shiftChars(1);
+				return T_2LBRACK;
+			}
+			return T_LBRACK;
+		case ']': /* Either ] or ]] */
+			if (peek(0) == ']') {
+				shiftChars(1);
+				return T_2RBRACK;
+			}
+			return T_RBRACK;
 		case '*': /* Either MUL or EXP */
 			if (peek(0) == '*') {
 				shiftChars(1);

src/asm/parser.y

@@ -38,6 +38,7 @@
 
 static bool executeElseBlock; /* If this is set, ELIFs cannot be executed anymore */
 static struct CaptureBody captureBody; /* Captures a REPT/FOR or MACRO */
+static uint32_t inlineFragmentID = 0; /* Incrementing unique ID for inline fragment labels */
 
 static void upperstring(char *dest, char const *src)
 {
@@ -404,6 +405,7 @@ enum {
 	} forArgs;
 	struct StrFmtArgList strfmtArgs;
 	bool hasEmpty; // Whether `db`, `dw`, `dl` argument lists contain any empty entries
+	char inlineFragmentName[12]; // space for "$4294967295" + '\0'
 }
 
 %type	<sVal>		relocexpr
@@ -430,12 +432,15 @@ enum {
 %type	<nConstValue>	sectorg
 %type	<sectSpec>	sectattrs
 
+%type	<inlineFragmentName>	inline_fragment
+
 %token	<nConstValue>	T_NUMBER "number"
 %token	<tzString>	T_STRING "string"
 
 %token	T_COMMA ","
 %token	T_COLON ":"
 %token	T_LBRACK "[" T_RBRACK "]"
+%token	T_2LBRACK "[[" T_2RBRACK "]]"
 %token	T_LPAREN "(" T_RPAREN ")"
 %token	T_NEWLINE "newline"
 
@@ -1206,6 +1211,7 @@ reloc_16bit	: relocexpr {
 				warning(WARNING_TRUNCATION, "Expression must be 16-bit\n");
 			$$ = $1;
 		}
+		| inline_fragment { rpn_Symbol(&$$, $1); }
 ;
 
 reloc_16bit_no_str : relocexpr_no_str {
@@ -1214,8 +1220,18 @@ reloc_16bit_no_str : relocexpr_no_str {
 				warning(WARNING_TRUNCATION, "Expression must be 16-bit\n");
 			$$ = $1;
 		}
+		| inline_fragment { rpn_Symbol(&$$, $1); }
 ;
 
+inline_fragment	: T_2LBRACK {
+			out_PushInlineFragmentSection();
+			sprintf($<inlineFragmentName>$, "$%" PRIu32, inlineFragmentID++);
+			sym_AddLabel($<inlineFragmentName>$);
+		} asmfile T_2RBRACK {
+			out_PopSection();
+			strcpy($$, $<inlineFragmentName>2);
+		}
+;
 
 relocexpr	: relocexpr_no_str
 		| string {

src/asm/section.c

@@ -249,7 +249,48 @@ static void mergeSections(struct Section *sect, enum SectionType type, uint32_t
 #undef fail
 
 /*
- * Find a section by name and type. If it doesn't exist, create it
+ * Create a new section, not yet in the list.
+ */
+static struct Section *createSection(char const *name, enum SectionType type,
+				     uint32_t org, uint32_t bank, uint8_t alignment,
+				     uint16_t alignOffset, enum SectionModifier mod)
+{
+	struct Section *sect = malloc(sizeof(*sect));
+
+	if (sect == NULL)
+		fatalerror("Not enough memory for section: %s\n", strerror(errno));
+
+	sect->name = strdup(name);
+	if (sect->name == NULL)
+		fatalerror("Not enough memory for section name: %s\n", strerror(errno));
+
+	sect->type = type;
+	sect->modifier = mod;
+	sect->size = 0;
+	sect->org = org;
+	sect->bank = bank;
+	sect->align = alignment;
+	sect->alignOfs = alignOffset;
+	sect->next = NULL;
+	sect->patches = NULL;
+
+	/* It is only needed to allocate memory for ROM sections. */
+	if (sect_HasData(type)) {
+		uint32_t sectsize;
+
+		sectsize = maxsize[type];
+		sect->data = malloc(sectsize);
+		if (sect->data == NULL)
+			fatalerror("Not enough memory for section: %s\n", strerror(errno));
+	} else {
+		sect->data = NULL;
+	}
+
+	return sect;
+}
+
+/*
+ * Find a section by name and type. If it doesn't exist, create it.
  */
 static struct Section *getSection(char const *name, enum SectionType type, uint32_t org,
 				  struct SectionSpec const *attrs, enum SectionModifier mod)
@@ -320,34 +361,7 @@ static struct Section *getSection(char const *name, enum SectionType type, uint3
 		return sect;
 	}
 
-	sect = malloc(sizeof(*sect));
-	if (sect == NULL)
-		fatalerror("Not enough memory for section: %s\n", strerror(errno));
-
-	sect->name = strdup(name);
-	if (sect->name == NULL)
-		fatalerror("Not enough memory for section name: %s\n", strerror(errno));
-
-	sect->type = type;
-	sect->modifier = mod;
-	sect->size = 0;
-	sect->org = org;
-	sect->bank = bank;
-	sect->align = alignment;
-	sect->alignOfs = alignOffset;
-	sect->patches = NULL;
-
-	/* It is only needed to allocate memory for ROM sections. */
-	if (sect_HasData(type)) {
-		uint32_t sectsize;
-
-		sectsize = maxsize[type];
-		sect->data = malloc(sectsize);
-		if (sect->data == NULL)
-			fatalerror("Not enough memory for section: %s\n", strerror(errno));
-	} else {
-		sect->data = NULL;
-	}
+	sect = createSection(name, type, org, bank, alignment, alignOffset, mod);
 
 	// Add the new section to the list (order doesn't matter)
 	sect->next = pSectionList;
@@ -416,6 +430,35 @@ void out_EndLoadSection(void)
 	loadOffset = 0;
 }
 
+void out_PushInlineFragmentSection(void)
+{
+	checkcodesection();
+
+	if (currentLoadSection)
+		fatalerror("`LOAD` blocks cannot contain inline fragments\n");
+
+	struct Section *sect = pCurrentSection;
+
+	// A section containing an inline fragment has to become a fragment too
+	sect->modifier = SECTION_FRAGMENT;
+
+	out_PushSection();
+
+	// 'SECTION "...", ROM0, BANK[0]' is not allowed
+	uint32_t bank = sect->bank == 0 ? -1 : sect->bank;
+
+	struct Section *newSect = createSection(sect->name, sect->type, -1, bank, 0, 0,
+						SECTION_FRAGMENT);
+
+	// Add the inline section fragment to the list (after the section containing it)
+	newSect->next = sect->next;
+	sect->next = newSect;
+
+	changeSection();
+	curOffset = newSect->size;
+	pCurrentSection = newSect;
+}
+
 struct Section *sect_GetSymbolSection(void)
 {
 	return currentLoadSection ? currentLoadSection : pCurrentSection;