Add NewDebugSymbol(): stabs symbol factory

This function, currently unused, generates a stabs
debugging symbol, as documented here:

https://sourceware.org/gdb/onlinedocs/stabs.html

It can be used to process stabs directives, also
documented at the above URL, generated by HLL
compilers such as GCC, as well as to generate line
number and file name debug symbols when assembling
hand-coded assembly files with the -g option.

v2:
-Don't double-init stabs symbol fields
-Consistently use tabs, not spaces

object.c

@@ -180,29 +180,49 @@ _________________________________________________
 uint8_t * AddBSDSymEntry(uint8_t * buf, SYM * sym, int globflag)
 {
 	chptr = buf;						// Point to buffer for depositing longs
-	D_long(strindx);					// Deposit the symbol string index
+	if (sym->sname)
+	{
+		D_long(strindx);				// Deposit the symbol string index
+	}
+    else
+	{
+		D_long(0);						// Deposit special NULL string index
+	}
 
 	uint16_t w1 = sym->sattr;			// Obtain symbol attributes
 	uint32_t z = 0;						// Initialize resulting symbol flags
 
-	if (w1 & EQUATED)
+	if (sym->stype == DBGSYM)
 	{
-		z = 0x02000000;					// Set equated flag
+		// Debug symbols hard-code the a.out symbol type in the st_type field
+		// and can include additional type-specific data in the a.out symbol
+		// "other" and "description" fields, both packed into this same dword.
+		z = sym->st_type << 24;
+		z |= sym->st_other << 16;
+		z |= sym->st_desc;
 	}
-
-	// If a symbol is both EQUd and flagged as TBD then we let the latter take
-	// precedence. Otherwise the linker will not even bother trying to relocate
-	// the address during link time.
-
-	switch (w1 & TDB)
+	else
 	{
-	case TEXT: z = 0x04000000; break;	// Set TEXT segment flag
-	case DATA: z = 0x06000000; break;	// Set DATA segment flag
-	case BSS : z = 0x08000000; break;	// Set BSS segment flag
-	}
+		// Translate rmac symbol attributes to an a.out symbol type.
+		if (w1 & EQUATED)
+		{
+			z = 0x02000000;					// Set equated flag
+		}
 
-	if (globflag)
-		z |= 0x01000000;				// Set global flag if requested
+		// If a symbol is both EQUd and flagged as TBD then we let the latter
+		// take precedence. Otherwise the linker will not even bother trying to
+		// relocate the address during link time.
+
+		switch (w1 & TDB)
+		{
+		case TEXT: z = 0x04000000; break;	// Set TEXT segment flag
+		case DATA: z = 0x06000000; break;	// Set DATA segment flag
+		case BSS : z = 0x08000000; break;	// Set BSS segment flag
+		}
+
+		if (globflag)
+			z |= 0x01000000;				// Set global flag if requested
+	}
 
 	D_long(z);							// Deposit symbol attribute
 	z = sym->svalue;					// Obtain symbol value
@@ -214,8 +234,11 @@ uint8_t * AddBSDSymEntry(uint8_t * buf, SYM * sym, int globflag)
 		z += sect[DATA].sloc;			// If BSS add DATA segment size
 
 	D_long(z);							// Deposit symbol value
-	strcpy(strtable + strindx, sym->sname);
-	strindx += strlen(sym->sname) + 1;	// Incr string index incl null terminate
+	if (sym->sname)
+	{
+		strcpy(strtable + strindx, sym->sname);
+		strindx += strlen(sym->sname) + 1;	// Incr string index incl null terminate
+	}
 	buf += 12;							// Increment buffer to next record
 	symsize += 12;						// Increment symbol table size
 

rmac.h

@@ -222,6 +222,7 @@ PTR
 #define LABEL        0			// User-defined symbol
 #define MACRO        1			// Macro definition
 #define MACARG       2			// Macro argument
+#define DBGSYM       3			// stabs debug symbol
 #define SY_UNDEF     -1			// Undefined (lookup never matches it)
 
 // Symbol and expression attributes

symbol.c

@@ -88,7 +88,7 @@ SYM * NewSymbol(uint8_t * name, int type, int envno)
 	}
 
 	// Fill-in the symbol
-	symbol->sname  = strdup(name);
+	symbol->sname  = name ? strdup(name) : NULL;
 	symbol->stype  = (uint8_t)type;
 	symbol->senv   = (uint16_t)envno;
 	// We don't set this as DEFINED, as it could be a forward reference!
@@ -99,14 +99,22 @@ SYM * NewSymbol(uint8_t * name, int type, int envno)
 	symbol->svalue = 0;
 	symbol->sorder = NULL;
 	symbol->uid    = currentUID++;
+	// We don't set st_type, st_desc, or st_other here because they are only
+	// used by stabs debug symbols, which are always initialized by
+	// NewDebugSymbol(), which always sets these fields. Hence, initializing
+	// them here would be redundant.
 
-	// Record filename the symbol is defined (for now only used by macro error reporting)
+	// Record filename the symbol is defined (Used by macro error reporting and some debug symbols)
 	symbol->cfileno = cfileno;
 
-	// Install symbol in the symbol table
-	int hash = HashSymbol(name, envno);
-	symbol->snext = symbolTable[hash];
-	symbolTable[hash] = symbol;
+	// Don't hash debug symbols: they are never looked up and may have no name.
+	if (type != DBGSYM)
+	{
+		// Install symbol in the symbol table
+		int hash = HashSymbol(name, envno);
+		symbol->snext = symbolTable[hash];
+		symbolTable[hash] = symbol;
+	}
 
 	// Append symbol to the symbol-order list
 	if (sorder == NULL)
@@ -235,7 +243,16 @@ uint32_t AssignSymbolNos(uint8_t * buf, uint8_t *(* construct)())
 	// them. We also pick which symbols should be global or not here.
 	for(SYM * sy=sdecl; sy!=NULL; sy=sy->sdecl)
 	{
-		// Skip non-labels
+		// Always export debug symbols. Don't force them global.
+		if (DBGSYM == sy->stype) {
+			sy->senv = scount++;
+
+			if (buf != NULL)
+				buf = construct(buf, sy, 0);
+			continue;
+		}
+
+		// Skip non-labels.
 		if (sy->stype != LABEL)
 			continue;
 
@@ -547,3 +564,19 @@ int symtable(void)
 
 	return 0;
 }
+
+SYM * NewDebugSymbol(uint8_t * str, uint8_t type, uint8_t other, uint16_t desc)
+{
+	SYM * symbol = NewSymbol(str, DBGSYM, 0);
+
+	if (NULL == symbol)
+		return NULL;
+
+	AddToSymbolDeclarationList(symbol);
+
+	symbol->st_type = type;
+	symbol->st_other = other;
+	symbol->st_desc = desc;
+
+	return symbol;
+}

symbol.h

@@ -37,6 +37,9 @@ SYM
 	LLIST * last;			// * -> end of macro linked list
 	uint16_t cfileno;		// File the macro is defined in
 	uint32_t uid;			// Symbol's unique ID
+	uint8_t st_type;		// stabs debug symbol's "type" field
+	uint8_t st_other;		// stabs debug symbol's "other" field
+	uint16_t st_desc;		// stabs debug symbol's "description" field
 };
 
 // Exported variables
@@ -54,6 +57,7 @@ uint32_t AssignSymbolNos(uint8_t *, uint8_t *(*)());
 uint32_t AssignSymbolNosELF(uint8_t *, uint8_t *(*)());
 void DumpLODSymbols(void);
 uint8_t * GetSymbolNameByUID(uint32_t);
+SYM * NewDebugSymbol(uint8_t *, uint8_t, uint8_t, uint16_t);
 
 #endif // __SYMBOL_H__