Error messages note when a symbol has been purged (#1453)

include/asm/symbol.hpp

@@ -95,6 +95,8 @@ Symbol *sym_Ref(std::string const &symName);
 Symbol *sym_AddString(std::string const &symName, std::shared_ptr<std::string> value);
 Symbol *sym_RedefString(std::string const &symName, std::shared_ptr<std::string> value);
 void sym_Purge(std::string const &symName);
+bool sym_IsPurgedExact(std::string const &symName);
+bool sym_IsPurgedScoped(std::string const &symName);
 void sym_Init(time_t now);
 
 // Functions to save and restore the current symbol scope.

src/asm/fstack.cpp

@@ -333,6 +333,9 @@ void fstk_RunMacro(std::string const &macroName, std::shared_ptr<MacroArgs> macr
 	Symbol *macro = sym_FindExactSymbol(macroName);
 
 	if (!macro) {
+		if (sym_IsPurgedExact(macroName))
+			error("Macro \"%s\" not defined; it was purged\n", macroName.c_str());
+		else
 			error("Macro \"%s\" not defined\n", macroName.c_str());
 		return;
 	}

src/asm/lexer.cpp

@@ -604,6 +604,9 @@ static uint32_t readBracketedMacroArgNum() {
 		Symbol const *sym = sym_FindScopedValidSymbol(symName);
 
 		if (!sym) {
+			if (sym_IsPurgedScoped(symName))
+				error("Bracketed symbol \"%s\" does not exist; it was purged\n", symName.c_str());
+			else
 				error("Bracketed symbol \"%s\" does not exist\n", symName.c_str());
 			num = 0;
 			symbolError = true;
@@ -1209,6 +1212,9 @@ static std::shared_ptr<std::string> readInterpolation(size_t depth) {
 	Symbol const *sym = sym_FindScopedValidSymbol(fmtBuf);
 
 	if (!sym || !sym->isDefined()) {
+		if (sym_IsPurgedScoped(fmtBuf))
+			error("Interpolated symbol \"%s\" does not exist; it was purged\n", fmtBuf.c_str());
+		else
 			error("Interpolated symbol \"%s\" does not exist\n", fmtBuf.c_str());
 	} else if (sym->type == SYM_EQUS) {
 		auto buf = std::make_shared<std::string>();

src/asm/parser.y

@@ -1527,8 +1527,12 @@ string:
 	| POP_SECTION LPAREN scoped_anon_id RPAREN {
 		Symbol *sym = sym_FindScopedValidSymbol($3);
 
-		if (!sym)
+		if (!sym) {
+			if (sym_IsPurgedScoped($3))
+				fatalerror("Unknown symbol \"%s\"; it was purged\n", $3.c_str());
+			else
 				fatalerror("Unknown symbol \"%s\"\n", $3.c_str());
+		}
 		Section const *section = sym->getSection();
 
 		if (!section)

src/asm/rpn.cpp

@@ -82,6 +82,8 @@ void Expression::makeSymbol(std::string const &symName) {
 		isSymbol = true;
 
 		data = sym_IsPC(sym) ? "PC is not constant at assembly time"
+		                     : sym_IsPurgedScoped(symName)
+		                     ? "'"s + symName + "' is not constant at assembly time; it was purged"
 		                     : "'"s + symName + "' is not constant at assembly time";
 		sym = sym_Ref(symName);
 
@@ -122,7 +124,9 @@ void Expression::makeBankSymbol(std::string const &symName) {
 			// Symbol's section is known and bank is fixed
 			data = (int32_t)sym->getSection()->bank;
 		} else {
-			data = "\""s + symName + "\"'s bank is not known";
+			data = sym_IsPurgedScoped(symName)
+			     ? "\""s + symName + "\"'s bank is not known; it was purged"
+			     : "\""s + symName + "\"'s bank is not known";
 
 			size_t nameLen = sym->name.length() + 1; // Room for NUL!
 

src/asm/symbol.cpp

@@ -5,6 +5,7 @@
 #include <inttypes.h>
 #include <stdio.h>
 #include <unordered_map>
+#include <unordered_set>
 
 #include "error.hpp"
 #include "helpers.hpp" // assume
@@ -19,6 +20,7 @@
 using namespace std::literals;
 
 std::unordered_map<std::string, Symbol> symbols;
+std::unordered_set<std::string> purgedSymbols;
 
 static std::optional<std::string> labelScope = std::nullopt; // Current section's label scope
 static Symbol *PCSymbol;
@@ -158,11 +160,13 @@ Symbol const *sym_GetPC() {
 	return PCSymbol;
 }
 
-// Purge a symbol
 void sym_Purge(std::string const &symName) {
 	Symbol *sym = sym_FindScopedValidSymbol(symName);
 
 	if (!sym) {
+		if (sym_IsPurgedScoped(symName))
+			error("'%s' was already purged\n", symName.c_str());
+		else
 			error("'%s' not defined\n", symName.c_str());
 	} else if (sym->isBuiltin) {
 		error("Built-in symbol '%s' cannot be purged\n", symName.c_str());
@@ -176,10 +180,27 @@ void sym_Purge(std::string const &symName) {
 		// Do not keep a reference to the label's name after purging it
 		if (sym->name == labelScope)
 			labelScope = std::nullopt;
+		purgedSymbols.emplace(sym->name);
 		symbols.erase(sym->name);
 	}
 }
 
+bool sym_IsPurgedExact(std::string const &symName) {
+	return purgedSymbols.find(symName) != purgedSymbols.end();
+}
+
+bool sym_IsPurgedScoped(std::string const &symName) {
+	if (size_t dotPos = symName.find('.'); dotPos != std::string::npos) {
+		// Check for a nonsensical reference to a nested scoped symbol
+		if (symName.find('.', dotPos + 1) != std::string::npos)
+			return false;
+		// If auto-scoped local label, expand the name
+		if (dotPos == 0 && labelScope)
+			return sym_IsPurgedExact(*labelScope + symName);
+	}
+	return sym_IsPurgedExact(symName);
+}
+
 uint32_t sym_GetPCValue() {
 	Section const *sect = sect_GetSymbolSection();
 
@@ -218,6 +239,9 @@ uint32_t sym_GetConstantValue(std::string const &symName) {
 	if (Symbol const *sym = sym_FindScopedSymbol(symName); sym)
 		return sym->getConstantValue();
 
+	if (sym_IsPurgedScoped(symName))
+		error("'%s' not defined; it was purged\n", symName.c_str());
+	else
 		error("'%s' not defined\n", symName.c_str());
 	return 0;
 }
@@ -242,6 +266,7 @@ static Symbol *createNonrelocSymbol(std::string const &symName, bool numeric) {
 
 	if (!sym) {
 		sym = &createSymbol(symName);
+		purgedSymbols.erase(sym->name);
 	} else if (sym->isDefined()) {
 		error("'%s' already defined at ", symName.c_str());
 		dumpFilename(*sym);

test/asm/local-purge.err

@@ -1,5 +1,5 @@
 warning: local-purge.asm(7): [-Wpurge]
     Purging a label ".loc"
 error: local-purge.asm(8):
-    Interpolated symbol ".loc" does not exist
+    Interpolated symbol ".loc" does not exist; it was purged
 error: Assembly aborted (1 error)!

test/asm/sym-collision.err

@@ -1,5 +1,5 @@
 warning: sym-collision.asm(20): [-Wpurge]
     Purging a label "dork"
 error: sym-collision.asm(25):
-    Interpolated symbol "dork" does not exist
+    Interpolated symbol "dork" does not exist; it was purged
 error: Assembly aborted (1 error)!