Use std::string_view for macro bodies (#1326)

This removes the last use of `strdup`

This required making a lot of related pointers be `const`.
That in turn conflicted with the need to `munmap()` a pointer
eventually, which was similar to the need to eventually `free()`
an `Expansion`'s contents, so I used the same solution of a
`union`. That lets us normally use the `const` pointer for
`const` correctness, and the non-`const` one for the not-really-
mutating destruction cases.

include/asm/fstack.hpp

@@ -61,9 +61,9 @@ std::string *fstk_FindFile(char const *path);
 bool yywrap();
 void fstk_RunInclude(char const *path);
 void fstk_RunMacro(char const *macroName, MacroArgs *args);
-void fstk_RunRept(uint32_t count, int32_t reptLineNo, char *body, size_t size);
+void fstk_RunRept(uint32_t count, int32_t reptLineNo, char const *body, size_t size);
 void fstk_RunFor(char const *symName, int32_t start, int32_t stop, int32_t step,
-		     int32_t reptLineNo, char *body, size_t size);
+		     int32_t reptLineNo, char const *body, size_t size);
 void fstk_StopRept();
 bool fstk_Break();
 

include/asm/lexer.hpp

@@ -30,7 +30,7 @@ struct Expansion {
 	std::optional<std::string> name;
 	union {
 		char const *unowned;
-		char *owned;
+		char *owned; // Non-`const` only so it can be `free()`d
 	} contents;
 	size_t size; // Length of the contents
 	size_t offset; // Cursor into the contents
@@ -43,7 +43,10 @@ struct IfStackEntry {
 };
 
 struct MmappedLexerState {
-	char *ptr; // Technically `const` during the lexer's execution
+	union {
+		char const *unreferenced;
+		char *referenced; // Non-`const` only so it can be `munmap()`ped
+	} ptr;
 	size_t size;
 	size_t offset;
 	bool isReferenced; // If a macro in this file requires not unmapping it
@@ -121,7 +124,8 @@ static inline void lexer_SetGfxDigits(char const digits[4])
 
 // `path` is referenced, but not held onto..!
 bool lexer_OpenFile(LexerState &state, char const *path);
-void lexer_OpenFileView(LexerState &state, char const *path, char *buf, size_t size, uint32_t lineNo);
+void lexer_OpenFileView(LexerState &state, char const *path, char const *buf, size_t size,
+			uint32_t lineNo);
 void lexer_RestartRept(uint32_t lineNo);
 void lexer_CleanupState(LexerState &state);
 void lexer_Init();
@@ -138,7 +142,7 @@ void lexer_ReachELSEBlock();
 
 struct CaptureBody {
 	uint32_t lineNo;
-	char *body;
+	char const *body;
 	size_t size;
 };
 

include/asm/symbol.hpp

@@ -6,6 +6,7 @@
 #include <stdint.h>
 #include <string>
 #include <string.h>
+#include <string_view>
 #include <time.h>
 
 #include "asm/section.hpp"
@@ -23,12 +24,6 @@ enum SymbolType {
 	SYM_REF // Forward reference to a label
 };
 
-// Only used in an anonymous union by `Symbol`
-struct strValue {
-	size_t size;
-	char *value;
-};
-
 struct Symbol; // For the `sym_IsPC` forward declaration
 bool sym_IsPC(Symbol const *sym); // For the inline `getSection` method
 
@@ -43,14 +38,11 @@ struct Symbol {
 
 	bool hasCallback;
 	union {
-		// If isNumeric()
-		int32_t value;
-		int32_t (*numCallback)(); // If hasCallback
-		// For SYM_MACRO
-		strValue macro;
-		// For SYM_EQUS
-		strValue equs;
-		char const *(*strCallback)(); // If hasCallback
+		int32_t value; // If isNumeric()
+		int32_t (*numCallback)(); // If isNumeric() and hasCallback
+		std::string_view *macro; // For SYM_MACRO
+		std::string *equs; // For SYM_EQUS
+		char const *(*strCallback)(); // For SYM_EQUS if hasCallback
 	};
 
 	uint32_t ID; // ID of the symbol in the object file (-1 if none)
@@ -71,7 +63,7 @@ struct Symbol {
 
 	int32_t getValue() const;
 	uint32_t getConstantValue() const;
-	char const *getStringValue() const { return hasCallback ? strCallback() : equs.value; }
+	char const *getStringValue() const { return hasCallback ? strCallback() : equs->c_str(); }
 };
 
 void sym_ForEach(void (*func)(Symbol *));
@@ -94,7 +86,7 @@ Symbol *sym_FindScopedSymbol(char const *symName);
 // Find a scoped symbol by name; do not return `@` or `_NARG` when they have no value
 Symbol *sym_FindScopedValidSymbol(char const *symName);
 Symbol const *sym_GetPC();
-Symbol *sym_AddMacro(char const *symName, int32_t defLineNo, char *body, size_t size);
+Symbol *sym_AddMacro(char const *symName, int32_t defLineNo, char const *body, size_t size);
 Symbol *sym_Ref(char const *symName);
 Symbol *sym_AddString(char const *symName, char const *value);
 Symbol *sym_RedefString(char const *symName, char const *value);