GuString is now an ordinary C string - it makes live easier. In addition PgfSymbolKS, PgfExprFun and PgfLiteralStr now keep their strings as embedded flexible arrays. The latest change gives us the same compactness as the old representation but it is a lot easier to use.

src/runtime/c/pgf/expr.h

@@ -37,7 +37,7 @@ typedef enum {
 } PgfLiteralTag;
 
 typedef struct {
-	GuString val;
+	char val[0];  // a flexible array that contains the value
 } PgfLiteralStr;
 
 typedef struct {
@@ -102,7 +102,7 @@ typedef struct {
 } PgfExprMeta;
 
 typedef struct {
-	PgfCId fun;
+	char fun[0];
 } PgfExprFun;
 
 typedef struct {