From 6e85377d7a5733dccd811429b58866090393b8a6 Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Fri, 12 Nov 2021 00:19:58 +0900
Subject: [PATCH] [cexpr] Support variable assignment

I might have to add code to block it when necessary, but it's needed for
axis recipe parsing.
---
 libs/util/cexpr-lex.l   |  9 +++++++++
 libs/util/cexpr-parse.y | 16 +++++++++-------
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/libs/util/cexpr-lex.l b/libs/util/cexpr-lex.l
index 3fafef8e6..026f7eea2 100644
--- a/libs/util/cexpr-lex.l
+++ b/libs/util/cexpr-lex.l
@@ -166,15 +166,23 @@ STRING		\"(\\.|[^"\\])*\"
 					}
 
 [+\-*/&|^%]=		{
+						yylval->op = yytext[0];
+						return ASX;
 					}
 
 "%%="				{
+						yylval->op = MOD;
+						return ASX;
 					}
 
 "<<="				{
+						yylval->op = SHL;
+						return ASX;
 					}
 
 ">>="				{
+						yylval->op = SHR;
+						return ASX;
 					}
 
 [!(){}.*/&|^~+\-=\[\];,#%?:] {
@@ -182,6 +190,7 @@ STRING		\"(\\.|[^"\\])*\"
 					}
 
 "%%"				{
+						return MOD;
 					}
 
 "<<"				return SHL;
diff --git a/libs/util/cexpr-parse.y b/libs/util/cexpr-parse.y
index fca9171af..46eaae7fe 100644
--- a/libs/util/cexpr-parse.y
+++ b/libs/util/cexpr-parse.y
@@ -51,8 +51,8 @@
 
 #include "QF/cexpr.h"
 
-static void assign_expr (exprval_t *dst, const exprval_t *src,
-						 exprctx_t *context);
+static exprval_t *assign_expr (exprval_t *dst, const exprval_t *src,
+							   exprctx_t *context);
 static exprval_t *binary_expr (int op, const exprval_t *a, const exprval_t *b,
 							   exprctx_t *context);
 static exprval_t *field_expr (const exprval_t *a, const exprval_t *b,
@@ -138,6 +138,7 @@ uexpr
 
 expr
 	: uexpr
+	| expr '=' expr		{ $$ = assign_expr ($1, $3, context); }
 	| expr SHL expr		{ $$ = binary_expr (SHL, $1, $3, context); }
 	| expr SHR expr		{ $$ = binary_expr (SHR, $1, $3, context); }
 	| expr '+' expr		{ $$ = binary_expr ('+', $1, $3, context); }
@@ -184,16 +185,16 @@ arg_expr
 
 %%
 
-static void
+static exprval_t *
 assign_expr (exprval_t *dst, const exprval_t *src, exprctx_t *context)
 {
 	binop_t    *binop;
-	if (!src) {
-		return;
+	if (!dst || !src) {
+		return 0;
 	}
 	if (dst->type == &cexpr_exprval) {
 		*(exprval_t **) dst->value = (exprval_t *) src;
-		return;
+		return dst;
 	}
 	binop = cexpr_find_cast (dst->type, src->type);
 	if (binop && binop->op) {
@@ -203,10 +204,11 @@ assign_expr (exprval_t *dst, const exprval_t *src, exprctx_t *context)
 			cexpr_error (context,
 						 "type mismatch in expression result: %s = %s",
 						 dst->type->name, src->type->name);
-			return;
+			return dst;
 		}
 		memcpy (dst->value, src->value, dst->type->size);
 	}
+	return dst;
 }
 
 static exprval_t *