From 944c5f0cd0a677f18390fa9367cb44d6aa680d2f Mon Sep 17 00:00:00 2001
From: Quinn <3379314+quinnyo@users.noreply.github.com>
Date: Thu, 26 Oct 2023 06:34:56 +1000
Subject: [PATCH] Implement order-independent purge (#1173)

Each symbol passed to purge is collected in a list before mass removal.
Fixes the issue described in gbdev/rgbds issue #1152.

---------

Co-authored-by: Rangi42 <remy.oukaour+rangi42@gmail.com>
---
 include/asm/lexer.h         |  7 ++++++
 src/asm/parser.y            | 50 ++++++++++++++++++++++++++++++++-----
 test/asm/purge-deferred.asm | 11 ++++++++
 test/asm/purge-deferred.err |  0
 test/asm/purge-deferred.out |  0
 5 files changed, 62 insertions(+), 6 deletions(-)
 create mode 100644 test/asm/purge-deferred.asm
 create mode 100644 test/asm/purge-deferred.err
 create mode 100644 test/asm/purge-deferred.out

diff --git a/include/asm/lexer.h b/include/asm/lexer.h
index a88b66bd8..91bb0a8ec 100644
--- a/include/asm/lexer.h
+++ b/include/asm/lexer.h
@@ -97,4 +97,11 @@ struct DsArgList {
 	struct Expression *args;
 };
 
+#define INITIAL_PURGE_ARG_SIZE 2
+struct PurgeArgList {
+	size_t nbArgs;
+	size_t capacity;
+	char **args;
+};
+
 #endif // RGBDS_ASM_LEXER_H
diff --git a/src/asm/parser.y b/src/asm/parser.y
index 21d6a5362..89d6164a1 100644
--- a/src/asm/parser.y
+++ b/src/asm/parser.y
@@ -398,6 +398,35 @@ static void freeDsArgList(struct DsArgList *args)
 	free(args->args);
 }
 
+static void initPurgeArgList(struct PurgeArgList *args)
+{
+	args->nbArgs = 0;
+	args->capacity = INITIAL_PURGE_ARG_SIZE;
+	args->args = malloc(args->capacity * sizeof(*args->args));
+	if (!args->args)
+		fatalerror("Failed to allocate memory for purge arg list: %s\n",
+			   strerror(errno));
+}
+
+static void appendPurgeArgList(struct PurgeArgList *args, char *arg)
+{
+	if (args->nbArgs == args->capacity) {
+		args->capacity = (args->capacity + 1) * 2;
+		args->args = realloc(args->args, args->capacity * sizeof(*args->args));
+		if (!args->args)
+			fatalerror("realloc error while resizing purge arg list: %s\n",
+				   strerror(errno));
+	}
+	args->args[args->nbArgs++] = arg;
+}
+
+static void freePurgeArgList(struct PurgeArgList *args)
+{
+	for (size_t i = 0; i < args->nbArgs; i++)
+		free(args->args[i]);
+	free(args->args);
+}
+
 static void failAssert(enum AssertionType type)
 {
 	switch (type) {
@@ -481,6 +510,7 @@ enum {
 	struct MacroArgs *macroArg;
 	enum AssertionType assertType;
 	struct DsArgList dsArgs;
+	struct PurgeArgList purgeArgs;
 	struct {
 		int32_t start;
 		int32_t stop;
@@ -636,6 +666,8 @@ enum {
 
 %type	<dsArgs> ds_args
 
+%type	<purgeArgs> purge_args
+
 %type	<forArgs> for_args
 
 %token	T_Z80_ADC "adc" T_Z80_ADD "add" T_Z80_AND "and"
@@ -1199,16 +1231,22 @@ redef_equs	: redef_id T_POP_EQUS string { sym_RedefString($1, $3); }
 
 purge		: T_POP_PURGE {
 			lexer_ToggleStringExpansion(false);
-		} purge_list trailing_comma {
+		} purge_args trailing_comma {
+			for (uint32_t i = 0; i < $3.nbArgs; i++)
+				sym_Purge($3.args[i]);
+			freePurgeArgList(&$3);
 			lexer_ToggleStringExpansion(true);
 		}
 ;
 
-purge_list	: purge_list_entry
-		| purge_list T_COMMA purge_list_entry
-;
-
-purge_list_entry : scoped_id { sym_Purge($1); }
+purge_args	: scoped_id {
+			initPurgeArgList(&$$);
+			appendPurgeArgList(&$$, strdup($1));
+		}
+		| purge_args T_COMMA scoped_id {
+			appendPurgeArgList(&$1, strdup($3));
+			$$ = $1;
+		}
 ;
 
 export		: T_POP_EXPORT export_list trailing_comma
diff --git a/test/asm/purge-deferred.asm b/test/asm/purge-deferred.asm
new file mode 100644
index 000000000..07ee0c012
--- /dev/null
+++ b/test/asm/purge-deferred.asm
@@ -0,0 +1,11 @@
+DEF prefix EQUS "cool"
+DEF {prefix}banana EQU 1
+
+ASSERT DEF(prefix)
+ASSERT DEF(coolbanana)
+
+; purging `prefix` should not prevent expanding it to purge `coolbanana`
+PURGE prefix, {prefix}banana
+
+ASSERT !DEF(prefix)
+ASSERT !DEF(coolbanana)
diff --git a/test/asm/purge-deferred.err b/test/asm/purge-deferred.err
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/asm/purge-deferred.out b/test/asm/purge-deferred.out
new file mode 100644
index 000000000..e69de29bb