From 041d9ff133a944580bc39ba42d053379df33330c Mon Sep 17 00:00:00 2001
From: Andrew Yourtchenko <ayourtch@gmail.com>
Date: Tue, 26 Nov 2019 01:35:09 +0100
Subject: [PATCH] Implement "%rdefine", which aims to help with symbolic
 references to registers. The usage is as follows:

%rdefine foo_test ax
        mov foo_test, 1
%rdefine bar_test ax
        mov bar_test, 2

the result will generate:
        mov ax, 1
        mov ax, 2

however, uncommenting either of the
commented above lines will cause error.

Under the hood, rdefine defines an additional macro rdefine_<expand>, which
refers back to the name of the rdefine argument - this way we can track
which rdefines refer to which registers, and undefine them automatically
as needed.
---
 asm/pptok.dat    |  1 +
 asm/preproc.c    | 22 ++++++++++++++++++++++
 test/rdefine.asm |  6 ++++++
 3 files changed, 29 insertions(+)
 create mode 100644 test/rdefine.asm

diff --git a/asm/pptok.dat b/asm/pptok.dat
index b6285c36..bb0b7cec 100644
--- a/asm/pptok.dat
+++ b/asm/pptok.dat
@@ -61,6 +61,7 @@
 %!assign
 %!defalias
 %!define
+%!rdefine
 %!defstr
 %!deftok
 %!macro
diff --git a/asm/preproc.c b/asm/preproc.c
index 41a7c6fb..a9d06c3f 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -4049,6 +4049,7 @@ issue_error:
         break;
 
     case PP_DEFINE:
+    case PP_RDEFINE:
     case PP_XDEFINE:
     case PP_DEFALIAS:
     {
@@ -4101,6 +4102,27 @@ issue_error:
          * carefully re-terminated after chopping off the expansion
          * from the end).
          */
+	if (op == PP_RDEFINE) {
+		const char *target = tok_text(macro_start);
+		int sz = strlen(target)+1+strlen("rdefine_");
+		char *rdef_name = nasm_malloc(sz);
+		SMacro *rdef_defn = 0;
+		Token *t = make_tok_qstr(NULL, mname);
+		SMacro tmpl2;
+
+		/* fprintf(stderr, "RDEFINE %s %s\n", mname, target); */
+		snprintf(rdef_name, sz, "rdefine_%s", target);
+		if (smacro_defined(NULL, rdef_name, 0, &rdef_defn, casesense, 0)) {
+			const char *expansion = unquote_token(rdef_defn->expansion);
+			/* fprintf(stderr, "Already defined %s as %s\n", rdef_name, expansion); */
+			/* fprintf(stderr, "undefining %s\n", expansion); */
+			undef_smacro(expansion, false);
+			/* fprintf(stderr, "undefining %s\n", rdef_name); */
+			undef_smacro(expansion, false);
+		}
+		nasm_zero(tmpl2);
+		define_smacro(rdef_name, casesense, t, &tmpl2);
+	}
         define_smacro(mname, casesense, macro_start, &tmpl);
         break;
     }
diff --git a/test/rdefine.asm b/test/rdefine.asm
new file mode 100644
index 00000000..c888392a
--- /dev/null
+++ b/test/rdefine.asm
@@ -0,0 +1,6 @@
+%rdefine foobar_test ax
+	mov foobar_test, 1
+#        mov foobar2_test, 2
+%rdefine foobar2_test ax
+#        mov foobar_test, 3
+        mov foobar2_test, 4
-- 
2.17.1