From 5db2aed1297e7590beb35c43fa5ae40c44e2b686 Mon Sep 17 00:00:00 2001
From: Kugel Fuhr <98353208+kugelfuhr@users.noreply.github.com>
Date: Thu, 26 Jun 2025 07:40:04 +0200
Subject: [PATCH] Allow "sp" as an alias for "c_sp" for backwards
 compatibility. Using it will work but generates a linker warning. Added a
 test to check for this warning.

---
 asminc/zeropage.inc                         |  6 ++++++
 libsrc/runtime/sp-compat.s                  | 11 +++++++++++
 test/asm/listing/ref/sp-compat.ld65err2-ref |  1 +
 test/asm/listing/sp-compat.s                |  7 +++++++
 4 files changed, 25 insertions(+)
 create mode 100644 libsrc/runtime/sp-compat.s
 create mode 100644 test/asm/listing/ref/sp-compat.ld65err2-ref
 create mode 100644 test/asm/listing/sp-compat.s

diff --git a/asminc/zeropage.inc b/asminc/zeropage.inc
index 5285779ba..2d4b144db 100644
--- a/asminc/zeropage.inc
+++ b/asminc/zeropage.inc
@@ -13,6 +13,12 @@
         .globalzp       tmp1, tmp2, tmp3, tmp4
         .globalzp       regbank
 
+        ; The following symbol is supplied for compatibility reasons only, it
+        ; will get removed in future versions. Using it will cause a linker
+        ; warning.
+        .globalzp       sp
+
+
 ; The size of the register bank
 regbanksize     = 6
 
diff --git a/libsrc/runtime/sp-compat.s b/libsrc/runtime/sp-compat.s
new file mode 100644
index 000000000..797fef47b
--- /dev/null
+++ b/libsrc/runtime/sp-compat.s
@@ -0,0 +1,11 @@
+;
+; Kugelfuhr, 2025-06-26
+;
+; Add "sp" as an alias for "c_sp" so we don't break old code but emit a
+; linker warning if it is used. Added after renaming "sp" to "c_sp".
+;
+
+.include        "zeropage.inc"
+.export         sp := c_sp
+.assert         0, ldwarning, "Symbol 'sp' is deprecated - please use 'c_sp' instead"
+
diff --git a/test/asm/listing/ref/sp-compat.ld65err2-ref b/test/asm/listing/ref/sp-compat.ld65err2-ref
new file mode 100644
index 000000000..fe2611088
--- /dev/null
+++ b/test/asm/listing/ref/sp-compat.ld65err2-ref
@@ -0,0 +1 @@
+ld65: Warning: runtime/sp-compat.s:10: Symbol 'sp' is deprecated - please use 'c_sp' instead
diff --git a/test/asm/listing/sp-compat.s b/test/asm/listing/sp-compat.s
new file mode 100644
index 000000000..8c22a71d3
--- /dev/null
+++ b/test/asm/listing/sp-compat.s
@@ -0,0 +1,7 @@
+.include "zeropage.inc"
+
+.proc   _func
+        ldy     #0
+        lda     (sp),y
+        rts
+.endproc