From 9003d3e8fb283cc242e1d1962cdc17efe3749119 Mon Sep 17 00:00:00 2001
From: Johny Mattsson <johny.mattsson+github.gmail.com>
Date: Fri, 18 Dec 2015 13:10:48 +1100
Subject: [PATCH] Rework NODEMCU_MODULE() to not pull in extra gunk.

Third time lucky. I hope. Hi Terry.
---
 app/Makefile         | 11 ++++++-----
 app/include/module.h | 36 ++++++++++++++++++------------------
 ld/nodemcu.ld        |  4 ++--
 3 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/app/Makefile b/app/Makefile
index 83cb23cc..77e20ab1 100644
--- a/app/Makefile
+++ b/app/Makefile
@@ -88,8 +88,11 @@ COMPONENTS_eagle.app.v6 = 			\
 	tsl2561/tsl2561lib.a			\
 	modules/libmodules.a			\
 
-# Special consideration for modules to support NODEMCU_MODULE handling
-MODULES_LIB = $(filter %modules.a, $(DEP_LIBS_eagle.app.v6))
+# Inspect the modules library and work out which modules need to be linked.
+# For each enabled module, a symbol name of the form XYZ_module_selected is
+# returned. At link time those names are declared undefined, so those (and
+# only those) modules are pulled in.
+SELECTED_MODULE_SYMS=$(filter %_module_selected %module_selected1,$(shell $(NM) modules/.output/$(TARGET)/$(FLAVOR)/lib/libmodules.a))
 
 LINKFLAGS_eagle.app.v6 = 			\
 	-Wl,--gc-sections 			\
@@ -100,9 +103,7 @@ LINKFLAGS_eagle.app.v6 = 			\
 	-Wl,--no-check-sections 		\
 	-Wl,--wrap=_xtos_set_exception_handler	\
 	-Wl,-static 				\
-	-Wl,--whole-archive 			\
-	$(MODULES_LIB)				\
-	-Wl,--no-whole-archive			\
+	$(addprefix -u , $(SELECTED_MODULE_SYMS)) \
 	-Wl,--start-group 			\
 	-lc 					\
 	-lgcc 					\
diff --git a/app/include/module.h b/app/include/module.h
index 9f00a69a..919d5758 100644
--- a/app/include/module.h
+++ b/app/include/module.h
@@ -34,37 +34,37 @@
  * a foo function in your module.
  */
 
-#define MODULE_STRIFY__(x) #x
-#define MODULE_STRIFY_(x) MODULE_STRIFY__(x)
 #define MODULE_EXPAND_(x) x
 #define MODULE_PASTE_(x,y) x##y
+#define MODULE_EXPAND_PASTE_(x,y) MODULE_PASTE_(x,y)
 
-/* Given an uppercase name XYZ, look at the corresponding LUA_USE_MODULES_XYZ
- * and append that to the section name prefix (e.g. "lua_libs"). For an
- * included module, this will yield either ".lua_libs" (for an empty #define)
- * or ".lua_libs1" (if #defined to 1). The linker script will then
- * pick up all items in those sections and construct an array for us.
- * A non-included module ZZZ ends up in a section named
- * ".lua_libsLUA_USE_MODULES_ZZZ" which gets discarded by the linker (together
- * with the associated module code).
+#define LOCK_IN_SECTION(s) __attribute__((used,unused,section(s)))
+
+/* For the ROM table, we name the variable according to ( | denotes concat):
+ *   cfgname | _module_selected | LUA_USE_MODULES_##cfgname
+ * where the LUA_USE_MODULES_XYZ macro is first expanded to yield either
+ * an empty string (or 1) if the module has been enabled, or the literal
+ * LUA_USE_MOUDLE_XYZ in the case it hasn't. Thus, the name of the variable
+ * ends up looking either like XYZ_module_enabled, or if not enabled,
+ * XYZ_module_enabledLUA_USE_MODULES_XYZ.  This forms the basis for
+ * letting the build system detect automatically (via nm) which modules need
+ * to be linked in.
  */
-#define PICK_SECTION_(pfx, name) \
-   pfx MODULE_STRIFY_(MODULE_EXPAND_(LUA_USE_MODULES_ ## name))
-
 #define NODEMCU_MODULE(cfgname, luaname, map, initfunc) \
-  static const __attribute__((used,unused,section(PICK_SECTION_(".lua_libs",cfgname)))) \
+  const LOCK_IN_SECTION(".lua_libs") \
     luaL_Reg MODULE_PASTE_(lua_lib_,cfgname) = { luaname, initfunc }; \
-  static const __attribute__((used,unused,section(PICK_SECTION_(".lua_rotable",cfgname)))) \
-    luaR_table MODULE_PASTE_(lua_rotable_,cfgname) = { luaname, map }
+  const LOCK_IN_SECTION(".lua_rotable") \
+    luaR_table MODULE_EXPAND_PASTE_(cfgname,MODULE_EXPAND_PASTE_(_module_selected,MODULE_PASTE_(LUA_USE_MODULES_,cfgname))) \
+    = { luaname, map }
 
 
 /* System module registration support, not using LUA_USE_MODULES_XYZ. */
 #define BUILTIN_LIB_INIT(name, luaname, initfunc) \
-  static const __attribute__((used,unused,section(".lua_libs"))) \
+  const LOCK_IN_SECTION(".lua_libs") \
     luaL_Reg MODULE_PASTE_(lua_lib_,name) = { luaname, initfunc }
 
 #define BUILTIN_LIB(name, luaname, map) \
-  static const __attribute__((used,unused,section(".lua_rotable"))) \
+  const LOCK_IN_SECTION(".lua_rotable") \
     luaR_table MODULE_PASTE_(lua_rotable_,name) = { luaname, map }
 
 #if !(MIN_OPT_LEVEL==2 && LUA_OPTIMIZE_MEMORY==2)
diff --git a/ld/nodemcu.ld b/ld/nodemcu.ld
index e67e9af0..8c4ee61a 100644
--- a/ld/nodemcu.ld
+++ b/ld/nodemcu.ld
@@ -83,10 +83,10 @@ SECTIONS
     . = ALIGN(4);
     lua_libs = ABSOLUTE(.);
     /* Allow either empty define or defined-to-1 to include the module */
-    KEEP(*(.lua_libs .lua_libs1))
+    KEEP(*(.lua_libs))
     LONG(0) LONG(0) /* Null-terminate the array */
     lua_rotable = ABSOLUTE(.);
-    KEEP(*(.lua_rotable .lua_rotable1))
+    KEEP(*(.lua_rotable))
     LONG(0) LONG(0) /* Null-terminate the array */
 
     /* These are *only* pulled in by Lua, and therefore safe to put in flash */