From 17bf98c01cd6ffc0cd1a1c48ade28ed0a01ffad0 Mon Sep 17 00:00:00 2001
From: "Earle F. Philhower, III" <earlephilhower@yahoo.com>
Date: Fri, 23 Mar 2018 07:25:52 -0700
Subject: [PATCH] g_cont to unused space in SYS, gives extra 4K free

Use a linker option to hardcode the address of the g_cont context
variable to in a region of RAM allocated for SYS use but which is not
presently used.

Gives an additional 4K+ of heap to all apps.
---
 cores/esp8266/core_esp8266_main.cpp | 2 +-
 tools/sdk/ld/eagle.app.v6.common.ld | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/cores/esp8266/core_esp8266_main.cpp b/cores/esp8266/core_esp8266_main.cpp
index cb7401366e..40e96c8ea5 100644
--- a/cores/esp8266/core_esp8266_main.cpp
+++ b/cores/esp8266/core_esp8266_main.cpp
@@ -76,7 +76,7 @@ void preloop_update_frequency() {
 extern void (*__init_array_start)(void);
 extern void (*__init_array_end)(void);
 
-cont_t g_cont __attribute__ ((aligned (16)));
+cont_t __attribute__ ((section(".sys_unused"))) g_cont __attribute__ ((aligned (16)));
 static os_event_t g_loop_queue[LOOP_QUEUE_SIZE];
 
 static uint32_t g_micros_at_task_start;
diff --git a/tools/sdk/ld/eagle.app.v6.common.ld b/tools/sdk/ld/eagle.app.v6.common.ld
index cbc1ebf871..8da9e19b9b 100644
--- a/tools/sdk/ld/eagle.app.v6.common.ld
+++ b/tools/sdk/ld/eagle.app.v6.common.ld
@@ -162,6 +162,11 @@ SECTIONS
     _etext = .;
   } >iram1_0_seg :iram1_0_phdr
 
+  .sys_unused_data 0x3fffe000 :
+  {
+    *(.sys_unused)
+  }
+
   .rodata : ALIGN(4)
   {
     _rodata_start = ABSOLUTE(.);