From e7d98a420162d63da65d0f1c8e25227c80cfbf17 Mon Sep 17 00:00:00 2001
From: "Earle F. Philhower, III" <earlephilhower@yahoo.com>
Date: Tue, 16 Jan 2018 19:35:45 -0800
Subject: [PATCH] Move C++ vtables into IRAM, out of HEAP

GCC places vtables in .rodata, with a mangled name of "_ZTV*."  Because
these are simply address jump tables, there is no need to place them in
RAM.  Instead, have the linker place them in the .text (aka IRAM) section.
This will free up a variable amount of heap space, depending on the number
of classes with virtual functions used in any particular project.
---
 tools/sdk/ld/eagle.app.v6.common.ld | 133 ++++++++++++++--------------
 1 file changed, 67 insertions(+), 66 deletions(-)

diff --git a/tools/sdk/ld/eagle.app.v6.common.ld b/tools/sdk/ld/eagle.app.v6.common.ld
index c61741ab0e..c9993c7bba 100644
--- a/tools/sdk/ld/eagle.app.v6.common.ld
+++ b/tools/sdk/ld/eagle.app.v6.common.ld
@@ -84,72 +84,6 @@ SECTIONS
     _data_end = ABSOLUTE(.);
   } >dram0_0_seg :dram0_0_phdr
 
-  .rodata : ALIGN(4)
-  {
-    _rodata_start = ABSOLUTE(.);
-    *(.sdk.version)
-    *(.rodata)
-    *(.rodata.*)
-    *(.gnu.linkonce.r.*)
-    *(.rodata1)
-    __XT_EXCEPTION_TABLE__ = ABSOLUTE(.);
-    *(.xt_except_table)
-    *(.gcc_except_table)
-    *(.gnu.linkonce.e.*)
-    *(.gnu.version_r)
-    *(.eh_frame)
-    . = (. + 3) & ~ 3;
-    /*  C++ constructor and destructor tables, properly ordered:  */
-    __init_array_start = ABSOLUTE(.);
-    KEEP (*crtbegin.o(.ctors))
-    KEEP (*(EXCLUDE_FILE (*crtend.o) .ctors))
-    KEEP (*(SORT(.ctors.*)))
-    KEEP (*(.ctors))
-    __init_array_end = ABSOLUTE(.);
-    KEEP (*crtbegin.o(.dtors))
-    KEEP (*(EXCLUDE_FILE (*crtend.o) .dtors))
-    KEEP (*(SORT(.dtors.*)))
-    KEEP (*(.dtors))
-    /*  C++ exception handlers table:  */
-    __XT_EXCEPTION_DESCS__ = ABSOLUTE(.);
-    *(.xt_except_desc)
-    *(.gnu.linkonce.h.*)
-    __XT_EXCEPTION_DESCS_END__ = ABSOLUTE(.);
-    *(.xt_except_desc_end)
-    *(.dynamic)
-    *(.gnu.version_d)
-    . = ALIGN(4);       /* this table MUST be 4-byte aligned */
-    _bss_table_start = ABSOLUTE(.);
-    LONG(_bss_start)
-    LONG(_bss_end)
-    _bss_table_end = ABSOLUTE(.);
-    _rodata_end = ABSOLUTE(.);
-  } >dram0_0_seg :dram0_0_phdr
-
-  .bss ALIGN(8) (NOLOAD) : ALIGN(4)
-  {
-    . = ALIGN (8);
-    _bss_start = ABSOLUTE(.);
-    *(.dynsbss)
-    *(.sbss)
-    *(.sbss.*)
-    *(.gnu.linkonce.sb.*)
-    *(.scommon)
-    *(.sbss2)
-    *(.sbss2.*)
-    *(.gnu.linkonce.sb2.*)
-    *(.dynbss)
-    *(.bss)
-    *(.bss.*)
-    *(.gnu.linkonce.b.*)
-    *(COMMON)
-    . = ALIGN (8);
-    _bss_end = ABSOLUTE(.);
-    _heap_start = ABSOLUTE(.);
-/*    _stack_sentry = ALIGN(0x8); */
-  } >dram0_0_seg :dram0_0_bss_phdr
-/* __stack = 0x3ffc8000; */
-
   .irom0.text : ALIGN(4)
   {
     _irom0_text_start = ABSOLUTE(.);
@@ -231,6 +165,7 @@ SECTIONS
     *(.literal .text .literal.* .text.* .stub .gnu.warning .gnu.linkonce.literal.* .gnu.linkonce.t.*.literal .gnu.linkonce.t.*)
     *.cpp.o(.iram.text)
     *.c.o(.iram.text)
+    *(.rodata._ZTV*) /* C++ vtables */
     /* PlatformIO */
     /* framework */
     *.pioenvs\\*\\lib*.a:(.iram.text)
@@ -249,6 +184,72 @@ SECTIONS
     _etext = .;
   } >iram1_0_seg :iram1_0_phdr
 
+  .rodata : ALIGN(4)
+  {
+    _rodata_start = ABSOLUTE(.);
+    *(.sdk.version)
+    *(.rodata)
+    *(.rodata.*)
+    *(.gnu.linkonce.r.*)
+    *(.rodata1)
+    __XT_EXCEPTION_TABLE__ = ABSOLUTE(.);
+    *(.xt_except_table)
+    *(.gcc_except_table)
+    *(.gnu.linkonce.e.*)
+    *(.gnu.version_r)
+    *(.eh_frame)
+    . = (. + 3) & ~ 3;
+    /*  C++ constructor and destructor tables, properly ordered:  */
+    __init_array_start = ABSOLUTE(.);
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+    __init_array_end = ABSOLUTE(.);
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+    /*  C++ exception handlers table:  */
+    __XT_EXCEPTION_DESCS__ = ABSOLUTE(.);
+    *(.xt_except_desc)
+    *(.gnu.linkonce.h.*)
+    __XT_EXCEPTION_DESCS_END__ = ABSOLUTE(.);
+    *(.xt_except_desc_end)
+    *(.dynamic)
+    *(.gnu.version_d)
+    . = ALIGN(4);       /* this table MUST be 4-byte aligned */
+    _bss_table_start = ABSOLUTE(.);
+    LONG(_bss_start)
+    LONG(_bss_end)
+    _bss_table_end = ABSOLUTE(.);
+    _rodata_end = ABSOLUTE(.);
+  } >dram0_0_seg :dram0_0_phdr
+
+  .bss ALIGN(8) (NOLOAD) : ALIGN(4)
+  {
+    . = ALIGN (8);
+    _bss_start = ABSOLUTE(.);
+    *(.dynsbss)
+    *(.sbss)
+    *(.sbss.*)
+    *(.gnu.linkonce.sb.*)
+    *(.scommon)
+    *(.sbss2)
+    *(.sbss2.*)
+    *(.gnu.linkonce.sb2.*)
+    *(.dynbss)
+    *(.bss)
+    *(.bss.*)
+    *(.gnu.linkonce.b.*)
+    *(COMMON)
+    . = ALIGN (8);
+    _bss_end = ABSOLUTE(.);
+    _heap_start = ABSOLUTE(.);
+/*    _stack_sentry = ALIGN(0x8); */
+  } >dram0_0_seg :dram0_0_bss_phdr
+/* __stack = 0x3ffc8000; */
+
   .lit4 : ALIGN(4)
   {
     _lit4_start = ABSOLUTE(.);