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.
esp8266 · Jan 17, 2018 · e7d98a4 · e7d98a4
1 parent 074402e
commit e7d98a4
Showing 1 changed file with 67 additions and 66 deletions.
diff --git 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(.);