List of standard / common symbols used in the linker script

Hi @All,

while I was focusing understanding and writing my linker script & startup files for my Cortex M3 MCU (Spansion MB9BF510R-Series), I recognized that somehow there seems to be common confusion about the existing symbols used.
It looks like there is just a lot of copy and paste going around.

So my question is, is there a list of of standard / common symbols (especially ones other libraries might use or expect) ?

some example: You can find a lot of different implementations of the bss section

a) here (from the CMSIS gcc_arm.ld) it is __bss_start__ and __bss_end__ --> OK !

.bss :
{
  . = ALIGN(4);
  __bss_start__ = .;
  *(.bss*)
  *(COMMON)
  . = ALIGN(4);
  __bss_end__ = .;
} > RAM

b) This one uses _sbss, __sbss, _ebss, __ebss (each 2 symbols with the sam VMA) --> WHY??

.bss : ALIGN(4)
 {
  . = ALIGN(4);
  _sbss = .;
  __sbss = _sbss;
  *(.bss*)
  *(COMMON)
  . = ALIGN(4);
  _ebss = .;
  __ebss = _ebss ;
} > RAM

c) This one defines _end & __end (where both are the same) --> WHY??

.bss : ALIGN (8)
{
  *(.shbss)
  *(.bss .bss.* .gnu.linkonce.b.*)
  *(COMMON)
  . = ALIGN (8);
  *(.ram.b .bss.ram)
  . = ALIGN (8);
  _end = .;
  __end = .;
} >ram

d) No underscores used / sbss & ebss outside of section definition

sbss = .;
.bss : { * (.bss); }
 ebss = .;
 bss_size = ebss - sbss;

e) ONLY declaration of a heap section I found mentioning about the common used symbol ("end = ." for newlib)

. = ALIGN(4);
    .heap :
    {
        __end__ = .;
        /* _heap_start = .; */
        /* "end" is used by newlib's syscalls!!! */
        PROVIDE(end = .);
        PROVIDE(_heap_start = end );
        . = . + heap_size;
        PROVIDE(_heap_end = .);
    } >RAM

In addition I'd like to know if there is any priority in usage of the symbols.
Cause one I found in a startup_*.S this:

 .section .heap , "w" /* w = section is writable */
 .align 3
#ifdef __HEAP_SIZE__
 .equ __HeapSize, __HEAP_SIZE__
#else
 .equ __HeapSize, 0x00000400
#endif
 .globl __HeapStart
 .globl __HeapEnd
    .globl __HeapSize
__HeapStart:
 .if __HeapSize
 .space __HeapSize
 .endif
__HeapEnd:

and in the linker script

.heap
{
   . = ALIGN(4) ;
   _sheap = .;
   *(.heap*);
    . = ALIGN(4) ;
   _eheap = .;
}
PROVIDE(__HeapStart = _sheap);
PROVIDE(__HeapEnd = _eheap);
PROVIDE(__HeapSize = SIZEOF(.heap));

so which symbol definition is overridden? The __HeapSize from the asm or __HeapSize from the indirection file?