Q: Weak symbol defaulting to an other symbol?

[Georg-Johann Lay]

In an assembler module, I would like to introduce a weak symbol like in:

     .weak my_symbol
     my_symbol = __heap_start
     ;; use my_symbol...

where __heap_start is defined in the linker script as

     PROVIDE (__heap_start = .)

The code will be part of a static library.

The generated code when linking against the static lib is as
expected.  Though what doesn't work is to let the user adjust
my_symbol when they don't like the default, e.g. by
     --defsym my_symbol=0x12324
or by code like

     .global my_symbol
     my_symbol = 0x12345

in some module.

Binutils version is 2.45.  So I already found out that overriding
the default doesn't work, and that's likely on purpose.

In order to get a better understanding, I'd like to ask why this
doesn't work, and what's the thinko in my intended design? Having
a user-adjustable symbol that defaults to some symbol value seems
to be a useful feature.


Johann