[ELF] Keep st_type for symbol assignment
PR46970: for `alias = aliasee`, the alias can be used in relocation processing
and on ARM st_type does affect Thumb interworking. It is thus desirable for the
alias to get the same st_type.
Note that the st_size field should not be inherited because some tools use
st_size=0 as a heuristic to detect aliases. Retaining st_size can thwart such
heuristics and cause aliases to be preferred over the original symbols.
Differential Revision: https://reviews.llvm.org/D86263
diff --git a/lld/docs/ELF/linker_script.rst b/lld/docs/ELF/linker_script.rst
index 0f409b2..debddbf 100644
--- a/lld/docs/ELF/linker_script.rst
+++ b/lld/docs/ELF/linker_script.rst
@@ -17,6 +17,25 @@
it is appropriate for LLD. Intentional deviations will be documented in this
file.
+Symbol assignment
+~~~~~~~~~~~~~~~~~
+
+A symbol assignment looks like:
+
+::
+
+ symbol = expression;
+ symbol += expression;
+
+The first form defines ``symbol``. If ``symbol`` is already defined, it will be
+overridden. The other form requires ``symbol`` to be already defined.
+
+For a simple assignment like ``alias = aliasee;``, the ``st_type`` field is
+copied from the original symbol. Any arithmetic operation (e.g. ``+ 0`` will
+reset ``st_type`` to ``STT_NOTYPE``.
+
+The ``st_size`` field is set to 0.
+
Output section description
~~~~~~~~~~~~~~~~~~~~~~~~~~
