The -all_load flag is intended to force the linker to load all lazy members, but doesn't do so if the archive is specified with --start-lib, --end-lib flags. The `-all_load` flag is global, that is it can be placed anywhere in the linker invocation, and it affects the load behavior of all conventional archives listed. Unlike ELF's --whole-archive, the user need not necessarily have access to the entire linker invocation to reasonably make use of the flag. The user can supply `-all_load` to a build system without inspecting the rest of the linker invocation.
To make the behavior of `--start-lib` style archives consistent with regular archives, this patch makes it so that -all_load also applies in this case.
In ld.lld, when an ObjFile/BitcodeFile is read in --start-lib state, the file is
given archive semantics. --end-lib closes the previous --start-lib. A build
system can use this feature as an alternative to archives. This patch ports
the feature to lld-macho.
--start-lib and --end-lib are positional, unlike usual ld64 options.
I think the slight drawback does not matter as (a) reusing option names
make build systems convenient (b) `--start-lib a.o b.o --end-lib` conveys more
information than an alternative design: `-objlib a.o -objlib b.o` because
--start-lib makes it clear which objects are in the same conceptual archive.
This provides flexibility (c) `-objlib`/`-filelist` interaction may be weird.
Close https://github.com/llvm/llvm-project/issues/52931
Reviewed By: #lld-macho, Jez Ng, oontvoo
Differential Revision: https://reviews.llvm.org/D116913
