[llvm-dev] lld: ELF/COFF main() interface

[Arseny Kapoulkine via llvm-dev]

In the process of migrating from old lld ELF linker to new (previously
ELF2) I noticed the interface lost several important features (ordered by
importance for my use case):

1. Detecting errors in the first place. New linker seems to call exit(1)
for any error.

2. Reporting messages to non-stderr outputs. Previously all link functions
had a raw_ostream argument so it was possible to delay the error output,
aggregate it for multiple linked files, output via a different format, etc.

3. Linking multiple outputs in parallel (useful for test drivers) in a
single process. Not really an interface issue but there are at least two
global pointers (Config & Driver) that refer to stack variables and are
used in various places in the code.

All of this seems to indicate a departure from the linker being useable as
a library. To maintain the previous behavior you'd have to use a linker
binary & popen.

Is this a conscious design decision or a temporary limitation?

If it's a limitation, how would one go about fixing this? I'm not too
familiar with the idiomatical error handling in LLVM. Normally in this
situation I'd just throw from error() but lld is probably compiled without
exceptions. Is ErrorOr the established practice? How does LLVM generally
deal with error handling for parsers (like linker script parser) where it's
a lot of mutually recursive functions where every single one can fail?

Arseny
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160107/09a9ef49/attachment.html>