Early adoption of new technologies or adjusting certain code generation/IR optimization thresholds
is often available through some cl::opt options (which have unstable surfaces).
Specifying such an option twice will lead to an error.
```
% clang -c a.c -mllvm -disable-binop-extract-shuffle -mllvm -disable-binop-extract-shuffle
clang (LLVM option parsing): for the --disable-binop-extract-shuffle option: may only occur zero or one times!
% clang -c a.c -mllvm -hwasan-instrument-reads=0 -mllvm -hwasan-instrument-reads=0
clang (LLVM option parsing): for the --hwasan-instrument-reads option: may only occur zero or one times!
% clang -c a.c -mllvm --scalar-evolution-max-arith-depth=32 -mllvm --scalar-evolution-max-arith-depth=16
clang (LLVM option parsing): for the --scalar-evolution-max-arith-depth option: may only occur zero or one times!
```
The option is specified twice, because there is sometimes a global setting and
a specific file or project may need to override (or duplicately specify) the
value.
The error is contrary to the common practice of getopt/getopt_long command line
utilities that let the last option win and the `getLastArg` behavior used by
Clang driver options. I have seen such errors for several times. I think the
error just makes users inconvenient, while providing very little value on
discouraging production usage of unstable surfaces (this goal is itself
controversial, because developers might not want to commit to a stable surface
too early, or there is just some subtle codegen toggle which is infeasible to
have a driver option). Therefore, I suggest we drop the diagnostic, at least
before the diagnostic gets sufficiently better support for the overridding needs.
Removing the error is a degraded error checking experience. I think this error
checking behavior, if desirable, should be enabled explicitly by tools. Users
preferring the behavior can figure out a way to do so.
Reviewed By: jhenderson, rnk
Differential Revision: https://reviews.llvm.org/D120455
libtool can currently produce 2 warnings:
1. No symbols were in the object file
2. An object file with the same basename was specified multiple times
The first warning here is often harmless and may just mean you have some
translation units with no symbols for the target you're building for.
The second warning can lead to real issues like those mentioned in
https://reviews.llvm.org/D113130 where ODR violations can slip in.
This introduces a new -warnings_as_errors flag that can be used by build
systems that want to verify they never hit these warnings. For example
with bazel the libtool caller first uniques names to make sure the
duplicate base name case is not possible, but if that doesn't work as
expected, having it fail would be preferred.
It's also worth noting that llvm-libtool-darwin works around an issue
that cctools libtool experiences related to debug info and duplicate
basenames, the workaround is described here:
30baa5d2a4/llvm/lib/Object/ArchiveWriter.cpp (L424-L465)
And it avoids this bug:
f0cbbb1c37/DuplicateBasenameIssue
Differential Revision: https://reviews.llvm.org/D118931
Print a warning if `llvm-libtool-darwin` if any of the object
files provided by the user have the same file name.
The tool will now print a warning if there is a name collision across:
* Two object files
* An object file and an object file from within a static library
* Two object files from different static libraries
Here is an example of the error:
```
$ llvm-libtool-darwin -static -o archive.a out.o out.o
error: file 'out.o' was specified multiple times.
in: out.o
in: out.o
$ llvm-libtool-darwin -static -o archive.a out.o
$ llvm-libtool-darwin -static -o combined.a archive.a out.o
error: file 'out.o' was specified multiple times.
in: archive.a
in: out.o
```
This change mimics apple's cctools libtool's behavior which always shows a warning in such cases.
Reviewed By: smeenai
Differential Revision: https://reviews.llvm.org/D113130
This diff adds support for LLVM bitcode objects to llvm-libtool-darwin.
Test plan: make check-all
Differential revision: https://reviews.llvm.org/D88722
Add support for creating static libraries when the input includes only
Mach-O binaries (and not libraries/archives themselves).
Reviewed by alexshap, Ktwu, smeenai, jhenderson, MaskRay, mtrent
Differential Revision: https://reviews.llvm.org/D83002
Fangrui Song