lib.exe by default exits successfully without writing an output
file when no inputs are passed. llvm-lib has the same behavior,
for compatibility.
This behavior interacts poorly with build systems: If a static
library target had no inputs, llvm-lib would not produce an output
file, causing ninja (or make, or a similar system) to successfully
run that step, but then re-run it on the next build.
After this patch, llvm-lib emits a warning in this case, that with
/WX can be turned into an error. That way, ninja (or make, or...)
will mark the initial build as failed.
People who don't like the warning can use /ignore:emptyoutput to
suppress it.
The warning also points out the existing flag /llvmlibempty which
forces creation of an empty .lib file (this is an extension to lib.exe).
Differential Revision: https://reviews.llvm.org/D123517
Summary:
Add a new option (/llvmlibempty). If passed and llvm-lib does not give an error, it will create a valid output archive even if empty.
By default, llvm-lib mimicks lib.exe: if given no input files, it doesn't create its output file at all. This is incompatible with some build systems, so we add a command-line option to toggle this compatibility behavior.
Reviewed By: thakis
Differential Revision: https://reviews.llvm.org/D78894
Similarly to SVN r317189 for llvm-dlltool, these are probably
easier to find in a tools subdirectory with a name identical to
the tool, than in a toplevel directory with a different name.
This matches the move of LibDriver itself in SVN r302995.
Differential Revision: https://reviews.llvm.org/D39531
llvm-svn: 317262
Nico Weber