Problem here is if zig is asked to create multiple static libraries, it
will build the runtime multiple times and then they will conflict.
Instead we want to build the runtime exactly once.
Unlike `compiler-rt`, `ubsan` uses the standard library quite a lot.
Using a similar approach to how `compiler-rt` is handled today, where it's
compiled into its own object and then linked would be sub-optimal as we'd
be introducing a lot of code bloat.
This approach always "imports" `ubsan` if the ZCU, if it exists. If it doesn't
such as the case where we're compiling only C code, then we have no choice other
than to compile it down to an object and link. There's still a tiny optimization
we can do in that case, which is when compiling to a static library, there's no
need to construct an archive with a single object. We'd only go back and parse out
ubsan from the archive later in the pipeline. So we compile it to an object instead
and link that to the static library.
TLDR;
- `zig build-exe foo.c` -> build `libubsan.a` and links
- `zig build-obj foo.c` -> doesn't build anything, just emits references to ubsan runtime
- `zig build-lib foo.c -static` -> build `ubsan.o` and link it
- `zig build-exe foo.zig bar.c` -> import `ubsan-rt` into the ZCU
- `zig build-obj foo.zig bar.c` -> import `ubsan-rt` into the ZCU
- `zig build-lib foo.zig bar.c` -> import `ubsan-rt` into the ZCU
Instead of hardcoding a call to defaultRandomSeed() use the customizable
std.options.cryptoRandomSeed() like in the rest of the function.
Closes#19943.
In #22522 I said:
> RC="zig rc" will now work in combination with zig cc and CMake. Here's an example of cross-compiling a simple Windows GUI CMake project
>
> $ RC="zig rc" CC="zig cc --target=x86_64-windows-gnu" cmake .. -DCMAKE_SYSTEM_NAME=Windows -G Ninja
However, I didn't realize that the time that this only works because of the `-G Ninja` part. When not using Ninja as the build tool, CMake adds a workaround for 'very long lists of object files' where it takes all object files and runs them through `ar` to combine them into one archive:
4a11fd8dde/Modules/Platform/Windows-GNU.cmake (L141-L158)
This is a problem for the Windows resource use-case, because `ar` doesn't know how to deal with `.res` files and so this object combining step fails with:
unknown file type: foo.rc.res
Only the linker knows what to do with .res files (since it has its own `.res` -> `.obj` ('cvtres') conversion mechanism). So, when using Ninja, this object file combining step is skipped and the .res file gets passed to the linker and everyone is happy.
Note: When CMake thinks that its using `windres` as the Windows resource compiler, it will pass `-O coff` to windres which causes it to output a COFF object file instead of a `.res` file, which means that the `ar` step can succeed because it's only working on actual object files.
---
This commit gives `zig rc` the ability to output COFF object files directly when `/:output-format coff` is provided as an argument. This effectively matches what happens when CMake uses `windres` for resource compilation, but requires the argument to be provided explicitly.
So, after this change, the following CMake cross-compilation use case will work, even when not using Ninja as the generator:
RC="zig rc /:output-format coff" CC="zig cc --target=x86_64-windows-gnu" cmake .. -DCMAKE_SYSTEM_NAME=Windows
