The active contributors and maintainers of Zig's linker code have
generally found the current linker test harness to be cumbersome. The
tests require a lot of maintenance, but do not provide a lot of
coverage, and when they fail it is painful to troubleshoot.
Furthermore, as part of working on #31691, I don't want to port over the
CheckObject step, because I don't like the code anyway.
The plan forward is to start enhancing `zig objdump` to assist in
linker development, as well as using it as the basis for snapshot
testing.
We absolutely need linker test coverage, but we need to try to improve
these things about the next attempt:
* less effort to create and maintain tests
* less CPU overhead - we should be able to add a lot of tests without
adding a lot of CI time.
* more helpful failures. A failed linker test should provide the next
steps a developer can take to understand why the test failed.
* a goal of porting over all of LLD's test suite, or at least the good
ones.
I'm not going to open an issue to track the lost linker test coverage,
because there was already so much lack of coverage for linker stuff.
However I will open issues to track this lost coverage:
* the deleted checks from test/standalone/glibc_compat/build.zig
* the deleted checks from test/standalone/compiler_rt_panic/build.zig
* the deleted checks from test/standalone/ios/build.zig
Before:
* test-zigc: run libzigc unit tests (part of test-modules)
* test-libc: run libc-test cases
Now:
* test-libc: run libc API unit tests (part of test-modules)
* test-libc-nsz: run libc-test cases
libc API unit tests (previously referred to as libzigc unit tests) now run for
all supported targets, even those we don't provide libzigc for. The idea is that
this will help us catch bad assumptions in the unit tests, as well as bugs in
other libcs.
I considered this setup:
* test-c: run libc API unit tests (part of test-modules)
* test-libc-nsz: run libc-test cases
* test-libc: both of the above
However, I do not like it because it gives a false sense of security; the full
module and C ABI test suites are still liable to catch libzigc bugs that test-c
and test-libc-nsz might not. So contributors should just run the test steps
outlined in https://codeberg.org/ziglang/zig/issues/30978.
Co-authored-by: rpkak <rpkak@noreply.codeberg.org>
This number should never be raised. If the value is exceeded, then it is
considered a bug in the Zig project that building the compiler takes
more than 8G of memory.
Partial revert of 1293f080fd
Deprioritizes #31510
These functions can only be exported when external libc components are
available due to the errno location dependency. Note that even when zig
libc is complete, on Windows, errno location will always be external (in
ucrtbase.dll).
It has been observed in practice on powerpc64(le)-linux that zig.o (in various
stages and build modes) is large enough that the +/- 32MB branch range of
PowerPC is insufficient to reach from one end of the code section to the other.
With LLVM 21, this leads to silent miscompiles that then crash at runtime. With
LLVM 22, it will at least lead to branch range errors that fail the compilation,
but that gets us no closer to a working compiler.
By using these options, we give the linker much greater flexibility to move code
and data around to satisfy these range constraints; without them, the linker is
not allowed to split up the huge code and data sections of zig.o to do so.
Similar issues have also been observed on powerpc-linux (32-bit), hexagon-linux,
and some variations of mips(64)(el)-linux. But let's be conservative for now;
those other targets can be added to the condition later.
As a data point to support this change, it's worth noting that LLD started
enabling these options for LTO precisely because the resulting large compilation
units ran into these range issues. In some abstract sense, Zig can be seen as
doing a limited form of "LTO" in the frontend, so it's not surprising that we
would hit the same issues.
error: memory usage peaked at 6.05GB (6047436800 bytes), exceeding the
declared upper bound of 6.04GB (6044158771 bytes)
This value isn't meant to be OS-specific anyway.
this gets the build runner compiling again on linux
this work is incomplete; it only moves code around so that environment
variables can be wrangled properly. a future commit will need to audit
the cancelation and error handling of this moved logic.
Alex Rønne Petersen