Until now we needed to maintain two versions of the zig launcher: one
for Windows and one for everything else. This was problematic for two
reasons:
1. I do not know powershell and thus keep breaking the Windows wrapper
all the time (see git history of Fabian fixing stuff that I broke).
2. This makes bazel-zig-cc dependent on the system shell, making it not
really hermetic. So the recently added
`--experimental_use_hermetic_linux_sandbox` does not work with
bazel-zig-cc, unless we bind-mount a bunch of stuff: `/usr`, `/bin`,
`/lib`, `/usr/lib:/lib`, `/usr/lib64:/lib64` and `/proc`.
Switching to a Zig-based wrapper solves both issues, and we can do this:
bazel build "$@" \
--experimental_use_hermetic_linux_sandbox \
--sandbox_add_mount_pair=/proc \
<...>
Zig itself still depends on `/proc` for `/proc/self/exe`, so we need to
keep that. I will look into reducing even that dependency separately.
Not all is nice and shiny though: this commit replaces ~80 LOC worth of
shell scripts wrappers with a singe ~300 LOC zig program, which is
arguably harder to understand. However, it is easier to change, at least
for me, because it's a single file with unit tests! Most importantly,
the gnarly code (which resolves paths and sets environment variables) is
cross-platform.
Thanks to Fabian Hahn for testing this on Windows and pointing out
errors.
On macos, dynamic libraries are generated as "libfoo.dylib".
On windows, executables end with ".exe", static libraries end with ".lib",
and dynamic libraries end with ".dll".
We already know which headers are necessary, so it's wasteful to put the
full zig_sdk to every sandbox.
This reduces the number of files in `external/zig_sdk` from 15k to 4k or
6k, depending on the action.
Go ignores CFLAGS for some commands. That causes unnecessary build of
glibc shims (and libc++.a).
In the GCC days cross-compiler toolchains used to expose a "tool" per
architecture. Let's do the same here. Then Go cannot cheat with skipping
CFLAGS which we normally *always* expect.
The wrapper code is getting gnarly, I know. But it still fits in my head
somehow, so we can still keep adding to it.
Empirically these need to come from most specfic to least specific.
The error message is as follows:
In file included from test/c/main.c:1:
In file included from external/zig_sdk/lib/libcxx/include/stdio.h:107:
In file included from external/zig_sdk/lib/libc/include/generic-glibc/stdio.h:38:
external/zig_sdk/lib/libc/include/generic-glibc/bits/types.h:139:3: error:
# error
^
external/zig_sdk/lib/libc/include/generic-glibc/bits/types.h:145:1: error: unknown type name '__STD_TYPE'
__STD_TYPE __DEV_T_TYPE __dev_t; /* Type of device numbers. */
Dissected `generic-glibc/bits/types.h:#error`:
#if __WORDSIZE == 32
<...>
# define __STD_TYPE __extension__ typedef
#elif __WORDSIZE == 64
<...>
# define __STD_TYPE typedef
#else
# error
#endif
So we do not have the `__WORDSIZE`. Where does that come from? Probably from a
directory that has an `x86_64` in it. How does that get included? Let's start
with `lib/libcxx/include/stdio.h`:
16 #include_next <stdio.h>
Now previously our `c++` command line looked like this:
external/zig_sdk/tools/c++ \
<...>
-Iexternal/zig_sdk/lib/include \
-Iexternal/zig_sdk/lib/libcxx/include \
-Iexternal/zig_sdk/lib/libcxxabi/include \
-Iexternal/zig_sdk/lib/libunwind/include \
-Iexternal/zig_sdk/lib/libc/include/generic-glibc \
-Iexternal/zig_sdk/lib/libc/include/any-linux-any \
-Iexternal/zig_sdk/lib/libc/include/x86_64-linux-gnu \
-Iexternal/zig_sdk/lib/libc/include/x86_64-linux-any \
-Iexternal/zig_sdk/lib/libc/include/x86-linux-any \
-Iexternal/zig_sdk/glibc-hacks \
<...>
So the next place it will find `stdio.h` is in `generic-glibc`, which already
uses the `__WORDSIZE`. If we make the "next" include to be the arch-specific
one instead of the generic-glibc, things start compiling again.
Fix the same fo musl.
These flags were added in this commit:
commit 58a04fbfec
Author: Motiejus Jakštys <motiejus@jakstys.lt>
Date: Tue Jun 15 09:10:15 2021 +0300
bump zig
I am still quite puzzled on why I did this and in such a commit: it
bumps the zig version and changes the linker flag.
Working alone, experimentation time? Probably something like this.
Anyhow, this is a good example of the real value of code reviews.
While integrating the project into our Bazel workspace, we had some
problems while building protoc in an Intel MacBook.
From my testing, the issue seems to be caused by missing include path
in the toolchain configuration to the `-none` variant of the headers.
More details below.
The issue can be reproduced directly inside `bazel-zig-cc` by including
the protobuf workspace as a dependency:
+http_archive(
+ name = "com_google_protobuf",
+ sha256 = "2d9084d3dd13b86ca2e811d2331f780eb86f6d7cb02b405426e3c80dcbfabf25",
+ strip_prefix = "protobuf-3.21.1",
+ url = "https://github.com/protocolbuffers/protobuf/archive/v3.21.1.zip",
+)
+
+load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
+
+protobuf_deps()
And then executing:
bazel build --platforms @zig_sdk//platform:darwin_amd64 @com_google_protobuf//:protoc
The command fails with the same error both in native compilation and
cross-compiling from Linux. The error:
ERROR: <output_base>/external/zlib/BUILD.bazel:37:11: Compiling compress.c failed: undeclared inclusion(s) in rule '@zlib//:zlib':
this rule is missing dependency declarations for the following files included by 'compress.c':
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/cdefs.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_symbol_aliasing.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/machine/limits.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/i386/limits.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/i386/_limits.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/syslimits.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/machine/types.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/i386/types.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/i386/_types.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_types/_int8_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_types/_uintptr_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/machine/_types.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_types.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/machine/endian.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/i386/endian.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/libkern/_OSByteOrder.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/libkern/i386/_OSByteOrder.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_types/_fd_def.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/Availability.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/AvailabilityInternal.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_attr_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_cond_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_condattr_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_rwlock_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_rwlockattr_t.h'
'<output_base>/external/zig_sdk/lib/libc/include/x86_64-macos.10-none/sys/_pthread/_pthread_t.h'
Target @com_google_protobuf//:protoc failed to build
(<output_base> replaced manually to keep the description sane)
Note that the specific rule included in the error message will vary due
to parallelism, but the error is always the same and the missing paths
always have the same prefix (up to `x86_64-macos.10-none`).
After applying the patch, we confirmed that both native and cross compilations
works as expected and can properly build protoc.
Signed-off-by: Luis Holanda <luiscmholanda@gmail.com>
This linker flag causes undefined symbols to be ignored, which is the
default behavior on linux but not macos. This is required when building
shared libraries to use as e.g. Python modules. This also matches what
Bazel's built-in macos cc toolchain does.
