add @zig_sdk//:<os>_<arch>_platform values

README.md

@@ -130,24 +130,8 @@ The path to Bazel toolchains is `@zig_sdk//:<toolchain>_toolchain`. It should
 be moved to `@zig_sdk//toolchain:<toolchain>` or similar; so the user-facing
 targets are in their own namespace.
 
-Currently, platform is not defined in `@zig_sdk`. As you may see in the
+Likewise, platforms are `@zig_sdk//:<platform>_platform`, and should be moved
-examples, we are currently using the one provided by cgo. E.g.
+to `@zig_sdk//:platform:<platform>`.
-`@io_bazel_rules_go//go/toolchain:linux_amd64_cgo`. This is because we want to
-define it in `@zig_sdk//:platform:<platform>`. This is waiting for mine or a
-contributor's attention. You may work around this by sending a patch to
-bazel-zig-cc or specifying the platform in your project:
-
-```
-platform(
-    name = "linux_aarch64",
-    constraint_values = [
-        "@bazel_tools//platforms:linux",
-        "@bazel_tools//platforms:aarch64",
-    ]
-)
-```
-
-and `--platforms="//:linux_aarch64"`.
 
 # Known Issues In Upstream
 
@@ -184,7 +168,7 @@ may apply to aarch64, but the author didn't find a need to test it (yet).
 ## linux cgo + glibc 2.28
 
 ```
-$ bazel build --platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo //test:hello
+$ bazel build --platforms @zig_sdk//:linux_amd64_platform //test:hello
 $ file bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello
 bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.0.0, Go BuildID=redacted, with debug_info, not stripped
 ```
@@ -193,7 +177,7 @@ bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello: ELF 64-bit LSB exe
 
 ```
 $ bazel build \
-    --platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo \
+    --platforms @zig_sdk//:linux_amd64_platform \
     --extra_toolchains @zig_sdk//:linux_amd64_musl_toolchain //test:hello
 ...
 $ file ../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello
@@ -205,7 +189,7 @@ hello, world
 ## macos cgo
 
 ```
-$ bazel build --platforms @io_bazel_rules_go//go/toolchain:darwin_amd64_cgo //test:hello
+$ bazel build --platforms @zig_sdk//:darwin_amd64_platform //test:hello
 ...
 $ file bazel-bin/test/hello_/hello
 bazel-bin/test/hello_/hello: Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>

ci/test

@@ -30,28 +30,28 @@ _test "Host" \
 
 _test "darwin_amd64" \
   "Mach-O 64-bit x86_64 executable" \
-    --platforms @io_bazel_rules_go//go/toolchain:darwin_amd64_cgo
+    --platforms @zig_sdk//:darwin_amd64_platform
 
 # hello world on darwin/arm64 requires OSX SDK via `zig cc --sysroot=<...>`.
 # see https://github.com/ziglang/zig/issues/10299#issuecomment-989595215
 #_test "darwin_arm64" \
 #    "Mach-O 64-bit arm64 executable" \
-#    --platforms @io_bazel_rules_go//go/toolchain:darwin_arm64_cgo
+#    --platforms @zig_sdk//:darwin_arm64_platform
 
 _test "linux_amd64_gnu" \
     "ELF 64-bit.* x86-64.* dynamically linked" \
-    --platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo
+    --platforms @zig_sdk//:linux_amd64_platform
 
 _test "linux_amd64_musl" \
     "ELF 64-bit.* x86-64.* statically linked" \
-    --platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo \
+    --platforms @zig_sdk//:linux_amd64_platform \
     --extra_toolchains @zig_sdk//:linux_amd64_musl_toolchain
 
 _test "linux_arm64_gnu" \
     "ELF 64-bit.* ARM aarch64.* dynamically linked" \
-    --platforms @io_bazel_rules_go//go/toolchain:linux_arm64_cgo
+    --platforms @zig_sdk//:linux_arm64_platform
 
 _test "linux_arm64_musl" \
     "ELF 64-bit.* ARM aarch64.* statically linked" \
-    --platforms @io_bazel_rules_go//go/toolchain:linux_arm64_cgo \
+    --platforms @zig_sdk//:linux_arm64_platform \
     --extra_toolchains @zig_sdk//:linux_arm64_musl_toolchain

toolchain/defs.bzl

@@ -376,3 +376,20 @@ def zig_build_macro(absolute_path, zig_include_root):
             toolchain = ":%s_toolchain_cc" % zigtarget,
             toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
         )
+
+    # create @zig_sdk//{os}_{arch}_platform entries with zig and go conventions
+    for zigcpu, gocpu in (("x86_64", "amd64"), ("aarch64", "arm64")):
+        for bzlos, oss in {"linux": ["linux"], "macos": ["macos", "darwin"]}.items():
+            for os in oss:
+                constraint_values = [
+                    "@platforms//os:{}".format(bzlos),
+                    "@platforms//cpu:{}".format(zigcpu),
+                ]
+                native.platform(
+                    name = "{os}_{zigcpu}_platform".format(os = os, zigcpu = zigcpu),
+                    constraint_values = constraint_values,
+                )
+                native.platform(
+                    name = "{os}_{gocpu}_platform".format(os = os, gocpu = gocpu),
+                    constraint_values = constraint_values,
+                )