[WIP] Fix compile error with wchar_t in System.Globalization.Native

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Problem

Building on a recent macOS / Xcode toolchain (clang 20+) fails when compiling System.Globalization.Native:

In file included from src/native/libs/System.Globalization.Native/pal_idna.c:7:
In file included from src/native/libs/System.Globalization.Native/pal_icushim_internal.h:47:
/opt/homebrew/opt/icu4c/include/unicode/ustring.h:1203:8: error: identifier 'wchar_t' conflicts with a C++ keyword [-Werror,-Wc++-keyword]
 1203 | U_CAPI wchar_t* U_EXPORT2

Repro: ./build.sh clr -c Release --cross -a x64 on macOS arm64.

Newer clang added the -Wc++-keyword diagnostic. Because this native lib is built with -Weverything -Werror, the Homebrew ICU header's use of wchar_t becomes a hard error.

Requested fix

Satori is a fork of dotnet/runtime, so please cherry-pick the corresponding upstream dotnet/runtime commit(s) rather than hand-writing the change, so future merges from upstream stay clean.

1. Locate the upstream dotnet/runtime commit that added add_compile_options(-Wno-c++-keyword) to src/native/libs/System.Globalization.Native/CMakeLists.txt (in the "Workaround for warnings produced by ICU headers" block). In current dotnet/runtime main the file looks like:

    # Workaround for warnings produced by ICU headers
    add_compile_options(-Wno-reserved-id-macro)
    add_compile_options(-Wno-documentation)
    add_compile_options(-Wno-documentation-unknown-command)
    add_compile_options(-Wno-reserved-identifier)
    add_compile_options(-Wno-c++-keyword)

You can add dotnet/runtime as a remote (git remote add upstream https://github.com/dotnet/runtime.git, fetch, then git log -S"-Wno-c++-keyword" -- src/native/libs/System.Globalization.Native/CMakeLists.txt) and git cherry-pick -x <sha> the relevant commit(s), resolving conflicts minimally.

2. If network access to upstream is unavailable, or the cherry-pick is not cleanly applicable, fall back to applying the equivalent minimal edit yourself: add add_compile_options(-Wno-c++-keyword) to the ICU header workaround block in src/native/libs/System.Globalization.Native/CMakeLists.txt (Satori currently lacks this line). Note -Wno-unknown-warning-option is already set nearby, so older clangs are unaffected.

3. Also check whether upstream applied the same suppression anywhere else that Satori is missing (e.g. src/native/libs/CMakeLists.txt), and include it only if needed.

Keep the change as small as possible. Mention the cherry-picked upstream SHA(s) in the PR description, or state explicitly if you had to fall back to a manual edit.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: I am building the PR bits with a command: ./build.sh clr -c Release --cross -a x64

it has been a long time since I built this repo. There was couple OS updates since then.

In file included from /Users/vs/Satori/Satori/src/native/libs/System.Globalization.Native/pal_idna.c:7:
In file included from /Users/vs/Satori/Satori/src/native/libs/System.Globalization.Native/pal_icushim_internal.h:47:
/opt/homebrew/opt/icu4c/include/unicode/ustring.h:1203:8: error: identifier 'wchar_t' conflicts with a C++ keyword [-Werror,-Wc++-keyword]
1203 | U_CAPI wchar_t* U_EXPORT2
| ^
/opt/homebrew/opt/icu4c/include/unicode/ustring.h:1204:12: error: identifier 'wchar_t' conflicts with a C++ keyword [-Werror,-Wc++-keyword]
1204 | u_strToWCS(wchar_t *dest,
| ^
/opt/homebrew/opt/icu4c/include/unicode/ustring.h:1236:20: error: identifier 'wchar_t' conflicts with a C++ keyword [-Werror,-Wc++-keyword]
1236 | const wchar_t *src,
| ^
I am getting compile errors:

Assistant: This is unrelated to PR #83 — it's a newer-Xcode/clang issue. Clang 20+ added -Wc++-keyword, and since System.Globalization.Native builds with -Weverything -Werror, the Homebrew ICU header's use of wchar_t now fails.

Upstream dotnet/runtime already fixed this by suppressing that warning in the globalization CMakeLists (it currently only lives in the wasm branch of src/native/libs/CMakeLists.txt in your tree). Apply the same one-liner:

     # Workaround for warnings produced by ICU headers
     add_compile_options(-Wno-reserved-id-macro)
     add_compile_options(-Wno-documentation)
     add_compile_options(-Wno-documentation-unknown-command)
     add_compile_options(-Wno-reserved-identifier)
+    add_compile_options(-Wno-c++-keyword)
 
     # Workaround for https://unicode-org.atlassian.net/browse/ICU-20601
     add_compile_options(-Wno-extra-semi-stmt)
     add_compile_options(-Wno-unknown-warning-option)

-Wno-unknown-warning-option is already there, so older clangs that don't know -Wc++-keyword won't complain.

Alternatives if you'd rather not touch the build: downgrade/pin an older Homebrew icu4c (the wchar_t decls in ustring.h are what trip it), or select an older Xcode via xcode-select. The CMake change is the cleaner, upstream-aligned fix.

Want me to open a PR with this change?

User: lets open a PR. ideally we would cherry pick the commits, so we could easier merge from upstream

Assistant: I've queued up the coding agent task to cherry-pick the upstream -Wno-c++-keyword fix — just waiting on your confirmation of the dialog to kick it off.

[VSadov]

@copilot are there actual file changes?