name: Set up a musl Rust target
description: Install the stable toolchain for a static Linux musl target, with the C toolchain and the link shims aws-lc-sys needs.
inputs:
  target:
    description: x86_64-unknown-linux-musl or aarch64-unknown-linux-musl
    required: true
runs:
  using: composite
  steps:
    - name: Install Rust toolchain
      uses: dtolnay/rust-toolchain@stable
      with:
        targets: ${{ inputs.target }}

    - name: Install musl tools (amd64)
      if: inputs.target == 'x86_64-unknown-linux-musl'
      shell: bash
      run: |
        sudo apt-get install -y musl-tools
        # C deps (aws-lc-sys) must compile against musl headers, not the host
        # gcc's glibc headers — glibc's C23 redirects (__isoc23_sscanf,
        # __isoc23_strtol) don't exist in musl and fail the link.
        echo "CC_x86_64_unknown_linux_musl=musl-gcc" >> "$GITHUB_ENV"

    - name: Install cross-compilation tools (arm64)
      if: inputs.target == 'aarch64-unknown-linux-musl'
      shell: bash
      run: |
        sudo apt-get install -y gcc-aarch64-linux-gnu
        echo "CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL_LINKER=aarch64-linux-gnu-gcc" >> "$GITHUB_ENV"
        # Disable glibc fortify source — its __memcpy_chk etc. symbols don't exist in musl
        echo "CFLAGS_aarch64_unknown_linux_musl=-U_FORTIFY_SOURCE" >> "$GITHUB_ENV"
        # aws-lc-sys compiles against glibc headers, which redirect
        # sscanf/strtol to C23 __isoc23_* symbols musl does not provide.
        # Link a tiny forwarding shim so those references resolve to the
        # musl implementations. Prototypes are declared manually: including
        # glibc headers here would re-redirect the calls back to __isoc23_*.
        cat > /tmp/isoc23-shim.c <<'SHIM'
        #include <stdarg.h>
        extern int vsscanf(const char *s, const char *fmt, va_list ap);
        extern long strtol(const char *nptr, char **endptr, int base);
        int __isoc23_sscanf(const char *s, const char *fmt, ...) {
            va_list ap;
            va_start(ap, fmt);
            int r = vsscanf(s, fmt, ap);
            va_end(ap);
            return r;
        }
        long __isoc23_strtol(const char *nptr, char **endptr, int base) {
            return strtol(nptr, endptr, base);
        }
        SHIM
        aarch64-linux-gnu-gcc -O2 -c /tmp/isoc23-shim.c -o /tmp/isoc23-shim.o
        # link-args land after libc on the link line; rescan musl libc so
        # the shim's own vsscanf/strtol references resolve, and libgcc for
        # the fp128 builtins musl's vfscanf/floatscan pull in on aarch64.
        echo "CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL_RUSTFLAGS=-Clink-arg=/tmp/isoc23-shim.o -Clink-arg=-lc -Clink-arg=-lgcc" >> "$GITHUB_ENV"