cross compile with LLVM and sysroots

cpython-unix/build.cross-loongarch64.Dockerfile

@@ -33,13 +33,12 @@ RUN for s in debian_trixie debian_trixie-updates; do \
 
 RUN apt-get update
 
-# Host building.
+# Build tools, same as in build.Dockerfile
 RUN apt-get install \
     bzip2 \
     ca-certificates \
     curl \
-    gcc \
-    g++ \
+    file \
     libc6-dev \
     libffi-dev \
     make \
@@ -53,9 +52,16 @@ RUN apt-get install \
     zlib1g-dev
 
 RUN apt-get install \
-    g++-loongarch64-linux-gnu \
-    gcc-loongarch64-linux-gnu \
-    libc6-dev-loong64-cross
+    binutils-loongarch64-linux-gnu \
+    libc6-loong64-cross \
+    libc6-dev-loong64-cross \
+    linux-libc-dev-loong64-cross \
+    libgcc-s1-loong64-cross \
+    libgcc-14-dev-loong64-cross
+
+# Target-specific symlinks to cross-compile using the external LLVM toolchain.
+RUN ln -s /tools/llvm/bin/clang /usr/bin/loongarch64-linux-gnu-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/loongarch64-linux-gnu-clang++
 
 RUN cd /tmp && \
     curl -LO https://snapshot.debian.org/archive/debian-ports/20240812T192057Z/pool-loong64/main/libx/libxcrypt/libcrypt-dev_4.4.36-4_loong64.deb && \

cpython-unix/build.cross.Dockerfile

@@ -32,11 +32,12 @@ RUN for s in debian_stretch debian_stretch-updates debian-security_stretch/updat
 
 RUN apt-get update
 
-# Host building.
+# Build tools, same as in build.Dockerfile
 RUN apt-get install \
     bzip2 \
-    gcc \
-    g++ \
+    ca-certificates \
+    curl \
+    file \
     libc6-dev \
     libffi-dev \
     make \
@@ -49,29 +50,56 @@ RUN apt-get install \
     zip \
     zlib1g-dev
 
-# Cross-building.
+# Target sysroots and host binutils for cross-compiling with the external LLVM
+# toolchain.
 RUN apt-get install \
-    g++-aarch64-linux-gnu \
-    g++-arm-linux-gnueabi \
-    g++-arm-linux-gnueabihf \
-    g++-mips-linux-gnu \
-    g++-mips64el-linux-gnuabi64 \
-    g++-mipsel-linux-gnu \
-    g++-powerpc64le-linux-gnu \
-    g++-s390x-linux-gnu \
-    gcc-aarch64-linux-gnu \
-    gcc-arm-linux-gnueabi \
-    gcc-arm-linux-gnueabihf \
-    gcc-mips-linux-gnu \
-    gcc-mips64el-linux-gnuabi64 \
-    gcc-mipsel-linux-gnu \
-    gcc-powerpc64le-linux-gnu \
-    gcc-s390x-linux-gnu \
-    libc6-dev-arm64-cross \
+    binutils-arm-linux-gnueabi \
+    binutils-arm-linux-gnueabihf \
+    binutils-mips-linux-gnu \
+    binutils-mipsel-linux-gnu \
+    binutils-powerpc64le-linux-gnu \
+    binutils-s390x-linux-gnu \
+    libc6-armel-cross \
+    libc6-armhf-cross \
+    libc6-mips-cross \
+    libc6-mipsel-cross \
+    libc6-ppc64el-cross \
+    libc6-s390x-cross \
     libc6-dev-armel-cross \
     libc6-dev-armhf-cross \
     libc6-dev-mips-cross \
-    libc6-dev-mips64el-cross \
     libc6-dev-mipsel-cross \
     libc6-dev-ppc64el-cross \
-    libc6-dev-s390x-cross
+    libc6-dev-s390x-cross \
+    linux-libc-dev-armel-cross \
+    linux-libc-dev-armhf-cross \
+    linux-libc-dev-mips-cross \
+    linux-libc-dev-mipsel-cross \
+    linux-libc-dev-ppc64el-cross \
+    linux-libc-dev-s390x-cross \
+    libgcc1-armel-cross \
+    libgcc1-armhf-cross \
+    libgcc1-mips-cross \
+    libgcc1-mipsel-cross \
+    libgcc1-ppc64el-cross \
+    libgcc1-s390x-cross \
+    libgcc-6-dev-armel-cross \
+    libgcc-6-dev-armhf-cross \
+    libgcc-6-dev-mips-cross \
+    libgcc-6-dev-mipsel-cross \
+    libgcc-6-dev-ppc64el-cross \
+    libgcc-6-dev-s390x-cross
+
+# Target-specific symlinks to cross-compile using the external LLVM toolchain.
+RUN ln -s /tools/llvm/bin/clang /usr/bin/arm-linux-gnueabi-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/arm-linux-gnueabi-clang++ && \
+    ln -s /tools/llvm/bin/clang /usr/bin/arm-linux-gnueabihf-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/arm-linux-gnueabihf-clang++ && \
+    ln -s /tools/llvm/bin/clang /usr/bin/mips-linux-gnu-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/mips-linux-gnu-clang++ && \
+    ln -s /tools/llvm/bin/clang /usr/bin/mipsel-linux-gnu-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/mipsel-linux-gnu-clang++ && \
+    ln -s /tools/llvm/bin/clang /usr/bin/powerpc64le-linux-gnu-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/powerpc64le-linux-gnu-clang++ && \
+    ln -s /tools/llvm/bin/clang /usr/bin/s390x-linux-gnu-clang && \
+    ln -s /tools/llvm/bin/clang++ /usr/bin/s390x-linux-gnu-clang++

cpython-unix/targets.yml

@@ -180,11 +180,12 @@ armv7-unknown-linux-gnueabi:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/arm-linux-gnueabi-gcc
-  target_cxx: /usr/bin/arm-linux-gnueabi-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/arm-linux-gnueabi-clang
+  target_cxx: /usr/bin/arm-linux-gnueabi-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -224,11 +225,12 @@ armv7-unknown-linux-gnueabihf:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/arm-linux-gnueabihf-gcc
-  target_cxx: /usr/bin/arm-linux-gnueabihf-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/arm-linux-gnueabihf-clang
+  target_cxx: /usr/bin/arm-linux-gnueabihf-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -268,11 +270,12 @@ loongarch64-unknown-linux-gnu:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross-loongarch64
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/loongarch64-linux-gnu-gcc
-  target_cxx: /usr/bin/loongarch64-linux-gnu-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/loongarch64-linux-gnu-clang
+  target_cxx: /usr/bin/loongarch64-linux-gnu-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -313,11 +316,12 @@ mips-unknown-linux-gnu:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/mips-linux-gnu-gcc
-  target_cxx: /usr/bin/mips-linux-gnu-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/mips-linux-gnu-clang
+  target_cxx: /usr/bin/mips-linux-gnu-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -357,11 +361,12 @@ mipsel-unknown-linux-gnu:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/mipsel-linux-gnu-gcc
-  target_cxx: /usr/bin/mipsel-linux-gnu-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/mipsel-linux-gnu-clang
+  target_cxx: /usr/bin/mipsel-linux-gnu-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -401,11 +406,12 @@ ppc64le-unknown-linux-gnu:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/powerpc64le-linux-gnu-gcc
-  target_cxx: /usr/bin/powerpc64le-linux-gnu-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/powerpc64le-linux-gnu-clang
+  target_cxx: /usr/bin/powerpc64le-linux-gnu-clang++
   target_ldflags:
     # Hardening
     - '-Wl,-z,noexecstack'
@@ -490,11 +496,12 @@ s390x-unknown-linux-gnu:
     - '3.13'
     - '3.14'
     - '3.15'
+  needs_toolchain: true
   docker_image_suffix: .cross
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/s390x-linux-gnu-gcc
-  target_cxx: /usr/bin/s390x-linux-gnu-g++
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: /usr/bin/s390x-linux-gnu-clang
+  target_cxx: /usr/bin/s390x-linux-gnu-clang++
   target_cflags:
     # set the minimum compatibility level to z10 (released 2008)
     - '-march=z10'