From 903ae13d643c305c48c4271ed4a05939656ed041 Mon Sep 17 00:00:00 2001
From: "Lauren N. Liberda" <lauren@selfisekai.rocks>
Date: Sat, 8 Apr 2023 02:56:35 +0200
Subject: [PATCH 1/2] add gn args specifying libc for linux

---
 build/config/compiler/BUILD.gn         |  8 ++-
 build/config/linux/detect_host_libc.py | 42 ++++++++++++
 build/config/linux/libc.gni            | 51 +++++++++++++++
 build/toolchain/linux/BUILD.gn         | 89 ++++++++++++++------------
 4 files changed, 147 insertions(+), 43 deletions(-)
 create mode 100755 build/config/linux/detect_host_libc.py
 create mode 100644 build/config/linux/libc.gni

diff --git a/engine/src/build/config/compiler/BUILD.gn b/engine/src/build/config/compiler/BUILD.gn
index 4c9a1ee..155d433 100644
--- ./engine/src/build/config/compiler/BUILD.gn.orig
+++ ./engine/src/build/config/compiler/BUILD.gn
@@ -12,6 +12,9 @@
 if (is_win) {
   import("//build/config/win/visual_studio_version.gni")
 }
+if (is_linux) {
+  import("//build/config/linux/libc.gni")
+}
 
 import("//build/config/c++/c++.gni")
 import("//build/config/profiler.gni")
@@ -339,8 +342,8 @@
     ldflags += [ "-pthread" ]
 
     if (current_cpu == "arm64") {
-      cflags += [ "--target=aarch64-linux-gnu" ]
-      ldflags += [ "--target=aarch64-linux-gnu" ]
+      cflags += [ "--target=aarch64-alpine-linux-musl" ]
+      ldflags += [ "--target=aarch64-alpine-linux-musl" ]
       cflags += [ "-DBORINGSSL_CLANG_SUPPORTS_DOT_ARCH" ]
     }
   }
@@ -622,12 +625,15 @@
   default_warning_flags += [
     # Enables.
     "-Wendif-labels",  # Weird old-style text after an #endif.
-    "-Werror",  # Warnings as errors.
 
     # Disables.
     "-Wno-missing-field-initializers",  # "struct foo f = {0};"
     "-Wno-unused-parameter",  # Unused function parameters.
   ]
+  if (!is_linux || is_glibc) {
+    # Warnings as errors. Fails on musl.
+    default_warning_flags += [ "-Werror" ]
+  }
 
   if (is_wasm) {
     default_warning_flags += [
diff --git a/engine/src/build/config/linux/detect_host_libc.py b/engine/src/build/config/linux/detect_host_libc.py
new file mode 100755
index 0000000..1ebb498
--- /dev/null
+++ b/engine/src/build/config/linux/detect_host_libc.py
@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from optparse import OptionParser
+import re
+import subprocess
+import sys
+
+
+def main():
+    if 'linux' not in sys.platform:
+        return 1
+
+    parser = OptionParser()
+    parser.add_option('--compiler-path', action='store',
+                      type='string', default='gcc')
+    (options, args) = parser.parse_args()
+
+    # should work with both gcc and clang
+    #
+    # example outputs: "aarch64-unknown-linux-gnu", "x86_64-alpine-linux-musl",
+    # "armv7-unknown-linux-musleabihf", "mipsel-linux-muslhf"
+    default_target = subprocess.check_output([
+        options.compiler_path, '-dumpmachine']).decode('utf-8').strip()
+
+    host_libc_re = re.match(
+        r'^(?:[^-]+-){1,2}linux-(?P<libc>gnu|musl|uclibc)(?:eabi)?(?:hf)?$',
+        default_target)
+    if host_libc_re is None:
+        print(f'Target not understood: {default_target}')
+
+    host_libc = host_libc_re.group('libc')
+    # print would add a newline
+    sys.stdout.write(host_libc)
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/engine/src/build/config/linux/libc.gni b/engine/src/build/config/linux/libc.gni
new file mode 100644
index 0000000..653f312
--- /dev/null
+++ b/engine/src/build/config/linux/libc.gni
@@ -0,0 +1,51 @@
+# Copyright (c) 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/sysroot.gni")
+
+declare_args() {
+  # The C library used by the compilation host.
+  # Expecting one of: "gnu" (glibc), "uclibc", "musl"
+  host_libc = ""
+
+  # The C library of the compilation target.
+  # Expecting one of: "gnu" (glibc), "uclibc", "musl"
+  target_libc = ""
+}
+
+# try to detect host's libc if not explicitly provided
+if (host_libc == "" && is_linux) {
+  if (sysroot == "") {
+    host_compiler = "gcc"
+    if (is_clang) {
+      host_compiler = "clang"
+    }
+
+    # tries to determine libc from "gcc/clang -printmachine"
+    host_libc = exec_script("//build/config/linux/detect_host_libc.py",
+                            [
+                              "--compiler-path",
+                              host_compiler,
+                            ],
+                            "string")
+  } else {
+    # currently there is only debian sysroot
+    host_libc = "gnu"
+  }
+}
+
+assert(!is_linux || host_libc != "", "Host libc not specified and not detected")
+
+# assume compiling for host if not explicitly specified
+if (target_libc == "") {
+  target_libc = host_libc
+}
+
+is_cross_libc = host_libc != target_libc
+
+is_glibc = target_libc == "gnu"
+is_musl = target_libc == "musl"
+
+is_host_glibc = host_libc == "gnu"
+is_host_musl = host_libc == "musl"
diff --git a/engine/src/build/toolchain/linux/BUILD.gn b/engine/src/build/toolchain/linux/BUILD.gn
index 05630d0..b1288ce 100644
--- a/engine/src/build/toolchain/linux/BUILD.gn
+++ b/engine/src/build/toolchain/linux/BUILD.gn
@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/linux/libc.gni")
 import("//build/config/sysroot.gni")
 import("//build/toolchain/ccache.gni")
 import("//build/toolchain/gcc_toolchain.gni")
@@ -33,16 +34,10 @@
   link_prefix = ""
 }
 
-if (host_cpu == "arm64") {
-  rebased_clang_dir =
-      rebase_path("$buildtools_path/linux-arm64/clang/bin", root_build_dir)
-} else {
-  rebased_clang_dir =
-      rebase_path("$buildtools_path/linux-x64/clang/bin", root_build_dir)
-}
+rebased_clang_dir = ""
 
 gcc_toolchain("arm") {
-  prefix = "arm-linux-gnueabihf-"
+  prefix = "arm-linux-${target_libc}eabihf-"
   if (toolchain_prefix != "") {
     prefix = toolchain_prefix
   }
@@ -64,15 +59,15 @@
 
 gcc_toolchain("clang_arm") {
   prefix = rebased_clang_dir
-  asm = "${prefix}/clang"
-  cc = "${compiler_prefix}${prefix}/clang"
-  cxx = "${compiler_prefix}${prefix}/clang++"
+  asm = "${prefix}clang"
+  cc = "${compiler_prefix}${prefix}clang"
+  cxx = "${compiler_prefix}${prefix}clang++"
 
-  readelf = "${prefix}/llvm-readelf"
-  nm = "${prefix}/llvm-nm"
-  ar = "${prefix}/llvm-ar"
-  ld = "${link_prefix}${prefix}/clang++"
-  llvm_objcopy = "${prefix}/llvm-objcopy"
+  readelf = "${prefix}llvm-readelf"
+  nm = "${prefix}llvm-nm"
+  ar = "${prefix}llvm-ar"
+  ld = "${link_prefix}${prefix}clang++"
+  llvm_objcopy = "${prefix}llvm-objcopy"
 
   toolchain_cpu = "arm"
   toolchain_os = "linux"
@@ -80,7 +75,7 @@
 }
 
 gcc_toolchain("arm64") {
-  prefix = "aarch64-linux-gnu-"
+  prefix = "aarch64-linux-${target_libc}-"
   if (toolchain_prefix != "") {
     prefix = toolchain_prefix
   }
@@ -102,15 +97,15 @@
 
 gcc_toolchain("clang_arm64") {
   prefix = rebased_clang_dir
-  asm = "${prefix}/clang"
-  cc = "${compiler_prefix}${prefix}/clang"
-  cxx = "${compiler_prefix}${prefix}/clang++"
+  asm = "${prefix}clang"
+  cc = "${compiler_prefix}${prefix}clang"
+  cxx = "${compiler_prefix}${prefix}clang++"
 
   readelf = "readelf"
-  nm = "${prefix}/llvm-nm"
-  ar = "${prefix}/llvm-ar"
-  ld = "${link_prefix}${prefix}/clang++"
-  llvm_objcopy = "${prefix}/llvm-objcopy"
+  nm = "${prefix}llvm-nm"
+  ar = "${prefix}llvm-ar"
+  ld = "${link_prefix}${prefix}clang++"
+  llvm_objcopy = "${prefix}llvm-objcopy"
 
   toolchain_cpu = "arm64"
   toolchain_os = "linux"
@@ -119,15 +114,15 @@
 
 gcc_toolchain("clang_x86") {
   prefix = rebased_clang_dir
-  asm = "${prefix}/clang"
-  cc = "${compiler_prefix}${prefix}/clang"
-  cxx = "${compiler_prefix}${prefix}/clang++"
+  asm = "${prefix}clang"
+  cc = "${compiler_prefix}${prefix}clang"
+  cxx = "${compiler_prefix}${prefix}clang++"
 
-  readelf = "${prefix}/llvm-readelf"
-  nm = "${prefix}/llvm-nm"
-  ar = "${prefix}/llvm-ar"
-  ld = "${link_prefix}${prefix}/clang++"
-  llvm_objcopy = "${prefix}/llvm-objcopy"
+  readelf = "${prefix}llvm-readelf"
+  nm = "${prefix}llvm-nm"
+  ar = "${prefix}llvm-ar"
+  ld = "${link_prefix}${prefix}clang++"
+  llvm_objcopy = "${prefix}llvm-objcopy"
 
   toolchain_cpu = "x86"
   toolchain_os = "linux"
@@ -153,15 +148,15 @@
 
 gcc_toolchain("clang_x64") {
   prefix = rebased_clang_dir
-  asm = "${prefix}/clang"
-  cc = "${compiler_prefix}${prefix}/clang"
-  cxx = "${compiler_prefix}${prefix}/clang++"
+  asm = "${prefix}clang"
+  cc = "${compiler_prefix}${prefix}clang"
+  cxx = "${compiler_prefix}${prefix}clang++"
 
-  readelf = "${prefix}/llvm-readelf"
-  nm = "${prefix}/llvm-nm"
-  ar = "${prefix}/llvm-ar"
-  ld = "${link_prefix}${prefix}/clang++"
-  llvm_objcopy = "${prefix}/llvm-objcopy"
+  readelf = "${prefix}llvm-readelf"
+  nm = "${prefix}llvm-nm"
+  ar = "${prefix}llvm-ar"
+  ld = "${link_prefix}${prefix}clang++"
+  llvm_objcopy = "${prefix}llvm-objcopy"
 
   toolchain_cpu = "x64"
   toolchain_os = "linux"
@@ -186,7 +181,7 @@
 }
 
 gcc_toolchain("riscv32") {
-  prefix = "riscv32-linux-gnu-"
+  prefix = "riscv32-linux-${target_libc}-"
   if (toolchain_prefix != "") {
     prefix = toolchain_prefix
   }
@@ -224,7 +219,7 @@
 }
 
 gcc_toolchain("riscv64") {
-  prefix = "riscv64-linux-gnu-"
+  prefix = "riscv64-linux-${target_libc}-"
   if (toolchain_prefix != "") {
     prefix = toolchain_prefix
   }
@@ -246,15 +241,15 @@
 
 gcc_toolchain("clang_riscv64") {
   prefix = rebased_clang_dir
-  asm = "${prefix}/clang"
-  cc = "${compiler_prefix}${prefix}/clang"
-  cxx = "${compiler_prefix}${prefix}/clang++"
+  asm = "${prefix}clang"
+  cc = "${compiler_prefix}${prefix}clang"
+  cxx = "${compiler_prefix}${prefix}clang++"
 
   readelf = "readelf"
-  nm = "${prefix}/llvm-nm"
-  ar = "${prefix}/llvm-ar"
-  ld = "${link_prefix}${prefix}/clang++"
-  llvm_objcopy = "${prefix}/llvm-objcopy"
+  nm = "${prefix}llvm-nm"
+  ar = "${prefix}llvm-ar"
+  ld = "${link_prefix}${prefix}clang++"
+  llvm_objcopy = "${prefix}llvm-objcopy"
 
   toolchain_cpu = "riscv64"
   toolchain_os = "linux"