[AutotoolsToolchain] Improve Android cross-compilation UX

conan/tools/gnu/autotoolstoolchain.py

@@ -8,7 +8,7 @@
 from conan.tools.build.cross_building import cross_building
 from conan.tools.build.flags import architecture_flag, build_type_flags, cppstd_flag, \
     build_type_link_flags, libcxx_flags, cstd_flag
-from conan.tools.env import Environment
+from conan.tools.env import Environment, VirtualBuildEnv
 from conan.tools.gnu.get_gnu_triplet import _get_gnu_triplet
 from conan.tools.microsoft import VCVars, msvc_runtime_flag, unix_path, check_min_vs, is_msvc
 from conans.model.pkg_type import PackageType
@@ -69,10 +69,8 @@ def __init__(self, conanfile, namespace=None, prefix="/"):
             # If cross-building and tools.android:ndk_path is defined, let's try to guess the Android
             # cross-building flags
             self.android_cross_flags = self._resolve_android_cross_compilation()
-            # Host triplet
-            if self.android_cross_flags:
-                self._host = self.android_cross_flags.pop("host")
-            elif not self._host:
+            # If it's not defined the triplet
+            if not self._host:
                 os_host = conanfile.settings.get_safe("os")
                 arch_host = conanfile.settings.get_safe("arch")
                 self._host = _get_gnu_triplet(os_host, arch_host, compiler=compiler)["triplet"]
@@ -109,12 +107,26 @@ def _resolve_android_cross_compilation(self):
         ret = {}
         if not self._is_cross_building or not self._conanfile.settings.get_safe("os") == "Android":
             return ret
+        # User variables have more priority than Conan ones
+        build_env = VirtualBuildEnv(self._conanfile, auto_generate=True).vars()
+        for var in ["CC", "CXX", "LD", "STRIP", "RANLIB", "AS", "AR", "ADDR2LINE", "NM", "OBJCOPY",
+                    "OBJDUMP", "READELF", "ELFEDIT", "host"]:
+            if build_env.get(var) is not None:
+                ret[var] = build_env[var]
+
+        arch = self._conanfile.settings.get_safe("arch")
+        android_target = {'armv7': 'armv7a-linux-androideabi',
+                          'armv8': 'aarch64-linux-android',
+                          'x86': 'i686-linux-android',
+                          'x86_64': 'x86_64-linux-android'}.get(arch)
+        # Setting host if it was not already defined yet
+        self._host = self._host or android_target
+        # Automatic guessing made by Conan (need the NDK path variable defined)
         ndk_path = self._conanfile.conf.get("tools.android:ndk_path", check_type=str)
         if ndk_path:
             if self._conanfile.conf.get("tools.build:compiler_executables"):
                 self._conanfile.output.warning("tools.build:compiler_executables conf has no effect"
                                                " when tools.android:ndk_path is defined too.")
-            arch = self._conanfile.settings.get_safe("arch")
             os_build = self._conanfile.settings_build.get_safe("os")
             ndk_os_folder = {
                 'Macos': 'darwin',
@@ -131,22 +143,31 @@ def _resolve_android_cross_compilation(self):
             ndk_bin = os.path.join(ndk_path, "toolchains", "llvm", "prebuilt",
                                    f"{ndk_os_folder}-x86_64", "bin")
             android_api_level = self._conanfile.settings.get_safe("os.api_level")
-            android_target = {'armv7': 'armv7a-linux-androideabi',
-                              'armv8': 'aarch64-linux-android',
-                              'x86': 'i686-linux-android',
-                              'x86_64': 'x86_64-linux-android'}.get(arch)
             os_build = self._conanfile.settings_build.get_safe('os')
             ext = ".cmd" if os_build == "Windows" else ""
-            ret = {
+            conan_vars = {
                 "CC": os.path.join(ndk_bin, f"{android_target}{android_api_level}-clang{ext}"),
                 "CXX": os.path.join(ndk_bin, f"{android_target}{android_api_level}-clang++{ext}"),
                 "LD": os.path.join(ndk_bin, "ld"),
                 "STRIP": os.path.join(ndk_bin, "llvm-strip"),
                 "RANLIB": os.path.join(ndk_bin, "llvm-ranlib"),
                 "AS": os.path.join(ndk_bin, f"{android_target}{android_api_level}-clang{ext}"),
                 "AR": os.path.join(ndk_bin, "llvm-ar"),
-                "host": android_target
+                "ADDR2LINE": os.path.join(ndk_bin, "llvm-addr2line"),
+                "NM": os.path.join(ndk_bin, "llvm-nm"),
+                "OBJCOPY": os.path.join(ndk_bin, "llvm-objcopy"),
+                "OBJDUMP": os.path.join(ndk_bin, "llvm-objdump"),
+                "READELF": os.path.join(ndk_bin, "llvm-readelf"),
+                "ELFEDIT": os.path.join(ndk_bin, "llvm-elfedit")
             }
+            build_env = VirtualBuildEnv(self._conanfile, auto_generate=True).vars()
+            for var in conan_vars:
+                # User variables have more priority than Conan ones
+                if build_env.get(var) is not None:
+                    ret[var] = build_env[var]
+                # Do not take into account any deduced file if it does not exist
+                elif os.path.exists(conan_vars[var]):
+                    ret.setdefault(var, conan_vars[var])
         return ret
 
     def _get_msvc_runtime_flag(self):
@@ -162,7 +183,7 @@ def _msvc_extra_flags(self):
         return []
 
     def _add_msvc_flags(self, flags):
-        # This is to avoid potential duplicate with users recipes -FS (alreday some in ConanCenter)
+        # This is to avoid potential duplicate with users recipes -FS (already some in ConanCenter)
         return [f for f in self.msvc_extra_flags if f not in flags]
 
     @staticmethod

conan/tools/meson/toolchain.py

@@ -412,6 +412,7 @@ def _resolve_android_cross_compilation(self):
                           'x86_64': 'x86_64-linux-android'}.get(arch)
         os_build = self._conanfile.settings_build.get_safe('os')
         compiler_extension = ".cmd" if os_build == "Windows" else ""
+        # User has more prio than Conan
         self.c = os.path.join(ndk_bin, "{}{}-clang{}".format(android_target, android_api_level, compiler_extension))
         self.cpp = os.path.join(ndk_bin, "{}{}-clang++{}".format(android_target, android_api_level, compiler_extension))
         self.ar = os.path.join(ndk_bin, "llvm-ar")

test/unittests/client/toolchain/autotools/autotools_toolchain_test.py

@@ -1,20 +1,22 @@
+import os
 import platform
-from os import chdir
+from unittest.mock import patch, MagicMock
 
 import pytest
 
-from conan.tools.build import load_toolchain_args
-from conan.tools.gnu import AutotoolsToolchain
 from conan.errors import ConanException
-from conans.model.conf import Conf
 from conan.test.utils.mocks import ConanFileMock, MockSettings, MockOptions
 from conan.test.utils.test_files import temp_folder
+from conan.tools.build import load_toolchain_args
+from conan.tools.files import save
+from conan.tools.gnu import AutotoolsToolchain
+from conans.model.conf import Conf
 
 
 def test_modify_environment():
     """We can alter the environment generated by the toolchain passing the env to the generate"""
     f = temp_folder()
-    chdir(f)
+    os.chdir(f)
     conanfile = ConanFileMock()
     conanfile.settings = MockSettings({"os": "Linux", "arch": "x86_64"})
     conanfile.settings_build = MockSettings({"os": "Solaris", "arch": "x86"})
@@ -31,7 +33,7 @@ def test_modify_environment():
 
 def test_target_triple():
     f = temp_folder()
-    chdir(f)
+    os.chdir(f)
     conanfile = ConanFileMock()
     conanfile.settings = MockSettings({"os": "Linux", "arch": "x86_64"})
     conanfile.settings_build = MockSettings({"os": "Solaris", "arch": "x86"})
@@ -356,6 +358,7 @@ def test_apple_min_os_flag():
     assert expected in env["LDFLAGS"]
 
 
+@patch("conan.tools.gnu.autotoolstoolchain.VirtualBuildEnv", new=MagicMock(vars={}))
 def test_crossbuild_from_macos_to_non_apple_os():
     """Check we are not adding Apple-specific flags
         when the os_build is Macos, but we are targetting
@@ -369,6 +372,40 @@ def test_crossbuild_from_macos_to_non_apple_os():
     assert be.apple_isysroot_flag is None
 
 
+@patch("conan.tools.gnu.autotoolstoolchain.VirtualBuildEnv")
+def test_crossbuild_to_android(build_env_mock):
+    """
+    Issue related: https://github.com/conan-io/conan/issues/17441
+    """
+    vars = MagicMock()
+    vars.vars.return_value = {"CC": "my-clang", "CXX": "my-clang++"}
+    build_env_mock.return_value = vars
+
+    conanfile = ConanFileMock()
+    conanfile.settings = MockSettings({"os": "Android", "arch": "armv8"})
+    conanfile.settings_build = MockSettings({"os": "Macos", "arch": "armv8"})
+    at = AutotoolsToolchain(conanfile)
+    env_vars = at.vars()
+    assert env_vars["CC"] == "my-clang"
+    assert env_vars["CXX"] == "my-clang++"
+    assert at._host == "aarch64-linux-android"
+    assert env_vars.get("LD") is None
+    assert env_vars.get("STRIP") is None
+
+    # Defining the ndk_path too
+    ndk_path = temp_folder()
+    ld_file = os.path.join(ndk_path, "toolchains", "llvm", "prebuilt", "darwin-x86_64", "bin", "ld")
+    save(conanfile, ld_file, "")
+    conanfile.conf.define("tools.android:ndk_path", ndk_path)
+    at = AutotoolsToolchain(conanfile)
+    env_vars = at.vars()
+    assert env_vars["CC"] == "my-clang"
+    assert env_vars["CXX"] == "my-clang++"
+    assert at._host == "aarch64-linux-android"
+    assert env_vars["LD"] == ld_file  # exists
+    assert env_vars.get("STRIP") is None
+
+
 def test_apple_isysrootflag():
     """Even when no cross building it is adjusted because it could target a Mac version"""
     conanfile = ConanFileMock()