Stop passing link arguments to compile-only sanity checks

mesonbuild/compilers/mixins/clike.py

@@ -282,8 +282,17 @@ def _sanity_check_compile_args(self, sourcename: str, binname: str
         # Cross-compiling is hard. For example, you might need -nostdlib, or to pass --target, etc.
         mode = CompileCheckMode.COMPILE if self.is_cross and not self.environment.has_exe_wrapper() else CompileCheckMode.LINK
         cargs, b_largs = self._get_basic_compiler_args(mode)
-        largs = self.linker_to_compiler_args(b_largs)
         s_args, s_largs = super()._sanity_check_compile_args(sourcename, binname)
+        if mode is CompileCheckMode.COMPILE:
+            # We aren't linking in this invocation (and can't run the result
+            # without an exe wrapper anyway), so don't pass any link-only
+            # arguments to a compile-only command. Some compilers add fixed
+            # flags (e.g. MSVC-style compilers always prepend /link) even
+            # when there is nothing to link, which would otherwise end up
+            # unused/misplaced in a compile-only invocation.
+            return s_args + cargs, []
+
+        largs = self.linker_to_compiler_args(b_largs)
         return s_args + cargs, s_largs + largs
 
     def check_header(self, hname: str, prefix: str, *,

unittests/internaltests.py

@@ -30,7 +30,7 @@
 import mesonbuild.scripts.env2mfile
 from mesonbuild import coredata
 from mesonbuild.compilers.c import ClangCCompiler, GnuCCompiler
-from mesonbuild.compilers.compilers import ManyInOneLinkerOptionStyle
+from mesonbuild.compilers.compilers import Compiler, ManyInOneLinkerOptionStyle
 from mesonbuild.compilers.cpp import VisualStudioCPPCompiler
 from mesonbuild.compilers.d import DmdDCompiler
 from mesonbuild.compilers.detect import detect_c_compiler
@@ -416,6 +416,25 @@ def test_compiler_args_class_visualstudio(self):
         self.assertEqual(a.to_native(copy=True), ['/showIncludes'])
 
 
+    def test_clike_sanity_check_drops_link_only_args_when_compile_only(self):
+        # When cross-compiling without an exe wrapper, CLikeCompiler's sanity
+        # check only compiles and never links because we can't run the
+        # executable. Therefore, it doesn't make sense for link-only arguments
+        # to be added on the command line. Some compilers warn about unused
+        # command line arguments.
+        env = get_fake_env()
+        linker = linkers.MoldDynamicLinker([], env, MachineChoice.HOST, '-Wl,', [])
+        cc = ClangCCompiler([], [], '14.0.0', MachineChoice.HOST, env, linker=linker)
+        cc.is_cross = True
+
+        with mock.patch.object(env, 'has_exe_wrapper', return_value=False), \
+             mock.patch.object(cc, '_get_basic_compiler_args', return_value=([], ['-fake-cross-link-arg'])), \
+             mock.patch.object(Compiler, '_sanity_check_compile_args', return_value=([], ['-Lfake-ldflags-arg'])):
+            _, largs = cc._sanity_check_compile_args('foo.c', 'foo.exe')
+
+        self.assertEqual(largs, [])
+
+
     def test_msvc_unix_args_to_native(self):
         # joined
         self.assertEqual(MSVCCompiler.unix_args_to_native(['-isystemfoo']), ['/Ifoo'])