Merge pull request #11924 from dcbaker/submit/c++stdlib-fixes

Do a better job of detecting libc++ vs libstdc++

mesonbuild/compilers/cpp.py

@@ -183,7 +183,48 @@ class CPPCompiler(CLikeCompiler, Compiler):
         return opts
 
 
-class ClangCPPCompiler(ClangCompiler, CPPCompiler):
+class _StdCPPLibMixin(CompilerMixinBase):
+
+    """Detect whether to use libc++ or libstdc++."""
+
+    @functools.lru_cache(None)
+    def language_stdlib_only_link_flags(self, env: Environment) -> T.List[str]:
+        """Detect the C++ stdlib and default search dirs
+
+        As an optimization, this method will cache the value, to avoid building the same values over and over
+
+        :param env: An Environment object
+        :raises MesonException: If a stdlib cannot be determined
+        """
+
+        # We need to apply the search prefix here, as these link arguments may
+        # be passed to a different compiler with a different set of default
+        # search paths, such as when using Clang for C/C++ and gfortran for
+        # fortran.
+        search_dirs = [f'-L{d}' for d in self.get_compiler_dirs(env, 'libraries')]
+
+        machine = env.machines[self.for_machine]
+        assert machine is not None, 'for mypy'
+
+        # We need to determine whether to us libc++ or libstdc++ In some cases
+        # we know the answer, so we'll hardcode those cases.  There are other
+        # cases where we can't know the answer just by looking at the OS, namely
+        # on Linux. In that case we have to fallback to manually checking
+        stdlib: str
+        if machine.system in {'android', 'darwin', 'dragonfly', 'freebsd', 'netbsd', 'openbsd'}:
+            stdlib = 'c++'
+        elif self.find_library('c++', env, []) is not None:
+            stdlib = 'c++'
+        elif self.find_library('stdc++', env, []) is not None:
+            stdlib = 'stdc++'
+        else:
+            # TODO: maybe a bug exception?
+            raise MesonException('Could not detect either libc++ or libstdc++ as your C++ stdlib implementation.')
+
+        return search_dirs + [f'-l{stdlib}']
+
+
+class ClangCPPCompiler(_StdCPPLibMixin, ClangCompiler, CPPCompiler):
     def __init__(self, ccache: T.List[str], exelist: T.List[str], version: str, for_machine: MachineChoice, is_cross: bool,
                  info: 'MachineInfo', exe_wrapper: T.Optional['ExternalProgram'] = None,
                  linker: T.Optional['DynamicLinker'] = None,
@@ -249,16 +290,6 @@ class ClangCPPCompiler(ClangCompiler, CPPCompiler):
             return libs
         return []
 
-    def language_stdlib_only_link_flags(self, env: 'Environment') -> T.List[str]:
-        # We need to apply the search prefix here, as these link arguments may
-        # be passed to a different compiler with a different set of default
-        # search paths, such as when using Clang for C/C++ and gfortran for
-        # fortran,
-        search_dirs: T.List[str] = []
-        for d in self.get_compiler_dirs(env, 'libraries'):
-            search_dirs.append(f'-L{d}')
-        return search_dirs + ['-lstdc++']
-
 
 class ArmLtdClangCPPCompiler(ClangCPPCompiler):
 
@@ -266,15 +297,7 @@ class ArmLtdClangCPPCompiler(ClangCPPCompiler):
 
 
 class AppleClangCPPCompiler(ClangCPPCompiler):
-    def language_stdlib_only_link_flags(self, env: 'Environment') -> T.List[str]:
-        # We need to apply the search prefix here, as these link arguments may
-        # be passed to a different compiler with a different set of default
-        # search paths, such as when using Clang for C/C++ and gfortran for
-        # fortran,
-        search_dirs: T.List[str] = []
-        for d in self.get_compiler_dirs(env, 'libraries'):
-            search_dirs.append(f'-L{d}')
-        return search_dirs + ['-lc++']
+    pass
 
 
 class EmscriptenCPPCompiler(EmscriptenMixin, ClangCPPCompiler):
@@ -353,7 +376,7 @@ class ArmclangCPPCompiler(ArmclangCompiler, CPPCompiler):
         return []
 
 
-class GnuCPPCompiler(GnuCompiler, CPPCompiler):
+class GnuCPPCompiler(_StdCPPLibMixin, GnuCompiler, CPPCompiler):
     def __init__(self, ccache: T.List[str], exelist: T.List[str], version: str, for_machine: MachineChoice, is_cross: bool,
                  info: 'MachineInfo', exe_wrapper: T.Optional['ExternalProgram'] = None,
                  linker: T.Optional['DynamicLinker'] = None,
@@ -434,16 +457,6 @@ class GnuCPPCompiler(GnuCompiler, CPPCompiler):
     def get_pch_use_args(self, pch_dir: str, header: str) -> T.List[str]:
         return ['-fpch-preprocess', '-include', os.path.basename(header)]
 
-    def language_stdlib_only_link_flags(self, env: 'Environment') -> T.List[str]:
-        # We need to apply the search prefix here, as these link arguments may
-        # be passed to a different compiler with a different set of default
-        # search paths, such as when using Clang for C/C++ and gfortran for
-        # fortran,
-        search_dirs: T.List[str] = []
-        for d in self.get_compiler_dirs(env, 'libraries'):
-            search_dirs.append(f'-L{d}')
-        return ['-lstdc++']
-
 
 class PGICPPCompiler(PGICompiler, CPPCompiler):
     def __init__(self, ccache: T.List[str], exelist: T.List[str], version: str, for_machine: MachineChoice, is_cross: bool,