More linker wrapper improvements (#381)

* Updated linker to always require a compiler (previously it was actually never checked if the wrapped compiler actually exists, it only checked the linker).

* Remove unreliable test, since there is no guarantee that a C linker is returned, see issue #379.

* Fixed bug that a wrapper would not report openmp status based on the compiler.

* Added more description for this test.

source/fab/tools/compiler.py

@@ -76,7 +76,9 @@ def mpi(self) -> bool:
     def openmp(self) -> bool:
         ''':returns: if the compiler supports openmp or not
         '''
-        return self._openmp_flag != ""
+        # It is important not to use `_openmp_flag` directly, since a compiler
+        # wrapper overwrites `openmp_flag`.
+        return self.openmp_flag != ""
 
     @property
     def openmp_flag(self) -> str:

source/fab/tools/linker.py

@@ -11,7 +11,7 @@
 
 import os
 from pathlib import Path
-from typing import cast, Dict, List, Optional, Union
+from typing import Dict, List, Optional, Union
 import warnings
 
 from fab.tools.category import Category
@@ -20,47 +20,35 @@
 
 
 class Linker(CompilerSuiteTool):
-    '''This is the base class for any Linker. It takes either another linker
-    instance, or a compiler instance as parameter in the constructor. Exactly
-    one of these must be provided.
-
-    :param compiler: an optional compiler instance
+    '''This is the base class for any Linker. It takes an existing compiler
+    instance as parameter, and optional another linker. The latter is used
+    to get linker settings - for example, linker-mpif90-gfortran will use
+    mpif90-gfortran as compiler (i.e. to test if it is available and get
+    compilation flags), and linker-gfortran as linker. This way a user
+    only has to specify linker flags in the most basic class (gfortran),
+    all other linker wrapper will inherit the settings.
+
+    :param compiler: a compiler instance
     :param linker: an optional linker instance
     :param name: name of the linker
 
     :raises RuntimeError: if both compiler and linker are specified.
     :raises RuntimeError: if neither compiler nor linker is specified.
     '''
 
-    def __init__(self, compiler: Optional[Compiler] = None,
+    def __init__(self, compiler: Compiler,
                  linker: Optional[Linker] = None,
-                 exec_name: Optional[str] = None,
                  name: Optional[str] = None):
 
-        if linker and compiler:
-            raise RuntimeError("Both compiler and linker is specified in "
-                               "linker constructor.")
-        if not linker and not compiler:
-            raise RuntimeError("Neither compiler nor linker is specified in "
-                               "linker constructor.")
         self._compiler = compiler
         self._linker = linker
 
-        search_linker = self
-        while search_linker._linker:
-            search_linker = search_linker._linker
-        final_compiler = search_linker._compiler
         if not name:
-            assert final_compiler   # make mypy happy
-            name = f"linker-{final_compiler.name}"
-
-        if not exec_name:
-            # This will search for the name in linker or compiler
-            exec_name = self.get_exec_name()
+            name = f"linker-{compiler.name}"
 
         super().__init__(
             name=name,
-            exec_name=exec_name,
+            exec_name=compiler.exec_name,
             suite=self.suite,
             category=Category.LINKER)
 
@@ -76,51 +64,31 @@ def check_available(self) -> bool:
         ''':returns: whether this linker is available by asking the wrapped
             linker or compiler.
         '''
-        if self._compiler:
-            return self._compiler.check_available()
-        assert self._linker   # make mypy happy
-        return self._linker.check_available()
-
-    def get_exec_name(self) -> str:
-        ''':returns: the name of the executable by asking the wrapped
-        linker or compiler.'''
-        if self._compiler:
-            return self._compiler.exec_name
-        assert self._linker   # make mypy happy
-        return self._linker.exec_name
+        return self._compiler.check_available()
 
     @property
     def suite(self) -> str:
         ''':returns: the suite this linker belongs to by getting it from
-            the wrapper compiler or linker.'''
-        return cast(CompilerSuiteTool, (self._compiler or self._linker)).suite
+            the wrapped compiler.'''
+        return self._compiler.suite
 
     @property
     def mpi(self) -> bool:
         ''':returns" whether this linker supports MPI or not by checking
-            with the wrapper compiler or linker.'''
-        if self._compiler:
-            return self._compiler.mpi
-        assert self._linker   # make mypy happy
-        return self._linker.mpi
+            with the wrapped compiler.'''
+        return self._compiler.mpi
 
     @property
     def openmp(self) -> bool:
-        ''':returns" whether this linker supports OpenMP or not by checking
-            with the wrapper compiler or linker.'''
-        if self._compiler:
-            return self._compiler.openmp
-        assert self._linker   # make mypy happy
-        return self._linker.openmp
+        ''':returns: whether this linker supports OpenMP or not by checking
+            with the wrapped compiler.'''
+        return self._compiler.openmp
 
     @property
     def output_flag(self) -> str:
         ''':returns: the flag that is used to specify the output name.
         '''
-        if self._compiler:
-            return self._compiler.output_flag
-        assert self._linker   # make mypy happy
-        return self._linker.output_flag
+        return self._compiler.output_flag
 
     def get_lib_flags(self, lib: str) -> List[str]:
         '''Gets the standard flags for a standard library
@@ -238,18 +206,10 @@ def link(self, input_files: List[Path], output_file: Path,
 
         params: List[Union[str, Path]] = []
 
-        # Find the compiler by following the (potentially
-        # layered) linker wrapper.
-        linker = self
-        while linker._linker:
-            linker = linker._linker
-        # Now we must have a compiler
-        compiler = linker._compiler
-        assert compiler   # make mypy happy
-        params.extend(compiler.flags)
+        params.extend(self._compiler.flags)
 
         if openmp:
-            params.append(compiler.openmp_flag)
+            params.append(self._compiler.openmp_flag)
 
         # TODO: why are the .o files sorted? That shouldn't matter
         params.extend(sorted(map(str, input_files)))

source/fab/tools/tool_repository.py

@@ -117,19 +117,19 @@ def add_tool(self, tool: Tool):
             compiler = cast(Compiler, tool)
             if isinstance(compiler, CompilerWrapper):
                 # If we have a compiler wrapper, create a new linker using
-                # the linker based on the wrappped compiler. For example, when
+                # the linker based on the wrapped compiler. For example, when
                 # creating linker-mpif90-gfortran, we want this to be based on
-                # linker-gfortran (and not on the compiler mpif90-gfortran),
-                # since the linker-gfortran might have library definitions
-                # that should be reused. So we first get the existing linker
-                # (since the compiler exists, a linker for this compiler was
-                # already created and must exist).
+                # linker-gfortran. The compiler mpif90-gfortran will be the
+                # wrapper compiler. Reason is that e.g. linker-gfortran might
+                # have library definitions that should be reused. So we first
+                # get the existing linker (since the compiler exists, a linker
+                # for this compiler was already created and must exist).
                 other_linker = self.get_tool(
                     category=Category.LINKER,
                     name=f"linker-{compiler.compiler.name}")
                 other_linker = cast(Linker, other_linker)
-                linker = Linker(linker=other_linker,
-                                exec_name=compiler.exec_name,
+                linker = Linker(compiler,
+                                linker=other_linker,
                                 name=f"linker-{compiler.name}")
                 self[linker.category].append(linker)
             else:

tests/unit_tests/tools/test_compiler_wrapper.py

@@ -257,6 +257,18 @@ def test_compiler_wrapper_flags_independent():
     assert mpicc.flags == ["-a", "-b"]
     assert mpicc.openmp_flag == gcc.openmp_flag
 
+    # Test  a compiler wrapper correctly queries the wrapper compiler for
+    # openmp flag: Set the wrapper to have no _openmp_flag (which is
+    # actually the default, since the wrapper never sets its own flag), but
+    # gcc does have a flag, so mpicc should report that is supports openmp.
+    # mpicc.openmp calls openmp of its base class (Compiler), which queries
+    # if an openmp flag is defined. This query must go to the openmp property,
+    # since the wrapper overwrites this property to return the wrapped
+    # compiler's flag (and not the wrapper's flag, which would not be defined)
+    with mock.patch.object(mpicc, "_openmp_flag", ""):
+        assert mpicc._openmp_flag == ""
+        assert mpicc.openmp
+
     # Adding flags to the wrapper should not affect the wrapped compiler:
     mpicc.add_flags(["-d", "-e"])
     assert gcc.flags == ["-a", "-b"]

tests/unit_tests/tools/test_linker.py

@@ -41,28 +41,15 @@ def test_linker(mock_c_compiler, mock_fortran_compiler):
     assert linker.flags == []
 
 
-def test_linker_constructor_error(mock_c_compiler):
-    '''Test the linker constructor with invalid parameters.'''
-
-    with pytest.raises(RuntimeError) as err:
-        Linker()
-    assert ("Neither compiler nor linker is specified in linker constructor."
-            in str(err.value))
-    with pytest.raises(RuntimeError) as err:
-        Linker(compiler=mock_c_compiler, linker=mock_c_compiler)
-    assert ("Both compiler and linker is specified in linker constructor."
-            in str(err.value))
-
-
 @pytest.mark.parametrize("mpi", [True, False])
 def test_linker_mpi(mock_c_compiler, mpi):
     '''Test that linker wrappers handle MPI as expected.'''
 
     mock_c_compiler._mpi = mpi
-    linker = Linker(compiler=mock_c_compiler)
+    linker = Linker(mock_c_compiler)
     assert linker.mpi == mpi
 
-    wrapped_linker = Linker(linker=linker)
+    wrapped_linker = Linker(mock_c_compiler, linker=linker)
     assert wrapped_linker.mpi == mpi
 
 
@@ -80,7 +67,7 @@ def test_linker_openmp(mock_c_compiler, openmp):
     linker = Linker(compiler=mock_c_compiler)
     assert linker.openmp == openmp
 
-    wrapped_linker = Linker(linker=linker)
+    wrapped_linker = Linker(mock_c_compiler, linker=linker)
     assert wrapped_linker.openmp == openmp
 
 
@@ -103,7 +90,7 @@ def test_linker_check_available(mock_c_compiler):
 
     # Then test the usage of a linker wrapper. The linker will call the
     # corresponding function in the wrapper linker:
-    wrapped_linker = Linker(linker=linker)
+    wrapped_linker = Linker(mock_c_compiler, linker=linker)
     with mock.patch('fab.tools.compiler.Compiler.get_version',
                     return_value=(1, 2, 3)):
         assert wrapped_linker.check_available()
@@ -342,7 +329,7 @@ def test_linker_nesting(mock_c_compiler):
     linker1.add_lib_flags("lib_a", ["a_from_1"])
     linker1.add_lib_flags("lib_c", ["c_from_1"])
     linker1.add_post_lib_flags(["post_lib1"])
-    linker2 = Linker(linker=linker1)
+    linker2 = Linker(mock_c_compiler, linker=linker1)
     linker2.add_pre_lib_flags(["pre_lib2"])
     linker2.add_lib_flags("lib_b", ["b_from_2"])
     linker2.add_lib_flags("lib_c", ["c_from_2"])

tests/unit_tests/tools/test_tool_repository.py

@@ -11,7 +11,7 @@
 import pytest
 
 from fab.tools import (Ar, Category, FortranCompiler, Gcc, Gfortran, Ifort,
-                       Linker, ToolRepository)
+                       ToolRepository)
 
 
 def test_tool_repository_get_singleton_new():
@@ -62,10 +62,6 @@ def test_tool_repository_get_default():
                               openmp=False)
     assert isinstance(gfortran, Gfortran)
 
-    gcc_linker = tr.get_default(Category.LINKER, mpi=False, openmp=False)
-    assert isinstance(gcc_linker, Linker)
-    assert gcc_linker.name == "linker-gcc"
-
     gcc = tr.get_default(Category.C_COMPILER, mpi=False, openmp=False)
     assert isinstance(gcc, Gcc)