cxx: new test API (#45462)

* cxx: new test API
* gcc: provide cxx
* default providers:  cxx provided by gcc
* cxx: cleanup stand-alone test
  - test_c -> test_cxx
  - simplify compilation and execution
  - corrected output checks

---------

Co-authored-by: Tamara Dahlgren <dahlgren1@llnl.gov>

etc/spack/defaults/packages.yaml

@@ -20,6 +20,7 @@ packages:
       awk: [gawk]
       armci: [armcimpi]
       blas: [openblas, amdblis]
+      cxx: [gcc]
       D: [ldc]
       daal: [intel-oneapi-daal]
       elf: [elfutils]

var/spack/repos/builtin/packages/cxx/package.py

@@ -14,28 +14,27 @@ class Cxx(Package):
     homepage = "https://isocpp.org/std/the-standard"
     virtual = True
 
-    def test(self):
+    def test_cxx(self):
+        """Compile and run 'Hello World'"""
+        cxx = which(os.environ["CXX"])
+        expected = ["Hello world", "YES!"]
+
         test_source = self.test_suite.current_test_data_dir
-
         for test in os.listdir(test_source):
-            filepath = os.path.join(test_source, test)
-            exe_name = "%s.exe" % test
+            exe_name = f"{test}.exe"
+            filepath = test_source.join(test)
+            with test_part(self, f"test_cxx_{test}", f"build and run {exe_name}"):
+                # standard options
+                # Hack to get compiler attributes
+                # TODO: remove this when compilers are dependencies
+                c_name = clang if self.spec.satisfies("llvm+clang") else self.name
+                c_spec = spack.spec.CompilerSpec(c_name, self.spec.version)
+                c_cls = spack.compilers.class_for_compiler_name(c_name)
+                compiler = c_cls(c_spec, None, None, ["fakecc", "fakecxx"])
+                cxx_opts = [compiler.cxx11_flag] if "c++11" in test else []
+                cxx_opts += ["-o", exe_name, filepath]
 
-            cxx_exe = os.environ["CXX"]
-
-            # standard options
-            # Hack to get compiler attributes
-            # TODO: remove this when compilers are dependencies
-            c_name = clang if self.spec.satisfies("llvm+clang") else self.name
-            c_spec = spack.spec.CompilerSpec(c_name, self.spec.version)
-            c_cls = spack.compilers.class_for_compiler_name(c_name)
-            compiler = c_cls(c_spec, None, None, ["fakecc", "fakecxx"])
-
-            cxx_opts = [compiler.cxx11_flag] if "c++11" in test else []
-
-            cxx_opts += ["-o", exe_name, filepath]
-            compiled = self.run_test(cxx_exe, options=cxx_opts, installed=True)
-
-            if compiled:
-                expected = ["Hello world", "YES!"]
-                self.run_test(exe_name, expected=expected)
+                cxx(*cxx_opts)
+                exe = which(exe_name)
+                out = exe(output=str.split, error=str.split)
+                check_outputs(expected, out)

var/spack/repos/builtin/packages/gcc/package.py

@@ -34,6 +34,8 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage, CompilerPackage):
 
     license("GPL-2.0-or-later AND LGPL-2.1-or-later")
 
+    provides("cxx")
+
     version("master", branch="master")
 
     version("14.2.0", sha256="a7b39bc69cbf9e25826c5a60ab26477001f7c08d85cec04bc0e29cabed6f3cc9")