handle use of an unconfigured compiler (#41213)

2 files changed, 19 insertions, 1 deletions

diff --git a/lib/spack/spack/build_environment.py b/lib/spack/spack/build_environment.py
index 36574259d0..20d8e75f9b 100644
--- a/lib/spack/spack/build_environment.py
+++ b/lib/spack/spack/build_environment.py
@@ -324,19 +324,29 @@ def set_compiler_environment_variables(pkg, env):
     # ttyout, ttyerr, etc.
     link_dir = spack.paths.build_env_path
 
-    # Set SPACK compiler variables so that our wrapper knows what to call
+    # Set SPACK compiler variables so that our wrapper knows what to
+    # call.  If there is no compiler configured then use a default
+    # wrapper which will emit an error if it is used.
     if compiler.cc:
         env.set("SPACK_CC", compiler.cc)
         env.set("CC", os.path.join(link_dir, compiler.link_paths["cc"]))
+    else:
+        env.set("CC", os.path.join(link_dir, "cc"))
     if compiler.cxx:
         env.set("SPACK_CXX", compiler.cxx)
         env.set("CXX", os.path.join(link_dir, compiler.link_paths["cxx"]))
+    else:
+        env.set("CC", os.path.join(link_dir, "c++"))
     if compiler.f77:
         env.set("SPACK_F77", compiler.f77)
         env.set("F77", os.path.join(link_dir, compiler.link_paths["f77"]))
+    else:
+        env.set("F77", os.path.join(link_dir, "f77"))
     if compiler.fc:
         env.set("SPACK_FC", compiler.fc)
         env.set("FC", os.path.join(link_dir, compiler.link_paths["fc"]))
+    else:
+        env.set("FC", os.path.join(link_dir, "fc"))
 
     # Set SPACK compiler rpath flags so that our wrapper knows what to use
     env.set("SPACK_CC_RPATH_ARG", compiler.cc_rpath_arg)
diff --git a/lib/spack/spack/compilers/__init__.py b/lib/spack/spack/compilers/__init__.py
index 6366fc321b..be9edeecb4 100644
--- a/lib/spack/spack/compilers/__init__.py
+++ b/lib/spack/spack/compilers/__init__.py
@@ -154,6 +154,14 @@ def add_compilers_to_config(compilers, scope=None, init_config=True):
     """
     compiler_config = get_compiler_config(scope, init_config)
     for compiler in compilers:
+        if not compiler.cc:
+            tty.debug(f"{compiler.spec} does not have a C compiler")
+        if not compiler.cxx:
+            tty.debug(f"{compiler.spec} does not have a C++ compiler")
+        if not compiler.f77:
+            tty.debug(f"{compiler.spec} does not have a Fortran77 compiler")
+        if not compiler.fc:
+            tty.debug(f"{compiler.spec} does not have a Fortran compiler")
         compiler_config.append(_to_dict(compiler))
     spack.config.set("compilers", compiler_config, scope=scope)