From d348d37c5a18a1e3a9fd5407faa633fb4a79e3b8 Mon Sep 17 00:00:00 2001
From: Bernhard Kaindl <bernhardkaindl7@gmail.com>
Date: Fri, 21 Aug 2026 02:43:37 +0200
Subject: [PATCH] autotools: skip compiler prefixes in autoreconf search path

---
 .../builtin/build_systems/autotools.py         |  7 ++++++-
 tests/build_systems.py                         | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/repos/spack_repo/builtin/build_systems/autotools.py b/repos/spack_repo/builtin/build_systems/autotools.py
index bcdff9159ea..8866c5e5d67 100644
--- a/repos/spack_repo/builtin/build_systems/autotools.py
+++ b/repos/spack_repo/builtin/build_systems/autotools.py
@@ -6,6 +6,7 @@
 import subprocess
 from typing import Callable, List, Optional, Set, Tuple, Union
 
+from spack import deptypes
 from spack.package import (
     BuilderWithDefaults,
     Executable,
@@ -856,7 +857,11 @@ def _autoreconf_search_path_args(spec: Spec) -> List[str]:
         except OSError:
             pass
 
-    for dep in spec.dependencies(deptype="build"):
+    for edge in spec.edges_to_dependencies(depflag=deptypes.BUILD):
+        # compiler prefixes might have foreign aclocal files which we do not want to include
+        if any(language in edge.virtuals for language in ("c", "cxx", "fortran")):
+            continue
+        dep = edge.spec
         path = dep.prefix.share.aclocal
         # Skip non-existing aclocal paths
         try:
diff --git a/tests/build_systems.py b/tests/build_systems.py
index 3d094af92e5..aa374aba8e6 100644
--- a/tests/build_systems.py
+++ b/tests/build_systems.py
@@ -448,6 +448,24 @@ def test_autoreconf_search_path_args_external_order(
     ]
 
 
+def test_autoreconf_search_path_args_skip_compiler(
+    default_mock_concretization, tmp_path: pathlib.Path
+):
+    """Compiler prefixes are not aclocal macro providers."""
+    spec = default_mock_concretization("dttop")
+    compiler, macro_provider = spec.dependencies(deptype="build")
+    compiler_aclocal = tmp_path / "compiler" / "share" / "aclocal"
+    provider_aclocal = tmp_path / "provider" / "share" / "aclocal"
+    compiler_aclocal.mkdir(parents=True)
+    provider_aclocal.mkdir(parents=True)
+    compiler.external_path = str(tmp_path / "compiler")
+    macro_provider.set_prefix(str(tmp_path / "provider"))
+    compiler_edge = next(edge for edge in spec.edges_to_dependencies() if edge.spec is compiler)
+    compiler_edge.virtuals = ("c", "cxx")
+
+    assert autotools._autoreconf_search_path_args(spec) == ["-I", str(provider_aclocal)]
+
+
 def test_autoreconf_search_path_skip_nonexisting(
     default_mock_concretization, tmp_path: pathlib.Path
 ):