arch: Fix get_cuda_version when nvcc is missing

devito/arch/archinfo.py

@@ -575,7 +575,7 @@ def get_cuda_version():
         out = run(nvc_version_command, capture_output=True, text=True)
     except (FileNotFoundError, CalledProcessError):
         pass
-    finally:
+    else:
         if out.returncode == 0:
             start = out.stdout.find('release')
             start = out.stdout.find(',', start) + 1

devito/arch/compiler.py

@@ -809,7 +809,8 @@ def __init_finalize__(self, **kwargs):
     @property
     def std(self):
         # Since CUDA 13, code needs compiling with C++17 standard
-        _cxxstd = 'c++17' if get_cuda_version().major >= 13 else 'c++14'
+        cuda_version = get_cuda_version()
+        _cxxstd = 'c++17' if cuda_version and cuda_version.major >= 13 else 'c++14'
         return _cxxstd if self._cpp else self._cstd
 
     def __lookup_cmds__(self):

tests/test_arch.py

@@ -6,6 +6,7 @@
 
 from devito import configuration, switchconfig
 from devito.arch import BLACKWELL, NVIDIAX
+from devito.arch.archinfo import get_cuda_version
 from devito.arch.compiler import (
     CudaCompiler, GNUCompiler, compiler_registry, sniff_compiler_version
 )
@@ -93,3 +94,26 @@ def test_cuda_target(monkeypatch, platform, cc, target):
 
     flags = [i for i in compiler.cflags if i.startswith(('-arch=', '-gencode='))]
     assert flags == [target]
+
+
+def test_get_cuda_version_without_nvcc(monkeypatch):
+    def missing(*args, **kwargs):
+        raise FileNotFoundError('nvcc')
+
+    monkeypatch.setattr('devito.arch.archinfo.run', missing)
+    # `.func` skips the cache
+    assert get_cuda_version.func() is None
+
+
+def test_cuda_std_without_nvcc(monkeypatch):
+    def std(version):
+        with switchconfig(mpi=False), monkeypatch.context() as m:
+            m.setattr('devito.arch.compiler.get_cuda_version', lambda: version)
+            m.setattr('devito.arch.compiler.check_cuda_runtime', lambda: None)
+            return CudaCompiler(platform=NVIDIAX).std
+
+    assert std(Version('13.0')) == 'c++17'
+    assert std(Version('12.8')) == 'c++14'
+    # No `nvcc`: fall back to the pre-CUDA 13 standard
+    assert std(None) == 'c++14'
+