[test] Gate std::filesystem and std::span JIT tests on libstdc++ support

test/support.py

@@ -115,4 +115,30 @@ def setup_make(targetname):
                                             #endif\n""")
     == 1
 )
+
+
+def _jit_resolves_std_filesystem():
+    # The JIT resolves std::filesystem against the loaded libstdc++.so, not
+    # the compile headers -- a manylinux image (gcc-toolset headers over a
+    # GCC-8 base runtime) compiles the include yet dies resolving the
+    # symbols. That failure is a fatal JIT error, so ask in a child process.
+    probe = (
+        "import cppjit\n"
+        'cppjit.cppdef("""#include <filesystem>\n'
+        "unsigned long fs_probe() { return std::filesystem::temp_directory_path().string().size(); }\n"
+        '""")\n'
+        "assert cppjit.gbl.fs_probe() > 0\n"
+    )
+    try:
+        return (
+            subprocess.run(
+                [sys.executable, "-c", probe], capture_output=True, timeout=300
+            ).returncode
+            == 0
+        )
+    except subprocess.TimeoutExpired:
+        return False
+
+
+CAN_JIT_STD_FILESYSTEM = _jit_resolves_std_filesystem()
 IS_VALGRIND = True if os.getenv("IS_VALGRIND") else False

test/test_fragile.py

@@ -943,7 +943,7 @@ def test05_span_compatibility(self):
         import cppjit
 
         cppjit.cppdef("""\
-        #if __cplusplus >= 202002
+        #if __cplusplus >= 202002 && __has_include(<span>)
         #include <span>
         std::span<int> my_test_span1;
         #endif

test/test_regression.py

@@ -3,6 +3,7 @@
 
 from pytest import mark, raises, skip
 from support import (
+    CAN_JIT_STD_FILESYSTEM,
     IS_CLANG_REPL,
     IS_CLING,
     IS_MAC,
@@ -1052,6 +1053,10 @@ def test34_print_empty_collection(self):
         v = cppjit.gbl.std.vector[int]()
         str(v)
 
+    @mark.skipif(
+        not CAN_JIT_STD_FILESYSTEM,
+        reason="std::filesystem is unresolvable in the JIT on libstdc++ < 9",
+    )
     @mark.xfail(condition=IS_CLING, run=False, reason="Crashes on Cling")
     def test35_filesytem(self):
         """Static path object used to crash on destruction"""

test/test_stltypes.py

@@ -2328,13 +2328,25 @@ def test04_from_cpp(self):
         assert cppjit.gbl.GetMyErrorCount() == 0
 
 
-def has_cpp_20():
+def has_std_span():
     import cppjit
 
-    return cppjit.evaluate("__cplusplus") >= 202002
+    # The -std flag is not enough: the JIT uses the system libstdc++ headers,
+    # and <span> only exists there from GCC 10 (absent on the manylinux GCC-8
+    # floor). Gate on the header actually being includable.
+    return (
+        cppjit.evaluate("""#if __cplusplus >= 202002L && __has_include(<span>)
+                                            1
+                                            #else
+                                            0
+                                            #endif""")
+        == 1
+    )
 
 
-@mark.skipif(not has_cpp_20(), reason="std::span requires C++20")
+@mark.skipif(
+    not has_std_span(), reason="std::span needs C++20 and <span> (libstdc++ >= 10)"
+)
 class TestSTLSPAN:
     import cppjit