From: Kyrylo Tkachov <[email protected]>
xtreme-header-8.C is the only xtreme-header test that builds a named
module, so [basic.link]/17 applies to it and exposing a TU-local entity
is ill-formed. libstdc++ selects the PSTL backend from
__has_include(<tbb/tbb.h>), so on a machine with oneTBB installed
<execution> pulls third-party headers into the module purview. oneTBB
names namespace-scope statics and constants from inline member functions
of externally linked classes, which GCC correctly rejects, and the test
fails for reasons that have nothing to do with libstdc++ or the modules
implementation.
The failure dates back to r15-6379-g0c2ae3843261 ("c++/modules: Ignore
TU-local entities where necessary"), which added the test. The exposure
diagnostic already existed then, so the test has failed on a host with
oneTBB installed since the day it landed. That commit message does note
the hazard, "unfortunately the system headers on some
targets declare TU-local entities", but the third-party headers reached
through <execution> were not considered.
_GLIBCXX_USE_TBB_PAR_BACKEND is a documented user-overridable knob, and
libstdc++ already suppresses the TBB backend the same way for module std
(r15-5366-g7db55c0ba1ba). Define it to 0 so the test exercises what it
is meant to exercise regardless of what happens to be installed on the
test machine.
Tested on aarch64-none-linux-gnu.
Ok for trunk?
Thanks,
Kyrill
gcc/testsuite/ChangeLog:
* g++.dg/modules/xtreme-header-8.C: Select the serial PSTL
backend.
Signed-off-by: Kyrylo Tkachov <[email protected]>
---
gcc/testsuite/g++.dg/modules/xtreme-header-8.C | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
b/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
index dc8ae240ffe..013fbb83c42 100644
--- a/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
+++ b/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
@@ -1,5 +1,8 @@
// PR c++/115126
-// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local" }
+// Force the serial PSTL backend. If oneTBB is installed, <execution>
+// pulls third-party headers that expose TU-local entities into the
+// module purview, which is ill-formed in a module interface unit.
+// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local
-D_GLIBCXX_USE_TBB_PAR_BACKEND=0" }
// { dg-module-cmi xstd }
// { dg-skip-if "required hosted libstdc++ for any in xtreme-header.h" { !
hostedlib } }
--
2.50.1 (Apple Git-155)
