Hi,
This is my first patch to the GCC mailing, so feedback is appreciated. I
may have gone overboard with detail for a mere four-line change. I
noticed trunk builds of libstdc++ broke previously working builds of an
experimental C++ codebase of mine that tests new C++26 features. The
problem can be replicated by compiling the file main.cc containing:
import std;
int main() {}
with:
$ g++ -std=c++26 -fmodules -fsearch-include-path bits/std.cc main.cc
I didn't see any reports of this on the bug tracker, so no PR is
referenced.
-- >8 --
When exporting declarations in a namespace with using declarations, the
name must be fully qualified. Recently introduced std::full_extent{,_t},
std:strided_slice, and std::submdspan_mapping_result broke module std
and module std.compat.
No testcase could be added to the testsuite, as current testing
machinery cannot control the order in which the files are compiled. To
be able to compile a file importing the std module in a single compiler
invocation, the importing file must be named after the file containing
module std, i.e., this works:
$ g++ -std=c++23 -fmodules -fsearch-include-path bits/std.cc importer.cc
while this does not:
$ g++ -std=c++23 -fmodules -fsearch-include-path importer.cc bits/std.cc
so the dg-options test directive is not enough, as it is unspecified in
what order they will be added to the compile line.
The dg-additional-sources directive cannot be used either, as it is
stated in the GCC Internals manual that such added sources will appear in
the compile line _following_ the main test file. Until the proper
functionality is added to the testsuite to handle modules, changes to the
std and std.compat modules should be manually verified to not break the
them.
libstdc++-v3/ChangeLog:
* include/bits/std.cc.in: Fix <mdspan> exports
---
libstdc++-v3/src/c++23/std.cc.in | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index e849307f186..4c11b1bf711 100644
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -1872,10 +1872,10 @@ export namespace std
#if __glibcxx_padded_layouts
using std::layout_left_padded;
using std::layout_right_padded;
- using strided_slice;
- using full_extent_t;
- using full_extent;
- using submdspan_mapping_result;
+ using std::strided_slice;
+ using std::full_extent_t;
+ using std::full_extent;
+ using std::submdspan_mapping_result;
#endif
// FIXME submdspan_extents, mdsubspan
}
--
2.51.1
