When compiling folly on Fedora 35 with gcc from the included 11.2.1-7 package, I found that the badge_test code fails to compile, whereas it builds fine with gcc 10.x and with the fedora 35 clang (13.0.0-3.fc35)). Bisecting from https://gcc.gnu.org/git/gcc.git with pre-processed source indicates problem introduced in commit: [a2531859bf5bf6cf1f29c0dca85fd26e80904a5d] c++: Alias template in pack expansion [PR99445] Bisected with commands, (bisection script below) git bisect start basepoints/gcc-12 basepoints/gcc-11 git bisect run ~/local/bisect/gxx_bisect.sh Example of the problem from a folly build along with the command line I got preprocessed source from is in https://github.com/facebook/folly/commit/af966d2ce25c14c96373bf39c8ae2b406219ffb4 Error looks like: '/home/alex/local/bisect/test/0cc79337ad265aabccab63882a810f9dc509a9d0/build' In file included from /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:19: /home/alex/local/folly/folly/lang/Badge.h: In instantiation of ‘class folly::any_badge<{anonymous}::FriendClass, {anonymous}::OtherFriendClass>’: /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:38:40: required from here /home/alex/local/folly/folly/lang/Badge.h:99:18: error: expansion pattern ‘folly::StrictDisjunction<std::is_same<OtherHolders, Holders>...>’ contains no parameter packs 99 | /* implicit */ any_badge(any_badge<OtherHolders...>) noexcept {} | ^~~~~~~~~ /home/alex/local/folly/folly/lang/Badge.h: In instantiation of ‘class folly::any_badge<{anonymous}::FriendClass, {anonymous}::OtherFriendClass, {anonymous}::DummyClass>’: /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:39:53: required from here /home/alex/local/folly/folly/lang/Badge.h:99:18: error: expansion pattern ‘folly::StrictDisjunction<std::is_same<OtherHolders, Holders>...>’ contains no parameter packs /home/alex/local/folly/folly/lang/test/BadgeTest.cpp: In static member function ‘static void {anonymous}::ProtectedClass::subset({anonymous}::SubsetBadges)’: /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:39:54: error: cannot convert ‘any_badge<{anonymous}::FriendClass, {anonymous}::OtherFriendClass>’ to ‘any_badge<{anonymous}::FriendClass, {anonymous}::OtherFriendClass, {anonymous}::DummyClass>’ 39 | static void subset(SubsetBadges badges) { superset(badges); } | ^~~~~~ | | | any_badge<{anonymous}::FriendClass, {anonymous}::OtherFriendClass> /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:40:24: note: initializing argument 1 of ‘static void {anonymous}::ProtectedClass::superset({anonymous}::SupersetBadges)’ 40 | static void superset(SupersetBadges) {} | ^~~~~~~~~~~~~~ In file included from /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:19: /home/alex/local/folly/folly/lang/Badge.h: In instantiation of ‘class folly::any_badge<{anonymous}::FriendClass>’: /home/alex/local/folly/folly/lang/test/BadgeTest.cpp:47:35: required from here /home/alex/local/folly/folly/lang/Badge.h:99:18: error: expansion pattern ‘folly::StrictDisjunction<std::is_same<OtherHolders, Holders>...>’ contains no parameter packs 99 | /* implicit */ any_badge(any_badge<OtherHolders...>) noexcept {} | ^~~~~~~~~ Exited with 0 Bisection script was: #!/bin/sh # adapted from http://moxielogic.org/blog/bisecting-gcc.html # Test with: # cd local/gcc #(or whereever gcc git repo is) # ./bisect/gxx_bisect.sh # Run with: # git bisect run ~/local/bisect/gxx_bisect.sh # git clone of the gcc tree GCCSRC="$HOME/local/gcc" # pre-processed test case TESTSRC="$HOME/local/bisect/bisect_source.i" COMMIT=`git rev-parse HEAD` # Where to put gcc build and install dirs testdir="$HOME/local/bisect/test/$COMMIT" mkdir -p "$testdir/build" mkdir -p "$testdir/install" # configure for C & C++ (cd "$testdir/build" && $GCCSRC/configure --prefix="$testdir/install" --enable-languages=c,c++ --with-system-zlib --disable-multilib --disable-libsanitizer --disable-bootstrap && make -j 32 && make -j 32 install) cxxbin="$testdir/install/bin/g++" if test -x "$cxxbin"; then # build test case if "$cxxbin" -std=gnu++17 -c "$TESTSRC"; then # everything's fine exit 0 fi # gcc can return exit codes outside of git's acceptable range, so... echo "Exited with $?" 1>&2 exit 1 else # No binary, skip broken builds with special 125 exit code exit 125 fi
