amykhuang wrote:
> We have internal reports of incorrect mangling substitutions after updating
> to
> [537b654](https://github.com/llvm/llvm-project/commit/537b6541e8067d7ef7aa38791989fca6303b7fdf)
> from
> [799e905](https://github.com/llvm/llvm-project/commit/799e9053641a6478d3144866a97737b37b87c260),
> and this change seems like the likely culprit because it's touching the
> Itanium mangling code. We'll see if that can be confirmed.
Confirmed it is due to this change; the bug report is that some instances of
`absl::container_internal::AbslHashValue` have an incorrect mangled name.
The internal repro builds a test with a dependency on a file like
```
$ cat hash_mangling.cc
#include "[...]/hash_mangling.h"
#include <string>
#include "third_party/absl/container/flat_hash_set.h"
void f(absl::flat_hash_set<absl::flat_hash_set<std::string>>& s,
const absl::flat_hash_set<std::string>& k) {
s.insert(k);
}
$ llvm-readelf-19 -s -W hash_mangling.pic.o | grep XsrNT_S6_11is_hashable
26: 0000000000000000 336 FUNC WEAK DEFAULT 39
_ZN4absl18container_internal13AbslHashValueINS_13hash_internal15MixingHashStateEEENSt3__u9enable_ifIXsrNT_S6_11is_hashableINS4_12basic_stringIcNS4_11char_traitsIcEENS4_9allocatorIcEEEEEE5valueES6_E4typeES6_RKNS0_12raw_hash_setINS0_17FlatHashSetPolicyISD_EENS0_10StringHashENS0_8StringEqENSB_ISD_EEEE
```
>From the internal bug report,
> The error here is the substitution S6_ in ...XsrNT_S6_11is_hashable.... The
> grammar for <unresolved-name> in
> https://itanium-cxx-abi.github.io/cxx-abi/abi.html#expressions does not
> permit a substitution here. S6_ would refer to T_, the immediately preceding
> use of the template parameter. It is as if the H:: in H::template
> is_hashable<value_type>::value at
> `absl/container/internal/raw_hash_set.h;l=3020` is being accidentally encoded
> twice.
I'm still trying to come up with a reduced repro though.
https://github.com/llvm/llvm-project/pull/133610
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