Is there a way to use custom mangling in g++/clang++?

Question

When using c++ template, and especially tuples, I often get very long mangled names like

_ZN11__sanitizer13InternalAllocEmPNS_28SizeClassAllocatorLocalCacheINS_20SizeClassAllocator32ILm0ELy140737488355328ELm0ENS_12SizeClassMapILm3ELm4ELm8ELm17ELm64ELm14EEELm20ENS_15TwoLevelByteMapILy32768ELy4096ENS_20NoOpMapUnmapCallbackEEES5_EEEEm

This is obviously fine in nominal case, and ease debugging but, when I use large tuples of custom types (with large namespaces) this ends up with very huge binaries just because of mangled names; Some tools (like valgrind) even have a symbol name maximum length that make analysis almost impossible.

I was wondering if there is a way to ask g++/clang++ to use a custom mangling function (say md5) so that the very long symbol becomes 5c66b1073e1b453900bd7d32cb79fc0e which is way shorter.

Answer 1

The absence of this innovation in any important C++ implementation is accounted for by the fact that a C++ compiler's name-mangling protocol is part of its ABI and can't be the user's choice at the same time.

Notoriously, C++ code compiled with GCC is not interoperable with code compiled with Microsoft compilers because, inter alia, they use different name-mangling protocols. And the fact that they do use different name-mangling protocols, and cannot be directed to use the same one, guarantees that subtler ABI incompatibilities will not survive an attempted linkage.

The constancy of the C++ compiler's name-mangling protocol is also assumed in other toolchain utilities, e.g. binutils nm, objdump.