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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.
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MSVC compatibility¶. When Clang compiles C++ code for Windows, it attempts to be compatible with MSVC. There are multiple dimensions to compatibility. First, Clang attempts to be ABI-compatible, meaning that Clang-compiled code should be able to link against MSVC-compiled code successfully.
The Clang Compiler is an open-source compiler for the C family of programming languages, aiming to be the best in class implementation of these languages. Clang builds on the LLVM optimizer and code generator, allowing it to provide high-quality optimization and code generation support for many targets.
Codes were as simple as the one shown below. The first name in the comment is the GCC mangled name (g++ 8.3) and the second name is the Clang mangled name (clang++ 9.0). So, at least given this small set of samples, there do not seem to be differences.
Clang also provides an alternative driver, clang-cl, that is designed to be compatible with the Visual C++ compiler, cl.exe. In addition to language specific features, Clang has a variety of features that depend on what CPU architecture or operating system is being compiled for.
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.
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