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Guard cxxabi.h include with __has_include for clang-cl #6145

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Merged
rwgk merged 2 commits into from
Aug 16, 2026
+11 −1
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Guard cxxabi.h include with __has_include for clang-cl #6145

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d91d088
fix: guard cxxabi.h include with __has_include for clang-cl
Aug 16, 2026
0fee21e
docs: explain the __has_include fallback for GCC < 5
Aug 16, 2026
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12 changes: 11 additions & 1 deletion include/pybind11/detail/typeid.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,16 @@
#include <cstdlib>

#if defined(__GNUG__)
# if !defined(__has_include)
// All supported Clang versions provide __has_include, but GCC versions before 5 do not.
// Preserve the previous unconditional __GNUG__ behavior for those older, still-supported
// GCC versions (see PR #6145).
# define PYBIND11_HAS_CXXABI_H

@rwgk rwgk Aug 16, 2026

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Suggested change
# define PYBIND11_HAS_CXXABI_H
// All supported Clang versions provide __has_include, but GCC versions before 5 do not.
// Preserve the previous unconditional __GNUG__ behavior for those older, still-supported
// GCC versions (see PR #6145).
# define PYBIND11_HAS_CXXABI_H

This fallback is not self-explanatory and could, in principle, misidentify another GNU-compatible toolchain as providing <cxxabi.h>. I think it is important to document why preserving the old behavior is intentional for pybind11’s currently supported compiler range. It also leaves a useful hint for later: once pybind11 no longer supports GCC versions before 5, the fallback can be removed.

# elif __has_include(<cxxabi.h>)
# define PYBIND11_HAS_CXXABI_H
# endif
#endif
#if defined(PYBIND11_HAS_CXXABI_H)
# include <cxxabi.h>
#endif

Expand All @@ -33,7 +43,7 @@ inline void erase_all(std::string &string, const std::string &search) {
}

PYBIND11_NOINLINE void clean_type_id(std::string &name) {
#if defined(__GNUG__)
#if defined(PYBIND11_HAS_CXXABI_H)
int status = 0;
std::unique_ptr<char, void (*)(void *)> res{
abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status), std::free};
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