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[libcxx] Use local names for the operator new impl symbols #122983

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[libcxx] Use local names for the operator new impl symbols #122983

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6c66527
[libcxx] Use local names for the operator new impl symbols
petrhosek Jan 14, 2025
00ec430
Make the impl symbols non-static
petrhosek Jan 14, 2025
4958c19
Make the impl symbols static
petrhosek Jan 15, 2025
9c0ffae
Use local symbols for the implementation
petrhosek Jan 15, 2025
f76dd14
Use C++ attributes
petrhosek Jan 15, 2025
7b6b05c
Update the Mach-O implementation
petrhosek Jan 21, 2025
82c9331
Use correct attributes for functions
petrhosek Jan 21, 2025
0255ef6
Provide forward declaration to make GCC happy
petrhosek Jan 21, 2025
80c35b3
Use suffixed names for internal aliases
petrhosek Jan 22, 2025
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8 changes: 8 additions & 0 deletions libcxx/include/__config
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Original file line number Diff line number Diff line change
Expand Up @@ -804,6 +804,14 @@ typedef __char32_t char32_t;
# define _LIBCPP_WEAK __attribute__((__weak__))
# endif

# ifndef _LIBCPP_WEAK_IMPORT
# define _LIBCPP_WEAK_IMPORT __attribute__((weak_import))
# endif

# ifndef _LIBCPP_ALIAS
# define _LIBCPP_ALIAS(x) __attribute__((alias(x)))
# endif

// Thread API
// clang-format off
# if _LIBCPP_HAS_THREADS && \
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33 changes: 13 additions & 20 deletions libcxx/src/include/overridable_function.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,6 @@
#include <__config>
#include <cstdint>

#if __has_feature(ptrauth_calls)
# include <ptrauth.h>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
Expand All @@ -42,12 +38,11 @@
// -------------------
//
// Let's say we want to check whether a weak function `f` has been overridden by the user.
// The general mechanism works by defining a symbol `f_impl__` and a weak alias `f` via the
// _LIBCPP_OVERRIDABLE_FUNCTION macro.
//
// Then, when comes the time to check whether the function has been overridden, we take
// the address of the function `f` and we check whether it is different from `f_impl__`.
// If so it means the function was overriden by the user.
// The general mechanism works by defining an internal symbol and a weak alias `f` via the
// _LIBCPP_OVERRIDABLE_FUNCTION macro. Then, when comes the time to check whether the
// function has been overridden, we take the address of the internal symbol and the weak
// alias `f` and check whether they're different. If so it means the function was overriden
// by the user.
//
// Important note
// --------------
Expand All @@ -67,17 +62,15 @@ _LIBCPP_END_NAMESPACE_STD

# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1
# define _LIBCPP_OVERRIDABLE_FUNCTION(symbol, type, name, arglist) \
static __attribute__((used)) type symbol##_impl__ arglist __asm__("_" _LIBCPP_TOSTRING(symbol)); \
__asm__(".globl _" _LIBCPP_TOSTRING(symbol)); \
__asm__(".weak_definition _" _LIBCPP_TOSTRING(symbol)); \
extern __typeof(symbol##_impl__) name __attribute__((weak_import)); \
_LIBCPP_WEAK type name arglist; \
_LIBCPP_WEAK_IMPORT extern type symbol##_impl arglist __asm__("_" _LIBCPP_TOSTRING(symbol)); \
_LIBCPP_BEGIN_NAMESPACE_STD \
template <> \
inline bool __is_function_overridden<static_cast<type(*) arglist>(name)>() { \
return static_cast<type(*) arglist>(name) != symbol##_impl__; \
return static_cast<type(*) arglist>(name) != symbol##_impl; \
} \
_LIBCPP_END_NAMESPACE_STD \
static type symbol##_impl__ arglist
type name arglist

#elif defined(_LIBCPP_OBJECT_FORMAT_ELF)

Expand All @@ -90,15 +83,15 @@ _LIBCPP_END_NAMESPACE_STD

# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1
# define _LIBCPP_OVERRIDABLE_FUNCTION(symbol, type, name, arglist) \
static type symbol##_impl__ arglist __asm__(_LIBCPP_TOSTRING(symbol##_impl__)); \
[[gnu::weak, gnu::alias(_LIBCPP_TOSTRING(symbol##_impl__))]] type name arglist; \
_LIBCPP_WEAK type name arglist; \
_LIBCPP_ALIAS(_LIBCPP_TOSTRING(symbol)) static type symbol##_impl arglist __asm__(".L." _LIBCPP_TOSTRING(symbol)); \
_LIBCPP_BEGIN_NAMESPACE_STD \
template <> \
inline bool __is_function_overridden<static_cast<type(*) arglist>(name)>() { \
return static_cast<type(*) arglist>(name) != symbol##_impl__; \
return static_cast<type(*) arglist>(name) != symbol##_impl; \
} \
_LIBCPP_END_NAMESPACE_STD \
static type symbol##_impl__ arglist
type name arglist

#else

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