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[ItaniumDemangle] Strip __alloc_token_ to transparently demangle allocation functions (#191048)

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Update the Itanium demangler to recognize and strip `__alloc_token_`
prefixes introduced by AllocToken instrumentation [1]. This ensures that
instrumented allocation functions (e.g., `__alloc_token__Znwm`) demangle
back to their original source-level names (e.g., `operator new(unsigned
long)`) with a suffix `(.alloc_token)` indicating their non-standard
origin.

Since AllocToken is intended to be transparent to users who continue to
use `operator new` as before, the demangled name should reflect this
reality instead of confusing users with internal instrumentation names
in stack traces or symbolization output.

Synchronize changes across llvm and libcxxabi copies.

[1] https://clang.llvm.org/docs/AllocToken.html

Original RFC: https://discourse.llvm.org/t/rfc-a-framework-for-allocator-partitioning-hints/87434
This commit is contained in:
Marco Elver 2026-04-22 17:57:30 +02:00 committed by GitHub
parent 42ef1321e6
commit fb6f1bde00
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6 changed files with 70 additions and 0 deletions
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11
libcxxabi/src/demangle/ItaniumDemangle.h
View file

@ -6157,8 +6157,17 @@ AbstractManglingParser<Derived, Alloc>::parseTemplateArgs(bool TagTemplates) {
// extension ::= ___Z <encoding> _block_invoke
// extension ::= ___Z <encoding> _block_invoke<decimal-digit>+
// extension ::= ___Z <encoding> _block_invoke_<decimal-digit>+
// extension ::= __alloc_token__Z <encoding>
// extension ::= __alloc_token_<decimal-digit>+__Z <encoding>
template <typename Derived, typename Alloc>
Node *AbstractManglingParser<Derived, Alloc>::parse(bool ParseParams) {
bool AllocToken = consumeIf("__alloc_token_");
if (AllocToken) {
const char *Saved = First;
if (parseNumber().empty() || !consumeIf('_'))
First = Saved;
}
if (consumeIf("_Z") || consumeIf("__Z")) {
Node *Encoding = getDerived().parseEncoding(ParseParams);
if (Encoding == nullptr)
@ -6168,6 +6177,8 @@ Node *AbstractManglingParser<Derived, Alloc>::parse(bool ParseParams) {
make<DotSuffix>(Encoding, std::string_view(First, Last - First));
First = Last;
}
if (AllocToken)
Encoding = make<DotSuffix>(Encoding, ".alloc_token");
if (numLeft() != 0)
return nullptr;
return Encoding;

11
libcxxabi/test/DemangleTestCases.inc
View file

@ -30219,4 +30219,15 @@
{"_Z3fooIPU9__ptrauthILj1ELb0ELj64EEPiEvT_", "void foo<int* __ptrauth<1u, false, 64u>*>(int* __ptrauth<1u, false, 64u>*)"},
{"_ZN1CpmEi", "C::operator->*(int)"},
// AllocToken instrumentation
{"__alloc_token__Znwm", "operator new(unsigned long) (.alloc_token)"},
{"__alloc_token__Znam", "operator new[](unsigned long) (.alloc_token)"},
{"__alloc_token__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token__ZnamRKSt9nothrow_t", "operator new[](unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token_0__Znwm", "operator new(unsigned long) (.alloc_token)"},
{"__alloc_token_1__Znam", "operator new[](unsigned long) (.alloc_token)"},
{"__alloc_token_123__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token__Znwm.llvm.1234", "operator new(unsigned long) (.llvm.1234) (.alloc_token)"},
{"__alloc_token_123__Z3foov", "foo() (.alloc_token)"},
// clang-format on

11
llvm/include/llvm/Demangle/ItaniumDemangle.h
View file

@ -6157,8 +6157,17 @@ AbstractManglingParser<Derived, Alloc>::parseTemplateArgs(bool TagTemplates) {
// extension ::= ___Z <encoding> _block_invoke
// extension ::= ___Z <encoding> _block_invoke<decimal-digit>+
// extension ::= ___Z <encoding> _block_invoke_<decimal-digit>+
// extension ::= __alloc_token__Z <encoding>
// extension ::= __alloc_token_<decimal-digit>+__Z <encoding>
template <typename Derived, typename Alloc>
Node *AbstractManglingParser<Derived, Alloc>::parse(bool ParseParams) {
bool AllocToken = consumeIf("__alloc_token_");
if (AllocToken) {
const char *Saved = First;
if (parseNumber().empty() || !consumeIf('_'))
First = Saved;
}
if (consumeIf("_Z") || consumeIf("__Z")) {
Node *Encoding = getDerived().parseEncoding(ParseParams);
if (Encoding == nullptr)
@ -6168,6 +6177,8 @@ Node *AbstractManglingParser<Derived, Alloc>::parse(bool ParseParams) {
make<DotSuffix>(Encoding, std::string_view(First, Last - First));
First = Last;
}
if (AllocToken)
Encoding = make<DotSuffix>(Encoding, ".alloc_token");
if (numLeft() != 0)
return nullptr;
return Encoding;

11
llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc
View file

@ -30219,4 +30219,15 @@
{"_Z3fooIPU9__ptrauthILj1ELb0ELj64EEPiEvT_", "void foo<int* __ptrauth<1u, false, 64u>*>(int* __ptrauth<1u, false, 64u>*)"},
{"_ZN1CpmEi", "C::operator->*(int)"},
// AllocToken instrumentation
{"__alloc_token__Znwm", "operator new(unsigned long) (.alloc_token)"},
{"__alloc_token__Znam", "operator new[](unsigned long) (.alloc_token)"},
{"__alloc_token__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token__ZnamRKSt9nothrow_t", "operator new[](unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token_0__Znwm", "operator new(unsigned long) (.alloc_token)"},
{"__alloc_token_1__Znam", "operator new[](unsigned long) (.alloc_token)"},
{"__alloc_token_123__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&) (.alloc_token)"},
{"__alloc_token__Znwm.llvm.1234", "operator new(unsigned long) (.llvm.1234) (.alloc_token)"},
{"__alloc_token_123__Z3foov", "foo() (.alloc_token)"},
// clang-format on

10
llvm/lib/Demangle/Demangle.cpp
View file

@ -12,6 +12,7 @@
#include "llvm/Demangle/Demangle.h"
#include "llvm/Demangle/StringViewExtras.h"
#include <cctype>
#include <cstdlib>
#include <string_view>
@ -38,6 +39,15 @@ std::string llvm::demangle(std::string_view MangledName) {
}
static bool isItaniumEncoding(std::string_view S) {
if (starts_with(S, "__alloc_token_")) {
S.remove_prefix(sizeof("__alloc_token_") - 1);
if (!S.empty() && std::isdigit(S[0])) {
while (!S.empty() && std::isdigit(S[0]))
S.remove_prefix(1);
if (starts_with(S, "_"))
S.remove_prefix(1);
}
}
// Itanium demangler supports prefixes with 1-4 underscores.
const size_t Pos = S.find_first_not_of('_');
return Pos > 0 && Pos <= 4 && S[Pos] == 'Z';

16
llvm/test/tools/llvm-cxxfilt/alloc-token.test Normal file
View file

@ -0,0 +1,16 @@
## Show that llvm-cxxfilt can handle __alloc_token_ prefixed demangling.
RUN: llvm-cxxfilt __alloc_token__Znwm \
RUN: __alloc_token__Znam \
RUN: __alloc_token_0__Znwm \
RUN: __alloc_token_1__Znam \
RUN: __alloc_token_123__Z3foov \
RUN: __alloc_token_malloc \
RUN: | FileCheck %s
CHECK: operator new(unsigned long) (.alloc_token)
CHECK-NEXT: operator new[](unsigned long) (.alloc_token)
CHECK-NEXT: operator new(unsigned long) (.alloc_token)
CHECK-NEXT: operator new[](unsigned long) (.alloc_token)
CHECK-NEXT: foo() (.alloc_token)
CHECK-NEXT: __alloc_token_malloc