[libcxx-commits] [libcxxabi] [llvm] [ItaniumDemangle] Strip __alloc_token_ to transparently demangle allocation functions (PR #191048)
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Wed Apr 8 14:44:05 PDT 2026
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-binary-utilities
@llvm/pr-subscribers-libcxxabi
Author: Marco Elver (melver)
<details>
<summary>Changes</summary>
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)`).
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
---
Full diff: https://github.com/llvm/llvm-project/pull/191048.diff
6 Files Affected:
- (modified) libcxxabi/src/demangle/ItaniumDemangle.h (+8)
- (modified) libcxxabi/test/DemangleTestCases.inc (+11)
- (modified) llvm/include/llvm/Demangle/ItaniumDemangle.h (+8)
- (modified) llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc (+11)
- (modified) llvm/lib/Demangle/Demangle.cpp (+10)
- (added) llvm/test/tools/llvm-cxxfilt/alloc-token.test (+16)
``````````diff
diff --git a/libcxxabi/src/demangle/ItaniumDemangle.h b/libcxxabi/src/demangle/ItaniumDemangle.h
index b999438ff2ca8..bbedfb9a72618 100644
--- a/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -6157,8 +6157,16 @@ 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) {
+ if (consumeIf("__alloc_token_")) {
+ const char *Saved = First;
+ if (parseNumber().empty() || !consumeIf('_'))
+ First = Saved;
+ }
+
if (consumeIf("_Z") || consumeIf("__Z")) {
Node *Encoding = getDerived().parseEncoding(ParseParams);
if (Encoding == nullptr)
diff --git a/libcxxabi/test/DemangleTestCases.inc b/libcxxabi/test/DemangleTestCases.inc
index 2721d2aa5504e..1be08d16b18ef 100644
--- a/libcxxabi/test/DemangleTestCases.inc
+++ b/libcxxabi/test/DemangleTestCases.inc
@@ -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__Znam", "operator new[](unsigned long)"},
+{"__alloc_token__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&)"},
+{"__alloc_token__ZnamRKSt9nothrow_t", "operator new[](unsigned long, std::nothrow_t const&)"},
+{"__alloc_token_0__Znwm", "operator new(unsigned long)"},
+{"__alloc_token_1__Znam", "operator new[](unsigned long)"},
+{"__alloc_token_123__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&)"},
+{"__alloc_token__Znwm.llvm.1234", "operator new(unsigned long) (.llvm.1234)"},
+{"__alloc_token_123__Z3foov", "foo()"},
// clang-format on
diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
index 67de123fdbad5..c0378ed88e237 100644
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -6157,8 +6157,16 @@ 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) {
+ if (consumeIf("__alloc_token_")) {
+ const char *Saved = First;
+ if (parseNumber().empty() || !consumeIf('_'))
+ First = Saved;
+ }
+
if (consumeIf("_Z") || consumeIf("__Z")) {
Node *Encoding = getDerived().parseEncoding(ParseParams);
if (Encoding == nullptr)
diff --git a/llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc b/llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc
index 2721d2aa5504e..1be08d16b18ef 100644
--- a/llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc
+++ b/llvm/include/llvm/Testing/Demangle/DemangleTestCases.inc
@@ -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__Znam", "operator new[](unsigned long)"},
+{"__alloc_token__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&)"},
+{"__alloc_token__ZnamRKSt9nothrow_t", "operator new[](unsigned long, std::nothrow_t const&)"},
+{"__alloc_token_0__Znwm", "operator new(unsigned long)"},
+{"__alloc_token_1__Znam", "operator new[](unsigned long)"},
+{"__alloc_token_123__ZnwmRKSt9nothrow_t", "operator new(unsigned long, std::nothrow_t const&)"},
+{"__alloc_token__Znwm.llvm.1234", "operator new(unsigned long) (.llvm.1234)"},
+{"__alloc_token_123__Z3foov", "foo()"},
// clang-format on
diff --git a/llvm/lib/Demangle/Demangle.cpp b/llvm/lib/Demangle/Demangle.cpp
index f0f7eacac98e6..f311caa46b0fb 100644
--- a/llvm/lib/Demangle/Demangle.cpp
+++ b/llvm/lib/Demangle/Demangle.cpp
@@ -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';
diff --git a/llvm/test/tools/llvm-cxxfilt/alloc-token.test b/llvm/test/tools/llvm-cxxfilt/alloc-token.test
new file mode 100644
index 0000000000000..af0cc55f2c454
--- /dev/null
+++ b/llvm/test/tools/llvm-cxxfilt/alloc-token.test
@@ -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)
+CHECK-NEXT: operator new[](unsigned long)
+CHECK-NEXT: operator new(unsigned long)
+CHECK-NEXT: operator new[](unsigned long)
+CHECK-NEXT: foo()
+CHECK-NEXT: __alloc_token_malloc
``````````
</details>
https://github.com/llvm/llvm-project/pull/191048
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