[SizzleUnrlsd]

Fixes #240

Problem

ctrace_tools::isMangled and ctrace_tools::demangle read a symbol with the C++ runtime's abi::__cxa_demangle only. A runtime whose demangler predates a mangling rejects the symbol, and every caller then shows the symbol: diagnostics through formatFunctionNameForMessage, the function filters and the stack report. A C++23 explicit object member function, _ZNH6Reader4peekERKS_Pi, is one: macOS 14's runtime and Ubuntu 22.04's (libstdc++ of GCC 11) reject it, while Ubuntu 24.04's, macOS 27's and LLVM 20's demangler read it.

Change

src/mangle.cpp: isMangled and demangle share one reading. The runtime's __cxa_demangle comes first, then LLVM's llvm::itaniumDemangle when the runtime's fails. The fallback is generic: it does not depend on the platform or on the symbol. A name that neither reads stays a plain name. Where the runtime already reads a symbol, nothing changes.

include/mangle.hpp: isMangled becomes a declaration taking a std::string_view, defined in mangle.cpp. The StringLike concept, which only this template used, goes. LLVMDemangle already comes with LLVMSupport, so no dependency is added.

Tests

testSymbolDemangling (test/unit/analyzer_module_unit_tests.cpp) covers the explicit object member's symbol: it is recognized as mangled, shown demangled, and named demangled in a message. Three controls cover a member's symbol, a C function's name, and a name that no demangler reads.

	Ubuntu 22.04, libstdc++ of GCC 11	macOS 27
main (f846712), without the fix	the three explicit object checks fail; the controls pass	all pass: its runtime reads the symbol
with the fix	all pass	all pass

The test was compiled on Ubuntu 22.04 as the unit test file has it, against the real src/mangle.cpp and src/analysis/AnalyzerUtils.cpp, in a Docker image with LLVM 20 that keeps GCC 11's runtime. On macos-14, #239's CI shows the defect through the fixture const-suggestion-explicit-object.cpp of #217's branch.

Validation

At 270955e, on macOS (LLVM 20): built without warning; the unit tests and the ownership tests pass; the suite, as CI runs it, passes 2415/2415, as on main.

CI and code scanning

• CI on 270955e (merge ref 32771e6, into main at f846712): every check passes. On macos-14 (Xcode 15.4), whose runtime does not read _ZNH6Reader4peekERKS_Pi, the six checks of testSymbolDemangling pass, and the suite passes 2415/2415.
• Code scanning: coretrace-stack-analyzer reported 71 results there and coretrace-concurrency-analyzer none, as on main at f846712. New alerts: none. The 66 alerts open on refs/pull/241/merge are the 66 open on main, alert for alert.