Switch back to std::string in patch to fix a use-after-free

[rtldg]

SymbolString returns a const char * so our auto name is a const char *. If the name was successfully demangled, then we assign name to demangled, and then immediately after free(demangled).

Switching back to using std::string resolves this since that duplicates the strings.

Popped up after #35 and I only encountered it because of a non-default memory-allocator.

[Kenzzer]

Took me a lot of back and forth to grasp the situation given the PR changes and one line wording, so I'm providing some clarifications below.

I disagree with one of the statements from the post

then we assign name to demangled, and then immediately after free(demangled)

This isn't what's happening, name isn't assigned to demangled.
demangled gets assigned whatever result stems from abi::__cxa_demangle(name.c_str(), nullptr, nullptr, &status)

But in any case this isn't what we should focus on, after mulling it over for a few minutes I realised the PR meant line 30 of the patch (which doesn't appear in the changes)

name = demangled;

name gets assigned demangled, and like said in OP demangled gets freed immediately in the line below so name has a dangling pointer.

This got me confused for a while because abi::__cxa_demangle, that get assigned to demangled, allocates memory for you. So I was focusing on the wrong line this whole time lol. I'm putting this here as a clarification note for history diggers.

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Putting all of this aside, this is awesome work as always @rtldg and you're in all honesty a saviour. This PR demonstrates that extra scrutiny should be put on the breakpad patches, especially the older ones, everytime we move forward the submodule version.

[Kenzzer]

Happy new year, and first commit of 2026 for accelerator. Congratulations, and thanks again!