[PATCH] D53931: TableGen: Fix ASAN error

[Simon Tatham via Phabricator via llvm-commits]

simon_tatham added inline comments.


================
Comment at: utils/TableGen/SearchableTableEmitter.cpp:168
-                        "' too large to search");
-      return "uint" + utostr(NumBits) + "_t";
     } else if (Field.Enum || Field.IsIntrinsic || Field.IsInstruction)
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nhaehnle wrote:
> kparzysz wrote:
> > How does the problem actually occur?  utostr returns a temporary std::string which should exist until the sum is constructed.  What object is used-after-scope?
> Must be some temporary object (the ASAN dump calls it "unknown"). To be honest, I was surprised about it as well, but I don't really have the time to dig into it further.
I just did have a go at digging into it, because the line numbers in the backtrace make sense with respect to that header file on my nearest 18.10 box.

But it's happening in a move constructor for the type `_Alloc_hider` which is internal to libstdc++ (and contained in a string that's being move-constructed in turn by the `operator+` doing one of the concatenations). At the point where I started having to understand someone else's C++ library internals I decided I didn't have the time either :-)


Repository:
  rL LLVM

https://reviews.llvm.org/D53931