TECH : Error Handling in Libraries: A Case Study

James Henderson
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Event: 2018 US LLVM Developers Meeting

LLVM includes many libraries that are highly useful for a wide range of programs. Even ignoring out-of-tree consumers, there are a huge variety of clients, with different requirements and needs. One concrete example is the LLVMDebugInfoDWARF library, which provides interfaces to extract information about DWARF debug sections from a file. Some clients, such as llvm-dwarfdump, don't want to fail immediately when there is a parsing issue, but may still want to emit an error. On the other hand, LLD uses this library to provide additional information in error messages and may not even want to warn in the event of an issue.

So, what should LLVM libraries do if they encounter a problem when executing a function? Libraries need to provide a rich enough interface that allows getting useful information in the event of an error, without making those errors terminal to the program as a whole. There are already existing mechanisms to do this in LLVM, but using them appropriately requires careful thought.

Using work performed on the DWARF debug line parser earlier this year as an example, this talk will show some of the pitfalls and problems a library developer has to be aware of when handling errors in their code, and will present some good rules of thumb that should be followed.

Duration: 5 Minutes

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