[cfe-dev] Late Parsed Template support for PCH

[Douglas Gregor]

On Jul 24, 2013, at 9:18 AM, Will Wilson <will at indefiant.com> wrote:

> Hi All,
> 
> I've discovered a rather nasty issue with -fdelayed-template-parsing enabled. If this is used to build a PCH all of the stored template tokens are lost leading an incomplete AST when the PCH is used to create the complete TU.
> 
> Is this by design or a missing feature for the serialization code?
> 
> Unfortunately, due to a huge body of MSVC targeted code and a need to use PCH files to maintain acceptable performance I need to make this work seamlessly. The data that would need preserving is currently stored in the Parser and is a map of const FunctionDecl* to LateParsedTemplatedFunction*. The LateParsedTemplatedFunction is essentially a SmallVector of Tokens.
> 
> Before I dive in and attempt to add support for serializing this, is there anything I should know?

It’s a missing feature. One will need to serialize the actual tokens for each of the late-parsed FunctionDecl’s, and be able to lazily deserialize and then parse the tokens when an actual definition is needed.

	- Doug


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