[clang] [llvm] [clang][Modules][serialization] Deduplicate source location entries across loaded modules (PR #209795)

[Ayokunle Amodu via cfe-commits]

ayokunle321 wrote:

> I gave this a quick try and it's failing in the build, with an assertion:
> 
> ```
> clang/include/clang/Basic/SourceLocation.h:330: const char *clang::PresumedLoc::getFilename() const: Assertion `isValid()' failed.
> ```
> 
> This happens here: https://github.com/root-project/root/blob/dfe7f8018320b93fab670705226a678442b6a901/core/dictgen/src/BaseSelectionRule.cxx#L41-L59 AFAICT we've never seen (so far) the case where a `SourceLocation` was valid, but then the `PresumedLoc` is invalid...

Thanks for testing. I checked this pre-patch too, and with asserts on I get the same assertion, so I'm fairly sure it's not something the dedup patch introduced. With asserts off it builds through fine with no lingering errors elsewhere.

Did you turn asserts on just for this build, or do you normally build with them on? And if you do build with them on, had you had never hit this before?

@hahnjo 

https://github.com/llvm/llvm-project/pull/209795