[Syntax] Fix use-after-free in SyntaxSerialization

[harlanhaskins]

The ASAN build caught a use-after-free because the StringRef passed into the JSON output for TriviaPiece was destroyed before the outputting happened. Instead, explicitly copy the OwnedString first. Instead, ensure the string outlives the raw syntax tree by moving the CompilerInstance out of getSyntaxTree.

[harlanhaskins]

@swift-ci please ASAN test

[harlanhaskins]

@swift-ci please ASAN test

[huonw]

Doesn't this mean the copy of the string leaks? Either that or the copy is destroyed at the end of the statement and asan will fail too?

[harlanhaskins]

Yep. I think the main issue is that this string owned by the SourceManager and not the RawSyntax tree.

A more permanent fix would be to ensure the SourceManager lives as long as the RawSyntax tree here.

[harlanhaskins]

@swift-ci please ASAN test

[harlanhaskins]

Passed ASAN locally.

@swift-ci please ASAN test

[huonw]

It would be nice to squash the two commits before merging, so that the copying isn't done and then immediately undone.

[harlanhaskins]

I squashed those changes 👍

@swift-ci please smoke test and merge

[CodaFi]

@swift-ci please smoke test and merge

[harlanhaskins]

Uh... @shahmishal:

/home/buildnode/disk2/workspace/swift-PR-Linux-smoke-test/branch-master/swift/utils/build-script-impl: line 261: 18071 Segmentation fault      "$@"

[harlanhaskins]

This was after building Foundation.

[harlanhaskins]

In the meantime, what's one more test?

@swift-ci please smoke test and merge