================
@@ -832,13 +835,11 @@ FileID
SourceManager::getFileIDLocal(SourceLocation::UIntTy SLocOffset) const {
unsigned LessIndex = 0;
// upper bound of the search range.
unsigned GreaterIndex = LocalSLocEntryTable.size();
- if (LastFileIDLookup.ID >= 0) {
- // Use the LastFileIDLookup to prune the search space.
- if (LocalSLocEntryTable[LastFileIDLookup.ID].getOffset() < SLocOffset)
- LessIndex = LastFileIDLookup.ID;
- else
- GreaterIndex = LastFileIDLookup.ID;
- }
+ // Use the LastFileIDLookup to prune the search space.
+ if (LastLookupStartOffset < SLocOffset)
+ LessIndex = LastFileIDLookup.ID;
----------------
hokein wrote:
`ID` cannot be negative here — `LastFileIDLookup` is only a cache for the
**local** SLoc entry table, not the `Loaded` one.
When there is no cached entry yet, the state is:
* Both `LastLookupStartOffset` and `LastLookupEndOffset` are `0`.
* `LastFileIDLookup` is initialized to an invalid value (i.e.,
`LastFileIDLookup.ID` is `0`).
The only possible bug here would be if `SLocOffset` were `0`. In that case,
`GreaterIndex` would be set to `0`, and the subsequent `--GreaterIndex;` would
cause an out-of-bounds access on `LocalSLocEntryTable`.
However, this can't happen in practice: `SLocOffset` is guaranteed to be
non-zero in this function, as ensured by the guard here:
[https://github.com/llvm/llvm-project/blob/main/clang/lib/Basic/SourceManager.cpp#L789-L790](https://github.com/llvm/llvm-project/blob/main/clang/lib/Basic/SourceManager.cpp#L789-L790)
I’ve also added some assertions to clarify this in the code.
https://github.com/llvm/llvm-project/pull/146782
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