[clang] [Clang] Report an error and crash on source location exhaustion in macros (PR #69908)

[Sam McCall via cfe-commits]

================
@@ -663,10 +663,15 @@ SourceManager::createExpansionLocImpl(const ExpansionInfo &Info,
     return SourceLocation::getMacroLoc(LoadedOffset);
   }
   LocalSLocEntryTable.push_back(SLocEntry::get(NextLocalOffset, Info));
-  // FIXME: Produce a proper diagnostic for this case.
-  assert(NextLocalOffset + Length + 1 > NextLocalOffset &&
-         NextLocalOffset + Length + 1 <= CurrentLoadedOffset &&
-         "Ran out of source locations!");
+  if (NextLocalOffset + Length + 1 <= NextLocalOffset ||
+      NextLocalOffset + Length + 1 > CurrentLoadedOffset) {
+    Diag.Report(Info.getSpellingLoc(), diag::err_expansions_too_large);
+    // FIXME: call `noteSLocAddressSpaceUsage` to report details to users.
----------------
sam-mccall wrote:

hm, this makes the diag *significantly* less useful.

I suppose this change is still better than the status quo, but any idea what causes it?

If it's the new LocalSLocEntryTable entry (which seems plausible), it seems you could just move the check above it?

https://github.com/llvm/llvm-project/pull/69908