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[flang] fix possible iterator underflow #115754

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4 changes: 2 additions & 2 deletions flang/lib/Semantics/semantics.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -415,12 +415,12 @@ auto SemanticsContext::SearchScopeIndex(parser::CharBlock source)
if (!scopeIndex_.empty()) {
auto iter{scopeIndex_.upper_bound(source)};
auto begin{scopeIndex_.begin()};
do {
while (iter != begin) {
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@kparzysz kparzysz Nov 27, 2024

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This will skip the loop when iter == begin, which still points to a valid element.

This is actually ok.

--iter;
if (iter->first.Contains(source)) {
return iter;
}
} while (iter != begin);
}
}
return scopeIndex_.end();
}
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