[flang-commits] [flang] d7ea606 - [flang] Avoid crash case in provenance mapping

[Peter Klausler via flang-commits]

Author: Peter Klausler
Date: 2022-03-07T11:40:50-08:00
New Revision: d7ea6068e5ad0a75dfd8e6eb09d8f0d26df755fc

URL: https://github.com/llvm/llvm-project/commit/d7ea6068e5ad0a75dfd8e6eb09d8f0d26df755fc
DIFF: https://github.com/llvm/llvm-project/commit/d7ea6068e5ad0a75dfd8e6eb09d8f0d26df755fc.diff

LOG: [flang] Avoid crash case in provenance mapping

When a contiguous range of a cooked character stream is being
mapped to a range of source provenance, the code was assuming
that the "end()" position of the input range -- being the character
immediately after the range -- would also follow the range's
source provenance.  This isn't always the case.

Modify the code to work with the true last character of the
input range (at end()-1) and to also cope with cases when that
last position truly maps to an earlier provenance, which can happen
when the prescanner has inserted a space into the cooked character
stream.

Differential Revision: https://reviews.llvm.org/D121124

Added: 
    

Modified: 
    flang/lib/Parser/provenance.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Parser/provenance.cpp b/flang/lib/Parser/provenance.cpp
index 27cc1ebf84f89..e2364d3f8a562 100644
--- a/flang/lib/Parser/provenance.cpp
+++ b/flang/lib/Parser/provenance.cpp
@@ -435,11 +435,15 @@ std::optional<ProvenanceRange> CookedSource::GetProvenanceRange(
     return std::nullopt;
   }
   ProvenanceRange first{provenanceMap_.Map(cookedRange.begin() - &data_[0])};
-  if (cookedRange.size() <= first.size()) {
+  if (cookedRange.size() <= first.size()) { // always true when empty
     return first.Prefix(cookedRange.size());
   }
-  ProvenanceRange last{provenanceMap_.Map(cookedRange.end() - &data_[0])};
-  return {ProvenanceRange{first.start(), last.start() - first.start()}};
+  ProvenanceRange last{provenanceMap_.Map(cookedRange.end() - 1 - &data_[0])};
+  if (first.start() <= last.start()) {
+    return {ProvenanceRange{first.start(), last.start() - first.start() + 1}};
+  } else {
+    return std::nullopt;
+  }
 }
 
 std::optional<CharBlock> CookedSource::GetCharBlock(