[flang-commits] [PATCH] D154750: [flang][runtime] Fix BACKSPACE over an empty record

[Peter Klausler via Phabricator via flang-commits]

klausler created this revision.
klausler added a reviewer: vzakhari.
klausler added a project: Flang.
Herald added subscribers: sunshaoce, jdoerfert.
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klausler requested review of this revision.

The implementation of BACKSPACE on a variable-length sequential formatted
file has a bug that prevents it from working on an empty record.


https://reviews.llvm.org/D154750

Files:
  flang/runtime/unit.cpp


Index: flang/runtime/unit.cpp
===================================================================
--- flang/runtime/unit.cpp
+++ flang/runtime/unit.cpp
@@ -843,7 +843,7 @@
 // There's no portable memrchr(), unfortunately, and strrchr() would
 // fail on a record with a NUL, so we have to do it the hard way.
 static const char *FindLastNewline(const char *str, std::size_t length) {
-  for (const char *p{str + length}; p-- > str;) {
+  for (const char *p{str + length}; p >= str; p--) {
     if (*p == '\n') {
       return p;
     }


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