[llvm] [Flang][runtime] Fix RENAME intrinsic, remove trailing blanks (PR #159123)

[Krzysztof Parzyszek via llvm-commits]

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@@ -65,8 +65,20 @@ void RTDEF(Rename)(const Descriptor &path1, const Descriptor &path2,
   char *pathDst{EnsureNullTerminated(
       path2.OffsetElement(), path2.ElementBytes(), terminator)};
 
+  // Trim trailing blanks
+  auto srcTrimPos{TrimTrailingSpaces(pathSrc, path1.ElementBytes())};
+  auto dstTrimPos{TrimTrailingSpaces(pathDst, path2.ElementBytes())};
+  char *srcPathTrim{
+      static_cast<char *>(alloca((srcTrimPos + 1) * sizeof(char)))};
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kparzysz wrote:

sizeof(char) is 1 by definition in C++.

https://github.com/llvm/llvm-project/pull/159123