[flang-commits] [flang] [llvm] [flang] Implement 'F_C_STRING' library function (Fortran 2023) (PR #174474)

[Peter Klausler via flang-commits]

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@@ -843,6 +843,30 @@ void RTDEF(Repeat)(Descriptor &result, const Descriptor &string,
   }
 }
 
+// F_C_STRING - Appends null terminator to create C-compatible string
+// If asis is false, trailing blanks are trimmed first
+void RTDEF(FCString)(Descriptor &result, const Descriptor &string,
+    const Descriptor *asis, const char *sourceFile, int sourceLine) {
+  Terminator terminator{sourceFile, sourceLine};
+  RUNTIME_CHECK(terminator, string.raw().type == CFI_type_char);
+
+  std::size_t chars{string.ElementBytes()};
+  if (!asis || !IsLogicalElementTrue(*asis, nullptr)) {
+    chars = LenTrim(string.OffsetElement<const char>(), chars);
+  }
+  std::size_t resultBytes{chars + 1};
+
+  result.Establish(string.type(), resultBytes, nullptr, 0, nullptr,
+      CFI_attribute_allocatable);
+  RUNTIME_CHECK(terminator, result.Allocate(kNoAsyncObject) == CFI_SUCCESS);
+
+  if (chars > 0) {
+    std::memcpy(result.OffsetElement(), string.OffsetElement(), chars);
+  }
+
+  result.OffsetElement<char>()[chars] = '\0';
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klausler wrote:

That's a weird way to use `OffsetElement`.  Why not use its offset argument?

https://github.com/llvm/llvm-project/pull/174474