[PATCH] D133009: [libclang] Fix conversion from `StringRef` to `CXString`

[Egor Zhdan via Phabricator via cfe-commits]

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`CXString createRef(StringRef String)` used to return an invalid string when invoked with some empty strings:

If a `StringRef` holds a non-nullptr pointer, for instance, pointing into contents of a larger string, and has a zero length, `createRef` previously returned the entire larger string, ignoring the fact that the actual string passed to it as a param is empty.

This was discovered when invoking `c-index-test` to dump the contents of documentation comments, in case the comment contains an empty HTML attribute, such as `src=""`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133009

Files:
  clang/test/Index/comment-to-html-xml-conversion.cpp
  clang/tools/libclang/CXString.cpp


Index: clang/tools/libclang/CXString.cpp
===================================================================
--- clang/tools/libclang/CXString.cpp
+++ clang/tools/libclang/CXString.cpp
@@ -78,13 +78,22 @@
 }
 
 CXString createRef(StringRef String) {
+  if (!String.data())
+    return createNull();
+
+  // If the string is empty, it might point to a position in another string
+  // while having zero length. Make sure we don't create a reference to the
+  // larger string.
+  if (String.empty())
+    return createEmpty();
+
   // If the string is not nul-terminated, we have to make a copy.
 
   // FIXME: This is doing a one past end read, and should be removed! For memory
   // we don't manage, the API string can become unterminated at any time outside
   // our control.
 
-  if (!String.empty() && String.data()[String.size()] != 0)
+  if (String.data()[String.size()] != 0)
     return createDup(String);
 
   CXString Result;
Index: clang/test/Index/comment-to-html-xml-conversion.cpp
===================================================================
--- clang/test/Index/comment-to-html-xml-conversion.cpp
+++ clang/test/Index/comment-to-html-xml-conversion.cpp
@@ -744,6 +744,15 @@
 // CHECK-NEXT:         (CXComment_Text Text=[ ] IsWhitespace)
 // CHECK-NEXT:         (CXComment_InlineCommand CommandName=[anchor] RenderAnchor Arg[0]=A)))]
 
+/// Aaa ccc<img src="">
+void comment_to_html_conversion_40();
+
+// CHECK: comment-to-html-xml-conversion.cpp:[[@LINE-2]]:6: FunctionDecl=comment_to_html_conversion_40:{{.*}} FullCommentAsHTML=[<p class="para-brief"> Aaa ccc<img src></p>] FullCommentAsXML=[<Function file="{{[^"]+}}comment-to-html-xml-conversion.cpp" line="[[@LINE-2]]" column="6"><Name>comment_to_html_conversion_40</Name><USR>c:@F at comment_to_html_conversion_40#</USR><Declaration>void comment_to_html_conversion_40()</Declaration><Abstract><Para> Aaa ccc<rawHTML><![CDATA[<img src>]]></rawHTML></Para></Abstract></Function>]
+// CHECK-NEXT:  CommentAST=[
+// CHECK-NEXT:    (CXComment_FullComment
+// CHECK-NEXT:       (CXComment_Paragraph
+// CHECK-NEXT:         (CXComment_Text Text=[ Aaa ccc])
+// CHECK-NEXT:         (CXComment_HTMLStartTag Name=[img] Attrs: src=)
 
 /// Aaa.
 class comment_to_xml_conversion_01 {


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