only allow builtin iconv support

Author: abhina-sree

llvm/cmake/config-ix.cmake

@@ -283,7 +283,9 @@ if(LLVM_ENABLE_ICONV)
   else()
     find_package(Iconv)
   endif()
-  set(HAVE_ICONV ${Iconv_FOUND})
+  if(Iconv_FOUND AND Iconv_IS_BUILT_IN)
+    set(HAVE_ICONV 1)
+  endif()
 endif()
 
 # function checks

llvm/lib/Support/CMakeLists.txt

@@ -302,14 +302,6 @@ if(ICU_FOUND)
   PRIVATE
   ${ICU_LIBRARIES}
   )
-else()
-  # Link iconv library if it is an external library.
-  if(Iconv_FOUND AND NOT Iconv_IS_BUILT_IN)
-    target_link_libraries(LLVMSupport
-    PRIVATE
-    ${Iconv_LIBRARIES}
-    )
-  endif()
 endif()
 
 set(llvm_system_libs ${system_libs})

llvm/lib/Support/CharSet.cpp

@@ -215,7 +215,7 @@ std::error_code CharSetConverterIconv::convert(StringRef Source,
   // Setup the output. We directly write into the SmallVector.
   Result.resize_for_overwrite(Source.size());
   size_t Capacity = Result.capacity();
-  char *Output = InputLength ? static_cast<char *>(Result.data()) : nullptr;
+  char *Output = static_cast<char *>(Result.data());
   size_t OutputLength = Capacity;
 
   size_t Ret;
@@ -265,7 +265,7 @@ std::error_code CharSetConverterIconv::flush() const {
 
 std::error_code
 CharSetConverterIconv::flush(SmallVectorImpl<char> &Result) const {
-  return convert(nullptr, Result);
+  return convert("", Result, /*ShouldAutoFlush=*/true);
 }
 
 #endif // HAVE_ICONV