Security: replace operator[] with at

For std::string and std::vector, replace operator[] with at.  This was
done using an automated process.  See README.hardening for details.

1 files changed, 1 insertions, 1 deletions

diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index de3099d2..cf455061 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -201,7 +201,7 @@ QUtil::hex_encode(std::string const& input)
     for (unsigned int i = 0; i < input.length(); ++i)
     {
         result += QUtil::int_to_string_base(
-            static_cast<int>(static_cast<unsigned char>(input[i])), 16, 2);
+            static_cast<int>(static_cast<unsigned char>(input.at(i))), 16, 2);
     }
     return result;
 }