Fix unnecessary copies in auto iter (fixes #426)

Also switch to colon-style iteration in some cases. Thanks to Dean
Scarff for drawing this to my attention after detecting some
unnecessary copies with
https://clang.llvm.org/extra/clang-tidy/checks/performance-for-range-copy.html

1 files changed, 2 insertions, 3 deletions

diff --git a/libqpdf/QPDFCryptoProvider.cc b/libqpdf/QPDFCryptoProvider.cc
index b375498d..5f65da3b 100644
--- a/libqpdf/QPDFCryptoProvider.cc
+++ b/libqpdf/QPDFCryptoProvider.cc
@@ -110,10 +110,9 @@ QPDFCryptoProvider::getRegisteredImpls()
 {
     std::set<std::string> result;
     QPDFCryptoProvider& p = getInstance();
-    for (auto iter = p.m->providers.begin(); iter != p.m->providers.end();
-         ++iter)
+    for (auto const& iter: p.m->providers)
     {
-        result.insert((*iter).first);
+        result.insert(iter.first);
     }
     return result;
 }