Enable clang-tidy narrowing conversions (#2564)

.clang-tidy

@@ -24,7 +24,6 @@ Checks: '
     -cppcoreguidelines-avoid-non-const-global-variables,
     -cppcoreguidelines-init-variables,
     -cppcoreguidelines-macro-usage,
-    -cppcoreguidelines-narrowing-conversions,
     -cppcoreguidelines-no-malloc,
     -cppcoreguidelines-owning-memory,
     -cppcoreguidelines-pro-bounds-array-to-pointer-decay,
@@ -80,5 +79,6 @@ Checks: '
     -readability-simplify-boolean-expr,
     -readability-suspicious-call-argument'
 CheckOptions:
+    cppcoreguidelines-narrowing-conversions.WarnOnEquivalentBitWidth: 'false'
     readability-implicit-bool-conversion.AllowIntegerConditions: 'true'
     readability-implicit-bool-conversion.AllowPointerConditions: 'true'

src/curl_multi.cpp

@@ -161,9 +161,9 @@ int S3fsMultiCurl::MultiPerform()
     for(const auto &thread_id : completed_tids){
         auto it = threads.find(thread_id);
         it->second.first.join();
-        long int int_retval = it->second.second.get();
+        auto int_retval = it->second.second.get();
         if (int_retval && !(int_retval == -ENOENT && isMultiHead)) {
-            S3FS_PRN_WARN("thread terminated with non-zero return code: %ld", int_retval);
+            S3FS_PRN_WARN("thread terminated with non-zero return code: %d", int_retval);
             result = int_retval;
         }
         threads.erase(it);

src/string_util.cpp

@@ -99,7 +99,7 @@ std::string lower(std::string s)
 {
     // change each character of the std::string to lower case
     for(size_t i = 0; i < s.length(); i++){
-        s[i] = tolower(s[i]);
+        s[i] = static_cast<char>(tolower(s[i]));
     }
     return s;
 }

src/test_string_util.cpp

@@ -130,7 +130,7 @@ void test_wtf8_encoding()
     std::string utf8("Hyld\xc3\xbdpi \xc3\xbej\xc3\xb3\xc3\xb0""f\xc3\xa9lagsins vex \xc3\xbar k\xc3\xa6rkomnu b\xc3\xb6li \xc3\xad \xc3\xa1st");
     std::string cp1252("Hyld\xfdpi \xfej\xf3\xf0""f\xe9lagsins vex \xfar k\xe6rkomnu b\xf6li \xed \xe1st");
     std::string broken = utf8;
-    broken[14] = 0x97;
+    broken[14] = '\x97';
     std::string mixed = ascii + utf8 + cp1252;
 
     ASSERT_EQUALS(s3fs_wtf8_encode(ascii), ascii);