The isspace/isctrl/etc functions require unsigned char as input

Using signed char is documented to be undefined behavior.

src/lib/processors/htmldocumentprocessor.cpp

@@ -26,7 +26,7 @@ Q_DECLARE_METATYPE(KItinerary::Internal::OwnedPtr<KItinerary::HtmlDocument>)
 
 static bool contentStartsWith(const QByteArray &data, char s)
 {
-    for (const auto c : data) {
+    for (unsigned char c : data) {
         if (std::isspace(c)) {
             continue;
         }
@@ -91,7 +91,7 @@ static QByteArray fixupJson(const QByteArray &data)
     for (int idx = output.indexOf("\",\n"); idx > 0 && idx + 3 < output.size(); idx = output.indexOf("\",\n", idx)) {
         const auto comma = idx + 1;
         idx += 3;
-        while (idx < output.size() && std::isspace(output[idx])) {
+        while (idx < output.size() && std::isspace(static_cast<unsigned char>(output[idx]))) {
             ++idx;
         }
         if (idx < output.size() && output[idx] == '}') {

src/lib/processors/icaldocumentprocessor.cpp

@@ -32,7 +32,7 @@ using namespace KItinerary;
 static bool contentStartsWith(const QByteArray &data, const char *str)
 {
     auto it = data.begin();
-    while (it != data.end() && std::isspace(*it)) {
+    while (it != data.end() && std::isspace(static_cast<unsigned char>(*it))) {
         ++it;
     }
 

src/lib/processors/jsonlddocumentprocessor.cpp

@@ -16,7 +16,7 @@ using namespace KItinerary;
 
 static bool contentStartsWith(const QByteArray &data, char s)
 {
-    for (const auto c : data) {
+    for (unsigned char c : data) {
         if (std::isspace(c)) {
             continue;
         }

src/lib/processors/textdocumentprocessor.cpp

@@ -18,7 +18,7 @@ using namespace KItinerary;
 
 bool TextDocumentProcessor::canHandleData(const QByteArray &encodedData, QStringView fileName) const
 {
-    return std::none_of(encodedData.begin(), encodedData.end(), [](auto c) { return std::iscntrl(c) && !std::isspace(c); })
+    return std::none_of(encodedData.begin(), encodedData.end(), [](unsigned char c) { return std::iscntrl(c) && !std::isspace(c); })
         || fileName.endsWith(QLatin1String(".txt"), Qt::CaseInsensitive);
 }