From 942e458bf5267402843965876216d44d69c34d03 Mon Sep 17 00:00:00 2001
From: Alhuda Khan <admin@research.digiscrypt.com>
Date: Sun, 11 Oct 2026 23:54:28 +0530
Subject: [PATCH] cast to unsigned char for ctype calls on signed-char input

---
 src/Client.cpp     | 2 +-
 src/IRCNetwork.cpp | 2 +-
 src/Message.cpp    | 5 +++--
 src/User.cpp       | 5 +++--
 src/ZNCString.cpp  | 4 ++--
 5 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/Client.cpp b/src/Client.cpp
index acb7e8b6..aa9c0896 100644
--- a/src/Client.cpp
+++ b/src/Client.cpp
@@ -792,7 +792,7 @@ bool CClient::IsValidIdentifier(const CString& sIdentifier) {
 
     const char* p = sIdentifier.c_str();
     while (*p) {
-        if (*p != '_' && *p != '-' && !isalnum(*p)) {
+        if (*p != '_' && *p != '-' && !isalnum((unsigned char)*p)) {
             return false;
         }
 
diff --git a/src/IRCNetwork.cpp b/src/IRCNetwork.cpp
index 767210dd..def087fd 100644
--- a/src/IRCNetwork.cpp
+++ b/src/IRCNetwork.cpp
@@ -117,7 +117,7 @@ bool CIRCNetwork::IsValidNetwork(const CString& sNetwork) {
 
     const char* p = sNetwork.c_str();
     while (*p) {
-        if (*p != '_' && *p != '-' && !isalnum(*p)) {
+        if (*p != '_' && *p != '-' && !isalnum((unsigned char)*p)) {
             return false;
         }
 
diff --git a/src/Message.cpp b/src/Message.cpp
index 71369a7f..fec944f8 100644
--- a/src/Message.cpp
+++ b/src/Message.cpp
@@ -254,8 +254,9 @@ void CMessage::InitTime() {
 }
 
 void CMessage::InitType() {
-    if (m_sCommand.length() == 3 && isdigit(m_sCommand[0]) &&
-        isdigit(m_sCommand[1]) && isdigit(m_sCommand[2])) {
+    if (m_sCommand.length() == 3 && isdigit((unsigned char)m_sCommand[0]) &&
+        isdigit((unsigned char)m_sCommand[1]) &&
+        isdigit((unsigned char)m_sCommand[2])) {
         m_eType = Type::Numeric;
     } else if (m_sCommand.Equals("PRIVMSG")) {
         CString sParam = GetParam(1);
diff --git a/src/User.cpp b/src/User.cpp
index ded6d19a..8eb50b17 100644
--- a/src/User.cpp
+++ b/src/User.cpp
@@ -921,7 +921,8 @@ bool CUser::IsValidUserName(const CString& sUsername) {
     }
 
     while (*p) {
-        if (*p != '@' && *p != '.' && *p != '-' && *p != '_' && !isalnum(*p)) {
+        if (*p != '@' && *p != '.' && *p != '-' && *p != '_' &&
+            !isalnum((unsigned char)*p)) {
             return false;
         }
 
@@ -1402,7 +1403,7 @@ bool CUser::SetStatusPrefix(const CString& s) {
 bool CUser::SetLanguage(const CString& s) {
     // They look like ru-RU
     for (char c : s) {
-        if (isalpha(c) || c == '-' || c == '_') {
+        if (isalpha((unsigned char)c) || c == '-' || c == '_') {
         } else {
             return false;
         }
diff --git a/src/ZNCString.cpp b/src/ZNCString.cpp
index c30469b9..c61d96ce 100644
--- a/src/ZNCString.cpp
+++ b/src/ZNCString.cpp
@@ -220,7 +220,7 @@ bool CString::WildCmp(const CString& sWild, CaseSensitivity cs) const {
 CString& CString::MakeUpper() {
     for (char& c : *this) {
         // TODO use unicode
-        c = (char)toupper(c);
+        c = (char)toupper((unsigned char)c);
     }
 
     return *this;
@@ -229,7 +229,7 @@ CString& CString::MakeUpper() {
 CString& CString::MakeLower() {
     for (char& c : *this) {
         // TODO use unicode
-        c = (char)tolower(c);
+        c = (char)tolower((unsigned char)c);
     }
 
     return *this;