[Lldb-commits] [lldb] a848008 - [lldb] Fixed UB in CPlusPlusLanguage plug-in (#158304)

[via lldb-commits]

Author: Dmitry Vasilyev
Date: 2025-09-12T20:56:21+04:00
New Revision: a848008e1996f8934dee0a297975ac0e6b4200ec

URL: https://github.com/llvm/llvm-project/commit/a848008e1996f8934dee0a297975ac0e6b4200ec
DIFF: https://github.com/llvm/llvm-project/commit/a848008e1996f8934dee0a297975ac0e6b4200ec.diff

LOG: [lldb] Fixed UB in CPlusPlusLanguage plug-in (#158304)

C++11 allows the use of Universal Character Names (UCNs) in identifiers,
including function names.

According to the spec the behavior of std::isalpha(ch) and
std::isalnum(ch) is undefined if the argument's value is neither
representable as unsigned char nor equal to EOF. To use these functions
safely with plain chars (or signed chars), the argument should first be
converted to unsigned char.

Added: 
    

Modified: 
    lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
    lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index 277de8f444828..1f7b8d48d0fc8 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -190,14 +190,16 @@ static bool IsTrivialBasename(const llvm::StringRef &basename) {
   if (basename.size() <= idx)
     return false; // Empty string or "~"
 
-  if (!std::isalpha(basename[idx]) && basename[idx] != '_')
+  if (!std::isalpha(static_cast<unsigned char>(basename[idx])) &&
+      basename[idx] != '_')
     return false; // First character (after removing the possible '~'') isn't in
                   // [A-Za-z_]
 
   // Read all characters matching [A-Za-z_0-9]
   ++idx;
   while (idx < basename.size()) {
-    if (!std::isalnum(basename[idx]) && basename[idx] != '_')
+    if (!std::isalnum(static_cast<unsigned char>(basename[idx])) &&
+        basename[idx] != '_')
       break;
     ++idx;
   }

diff  --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
index 6053d042b29b1..141c5c9a2caf9 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -40,8 +40,10 @@ using namespace lldb_private::formatters;
 static void consumeInlineNamespace(llvm::StringRef &name) {
   // Delete past an inline namespace, if any: __[a-zA-Z0-9_]+::
   auto scratch = name;
-  if (scratch.consume_front("__") && std::isalnum(scratch[0])) {
-    scratch = scratch.drop_while([](char c) { return std::isalnum(c); });
+  if (scratch.consume_front("__") &&
+      std::isalnum(static_cast<unsigned char>(scratch[0]))) {
+    scratch = scratch.drop_while(
+        [](char c) { return std::isalnum(static_cast<unsigned char>(c)); });
     if (scratch.consume_front("::")) {
       // Successfully consumed a namespace.
       name = scratch;