Merge pull request #5506 from thomasspriggs/tas/fix_windows_jbmc_unicode

Fix JBMC crash on windows in `NondetEnumOpaqueReturn` test

Author: NlightNFotis

src/util/string_utils.cpp

@@ -156,13 +156,20 @@ std::string escape_non_alnum(const std::string &to_escape)
   std::ostringstream escaped;
   for(auto &ch : to_escape)
   {
+    // `ch` may have a negative value in the case of utf-8 encodings of
+    // characters above unicode code point 127. The following line maps these
+    // negative values to positive values in the 128-255 range, using a
+    // `static_cast`. This is neccessary in order to avoid undefined behaviour
+    // in `isalnum`. The positive values are then stored in an integer using a
+    // widening initialisation so that the stream insertion operator prints them
+    // as numbers rather than characters.
+    const int uch{static_cast<unsigned char>(ch)};
     if(ch == '_')
       escaped << "__";
-    else if(isalnum(ch))
+    else if(isalnum(uch))
       escaped << ch;
     else
-      escaped << '_' << std::hex << std::setfill('0') << std::setw(2)
-              << (unsigned int)ch;
+      escaped << '_' << std::hex << std::setfill('0') << std::setw(2) << uch;
   }
   return escaped.str();
 }

unit/Makefile

@@ -119,6 +119,7 @@ SRC += analyses/ai/ai.cpp \
        util/string2int.cpp \
        util/structured_data.cpp \
        util/string_utils/capitalize.cpp \
+       util/string_utils/escape_non_alnum.cpp \
        util/string_utils/join_string.cpp \
        util/string_utils/split_string.cpp \
        util/string_utils/strip_string.cpp \