Regex: comment the mutables in CompiledRegex::Instruction and fix their init

src/regex_impl.cc

@@ -757,7 +757,7 @@ private:
     uint32_t push_inst(CompiledRegex::Op op, uint32_t param = 0)
     {
         uint32_t res = m_program.instructions.size();
-        m_program.instructions.push_back({ op, false, false, param });
+        m_program.instructions.push_back({ op, false, 0, param });
         return res;
     }
 

src/regex_impl.hh

@@ -55,6 +55,7 @@ struct CompiledRegex : RefCountable, UseMemoryDomain<MemoryDomain::Regex>
     struct Instruction
     {
         Op op;
+        // Those mutables are used during execution
         mutable bool scheduled;
         mutable uint16_t last_step;
         uint32_t param;