diff --git a/example/calc.cc b/example/calc.cc
index a8d9a23..6de3dd0 100644
--- a/example/calc.cc
+++ b/example/calc.cc
@@ -16,7 +16,7 @@ int main(void) {
         %whitespace <- [ \t]*
     )");
 
-    assert((bool)parser == true);
+    assert(static_cast<bool>(parser) == true);
 
     // (3) Setup actions
     parser["Additive"] = [](const SemanticValues& sv) {
diff --git a/lint/peglint.cc b/lint/peglint.cc
index 9b0fa46..14423cc 100644
--- a/lint/peglint.cc
+++ b/lint/peglint.cc
@@ -11,7 +11,7 @@
 
 using namespace std;
 
-bool read_file(const char* path, vector<char>& buff)
+inline bool read_file(const char* path, vector<char>& buff)
 {
     ifstream ifs(path, ios::in | ios::binary);
     if (ifs.fail()) {
@@ -128,13 +128,13 @@ int main(int argc, const char** argv)
                 const peg::any& /*dt*/,
                 size_t len) {
                 auto pos = static_cast<size_t>(s - c.s);
-                if (len != -1) {
+                if (len != static_cast<size_t>(-1)) {
                     pos += len;
                 }
                 string indent;
                 auto level = c.trace_ids.size() - 1;
                 while (level--) { indent += "│"; }
-                auto ret = len != -1 ? "└o " : "└x ";
+                auto ret = len != static_cast<size_t>(-1) ? "└o " : "└x ";
                 std::stringstream choice;
                 if (sv.choice_count() > 0) {
                     choice << " " << sv.choice() << "/" << sv.choice_count();
diff --git a/peglib.h b/peglib.h
index 22fef39..cae4d6d 100644
--- a/peglib.h
+++ b/peglib.h
@@ -3143,7 +3143,6 @@ private:
     };
 
     g["Loop"] = [&](const SemanticValues &sv) {
-      std::pair<size_t, size_t> dummy;
       switch (sv.choice()) {
       case 0: // Option
         return Loop{Loop::Type::opt, std::pair<size_t, size_t>()};
diff --git a/test/test3.cc b/test/test3.cc
index 529e96e..377864e 100644
--- a/test/test3.cc
+++ b/test/test3.cc
@@ -3,13 +3,13 @@
 
 using namespace peg;
 
-bool exact(Grammar& g, const char* d, const char* s) {
+inline bool exact(Grammar& g, const char* d, const char* s) {
     auto n = strlen(s);
     auto r = g[d].parse(s, n);
     return r.ret && r.len == n;
 }
 
-Grammar& make_peg_grammar() {
+inline Grammar& make_peg_grammar() {
     return ParserGenerator::grammar();
 }