diff --git a/src/heaptrace.cc b/src/heaptrace.cc
index b64bad1..24f3e1e 100644
--- a/src/heaptrace.cc
+++ b/src/heaptrace.cc
@@ -47,7 +47,7 @@ static error_t parse_option(int key, char *arg, struct argp_state *state)
 		break;
 
 	case OPT_top:
-		opts->top = strtol(arg, nullptr, 0);
+		opts->top = std::stoi(arg);
 		break;
 
 	case 's':
diff --git a/src/libheaptrace.cc b/src/libheaptrace.cc
index 72dfd3d..d78f1c6 100644
--- a/src/libheaptrace.cc
+++ b/src/libheaptrace.cc
@@ -90,13 +90,13 @@ __constructor static void heaptrace_init()
 	// setup option values
 	// TODO: create constexpr variables instead of default magic values.
 	env = getenv("HEAPTRACE_NUM_TOP_BACKTRACE");
-	opts.top = env ? strtol(env, nullptr, 0) : 10;
+	opts.top = env ? std::stoi(env) : 10;
 
 	env = getenv("HEAPTRACE_SORT_KEYS");
 	opts.sort_keys = env ? env : "size";
 
 	env = getenv("HEAPTRACE_FLAME_GRAPH");
-	opts.flamegraph = env ? strtol(env, nullptr, 0) : false;
+	opts.flamegraph = env ? std::stoi(env) : false;
 
 	opts.outfile = getenv("HEAPTRACE_OUTFILE");
 	if (opts.outfile) {
diff --git a/src/stacktrace.cc b/src/stacktrace.cc
index 0894fe9..354a30d 100644
--- a/src/stacktrace.cc
+++ b/src/stacktrace.cc
@@ -228,8 +228,8 @@ static std::string get_byte_unit(uint64_t size)
 
 std::string read_statm()
 {
-	int vss, rss, shared;
-	int pagesize_kb = sysconf(_SC_PAGESIZE);
+	long vss, rss, shared;
+	long pagesize_kb = sysconf(_SC_PAGESIZE);
 	std::ifstream fs("/proc/self/statm");
 
 	fs >> vss >> rss >> shared;
@@ -244,7 +244,7 @@ std::string read_statm()
 
 static void print_dump_stackmap_header(const char *sort_key)
 {
-	pr_out("[heaptrace] dump allocation sorted by '%s' for /proc/%d/maps (%s)\n", sort_key,
+	pr_out("[heaptrace] dump allocation sorted by '%s' for /proc/%ld/maps (%s)\n", sort_key,
 	       utils::gettid(), utils::get_comm_name().c_str());
 }
 
@@ -315,7 +315,7 @@ print_dump_stackmap_flamegraph(std::vector<std::pair<stack_trace_t, stack_info_t
 
 		const stack_trace_t &stack_trace = sorted_stack[i].first;
 
-		for (int j = info.stack_depth - 1; j >= 0; j--) {
+		for (size_t j = info.stack_depth - 1; j >= 0; j--) {
 			print_backtrace_symbol_flamegraph(stack_trace[j], semicolon);
 			semicolon = ";";
 		}
diff --git a/src/utils.cc b/src/utils.cc
index 907c492..6f3d8bd 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -34,9 +34,8 @@ std::string get_comm_name(void)
 {
 	std::string comm;
 	std::stringstream ss;
-	int tid = utils::gettid();
 
-	ss << "/proc/" << tid << "/comm";
+	ss << "/proc/" << utils::gettid() << "/comm";
 
 	std::ifstream fs(ss.str());
 	fs >> comm;
@@ -78,7 +77,7 @@ static std::string mmap_string(int val, const struct enum_table *et, int len)
 	/* exact match */
 	for (int i = len - 1; i >= 0; i--) {
 		if (val == et[i].val)
-			return std::string(et[i].str);
+			return { et[i].str };
 	}
 
 	/* OR-ing bit flags */
diff --git a/src/utils.h b/src/utils.h
index 0430032..0b5f3f2 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -23,7 +23,7 @@ typedef std::chrono::duration<uint64_t, std::kilo> kilobytes;
 typedef std::chrono::duration<uint64_t, std::mega> megabytes;
 typedef std::chrono::duration<uint64_t, std::giga> gigabytes;
 
-static int gettid(void)
+static long gettid(void)
 {
 	return syscall(SYS_gettid);
 }