diff --git a/dcc_check_output.c b/dcc_check_output.c
index c6a3b0e..5a662a7 100644
--- a/dcc_check_output.c
+++ b/dcc_check_output.c
@@ -136,7 +136,7 @@ static unsigned char actual_line[ACTUAL_LINE_MAX + 1];
 // position to put next character in above array
 static int n_actual_line;
 // n bytes seen prior to those in above array
-static size_t n_actual_bytes_seen;
+static ssize_t n_actual_bytes_seen;
 static size_t n_actual_lines_seen;
 
 static unsigned char expected_line[ACTUAL_LINE_MAX + 2];
@@ -150,7 +150,7 @@ static void rstrip_line(unsigned char *line, int last_byte_index);
 static void __dcc_compare_output(unsigned char *actual, size_t size) {
 	int expected_bytes_in_line = get_next_expected_line();
 	debug_printf(2, " __dcc_compare_output() n_actual_lines_seen=%d\n", n_actual_lines_seen);
-	for (int i = 0; i < size; i++) {
+	for (size_t i = 0; i < size; i++) {
 		if (max_stdout_bytes && n_actual_line + n_actual_bytes_seen > max_stdout_bytes) {
 			n_actual_lines_seen++;
 			actual_line[n_actual_line] = '\0';
@@ -310,13 +310,13 @@ static void __dcc_compare_output_error(char *reason, int actual_column, int expe
 	snprintf(buffer[3], sizeof buffer[3], "DCC_N_ACTUAL_BYTES_SEEN=%zu", n_actual_bytes_seen);
 	snprintf(buffer[4], sizeof buffer[4], "DCC_ACTUAL_COLUMN=%d", actual_column);
 	snprintf(buffer[5], sizeof buffer[5], "DCC_EXPECTED_COLUMN=%d", expected_column);
-	for (int i = 0; i < sizeof buffer/sizeof buffer[0]; i++)
+	for (unsigned long int i = 0; i < sizeof buffer/sizeof buffer[0]; i++)
 		putenvd(buffer[i]);
 
 	char line_buffer[2][128 + ACTUAL_LINE_MAX];
 	snprintf(line_buffer[0], sizeof line_buffer[0], "DCC_ACTUAL_LINE=%s", actual_line);
 	snprintf(line_buffer[1], sizeof line_buffer[1], "DCC_EXPECTED_LINE=%s", expected_line);
-	for (int i = 0; i < sizeof line_buffer/sizeof line_buffer[0]; i++)
+	for (unsigned long int i = 0; i < sizeof line_buffer/sizeof line_buffer[0]; i++)
 		putenvd(line_buffer[i]);
 	_explain_error();
 }
@@ -358,4 +358,3 @@ static int getenv_boolean(const char *name, int default_value) {
 	return value ? !strchr("0fFnN", *value) : default_value;
 }
 #endif
-
diff --git a/dcc_util.c b/dcc_util.c
index c143f59..d27f149 100644
--- a/dcc_util.c
+++ b/dcc_util.c
@@ -1,5 +1,6 @@
 
 static void launch_valgrind(int argc, char *argv[], char *envp[]) {
+	(void) envp;
 	debug_printf(2, "command=%s\n", "__MONITOR_VALGRIND__");
 #if __N_SANITIZERS__ > 1
 	extern FILE *__real_popen(const char *command, const char *type);
@@ -128,6 +129,7 @@ void __asan_on_error() {
 
 // intercept ASAN explanation
 void _Unwind_Backtrace(void *a, ...) {
+	(void) a;
 	debug_printf(2, "_Unwind_Backtrace\n");
 	_explain_error();
 }
@@ -170,7 +172,7 @@ void __ubsan_on_report(void) {
 	snprintf(buffer[3], sizeof buffer[3], "DCC_UBSAN_ERROR_LINE=%u", OutLine);
 	snprintf(buffer[4], sizeof buffer[4], "DCC_UBSAN_ERROR_COL=%u", OutCol);
 	snprintf(buffer[5], sizeof buffer[5], "DCC_UBSAN_ERROR_MEMORYADDR=%s", OutMemoryAddr);
-	for (int i = 0; i < sizeof buffer/sizeof buffer[0]; i++)
+	for (unsigned long int i = 0; i < sizeof buffer/sizeof buffer[0]; i++)
 		putenv(buffer[i]);
 #endif
 	_explain_error();
@@ -353,7 +355,7 @@ static int debug_printf(int level, const char *format, ...) {
 #include <spawn.h>
 #include <sys/stat.h>
 #include <fcntl.h>
-#include <unistd.h> 
+#include <unistd.h>
 
 int __real_posix_spawn(pid_t *pid, const char *path,
                        const posix_spawn_file_actions_t *file_actions,