diff --git a/src/cmd/yacc/.gitignore b/src/cmd/yacc/.gitignore
new file mode 100644
index 0000000..d0848f9
--- /dev/null
+++ b/src/cmd/yacc/.gitignore
@@ -0,0 +1 @@
+yacc
diff --git a/src/share/zoneinfo/ialloc.c b/src/share/zoneinfo/ialloc.c
index 83a0932..c583a55 100644
--- a/src/share/zoneinfo/ialloc.c
+++ b/src/share/zoneinfo/ialloc.c
@@ -16,7 +16,7 @@
 #endif /* !MAL */
 
 char *
-imalloc(n)
+imalloc(int n)
 {
 #ifdef MAL
 	register char *	result;
@@ -33,7 +33,7 @@ imalloc(n)
 }
 
 char *
-icalloc(nelem, elsize)
+icalloc(int nelem, int elsize)
 {
 	if (nelem == 0 || elsize == 0)
 		nelem = elsize = 1;
@@ -41,8 +41,7 @@ icalloc(nelem, elsize)
 }
 
 char *
-irealloc(pointer, size)
-char *	pointer;
+irealloc(char *pointer, int size)
 {
 	if (NULLMAL(pointer))
 		return imalloc(size);
diff --git a/tools/virtualmips/Makefile b/tools/virtualmips/Makefile
index bd41135..76900f4 100644
--- a/tools/virtualmips/Makefile
+++ b/tools/virtualmips/Makefile
@@ -16,7 +16,7 @@ CFLAGS		= -DSIM_PIC32 -DPIC32MX7 -DMAX32
 #CFLAGS		= -DSIM_PIC32 -DPIC32MX7 -DUBW32
 
 CC          = gcc -g
-CFLAGS		+= -Wall -MT $@ -MD -MP -MF .deps/$*.dep -I/opt/local/include -I/opt/local/include/libelf
+CFLAGS		+= -Wall -Werror -MT $@ -MD -MP -MF .deps/$*.dep -I/opt/local/include -I/opt/local/include/libelf
 LIBS		= -lpthread -lelf
 
 ifneq ($(wildcard /usr/lib/librt.a),)
diff --git a/tools/virtualmips/mips.c b/tools/virtualmips/mips.c
index 6038b7a..d534e2a 100644
--- a/tools/virtualmips/mips.c
+++ b/tools/virtualmips/mips.c
@@ -310,14 +310,14 @@ int fastcall mips_update_irq_flag (cpu_mips_t * cpu)
 }
 
 #if SIM_PIC32
-static void print_arg (val) {
+static void print_arg (int val) {
     if (val & 0xff000000)
         printf ("%08x", val);
     else
         printf ("%u", val);
 }
 
-static void print_args (narg, arg0, arg1, arg2, arg3, arg4, arg5)
+static void print_args (int narg, int arg0, int arg1, int arg2, int arg3, int arg4, int arg5)
 {
     print_arg (arg0);
     if (narg > 1) { printf (", "); print_arg (arg1); }
diff --git a/tools/virtualmips/pic32_dev_adc.c b/tools/virtualmips/pic32_dev_adc.c
index 4c21088..a3ebe67 100644
--- a/tools/virtualmips/pic32_dev_adc.c
+++ b/tools/virtualmips/pic32_dev_adc.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_bmxcon.c b/tools/virtualmips/pic32_dev_bmxcon.c
index 20f6052..13f79c3 100644
--- a/tools/virtualmips/pic32_dev_bmxcon.c
+++ b/tools/virtualmips/pic32_dev_bmxcon.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_dmacon.c b/tools/virtualmips/pic32_dev_dmacon.c
index cb52404..d1a37a4 100644
--- a/tools/virtualmips/pic32_dev_dmacon.c
+++ b/tools/virtualmips/pic32_dev_dmacon.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_gpio.c b/tools/virtualmips/pic32_dev_gpio.c
index d6dbccc..146ecce 100644
--- a/tools/virtualmips/pic32_dev_gpio.c
+++ b/tools/virtualmips/pic32_dev_gpio.c
@@ -97,7 +97,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_intcon.c b/tools/virtualmips/pic32_dev_intcon.c
index fe8c222..cf47b4c 100644
--- a/tools/virtualmips/pic32_dev_intcon.c
+++ b/tools/virtualmips/pic32_dev_intcon.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_prefetch.c b/tools/virtualmips/pic32_dev_prefetch.c
index 1fb3133..e74a773 100644
--- a/tools/virtualmips/pic32_dev_prefetch.c
+++ b/tools/virtualmips/pic32_dev_prefetch.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_rtcc.c b/tools/virtualmips/pic32_dev_rtcc.c
index 93cfcf3..f537897 100644
--- a/tools/virtualmips/pic32_dev_rtcc.c
+++ b/tools/virtualmips/pic32_dev_rtcc.c
@@ -26,7 +26,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_spi.c b/tools/virtualmips/pic32_dev_spi.c
index b4bf664..22c6b7b 100644
--- a/tools/virtualmips/pic32_dev_spi.c
+++ b/tools/virtualmips/pic32_dev_spi.c
@@ -48,7 +48,7 @@ extern cpu_mips_t *current_cpu;
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */
diff --git a/tools/virtualmips/pic32_dev_timer.c b/tools/virtualmips/pic32_dev_timer.c
index 1857a43..f0ea16d 100644
--- a/tools/virtualmips/pic32_dev_timer.c
+++ b/tools/virtualmips/pic32_dev_timer.c
@@ -44,7 +44,7 @@ static const int timer_scale[8] = {
 /*
  * Perform an assign/clear/set/invert operation.
  */
-static inline unsigned write_op (a, b, op)
+static inline unsigned write_op (int a, int b, int op)
 {
     switch (op & 0xc) {
     case 0x0:           /* Assign */