diff --git a/examples/crt.c b/examples/crt.c
index e9082703fc..f9af8abef0 100644
--- a/examples/crt.c
+++ b/examples/crt.c
@@ -22,7 +22,7 @@
 
 int main(int argc, char* argv[])
 {
-    slong i, bit_bound;
+    slong bit_bound;
     mp_limb_t prime, res;
     fmpz_t x, y, prod;
 
@@ -43,7 +43,7 @@ int main(int argc, char* argv[])
     fmpz_one(prod);
 
     prime = 0;
-    for (i = 0; fmpz_bits(prod) < bit_bound; i++)
+    while(fmpz_bits(prod) < bit_bound)
     {
         prime = n_nextprime(prime, 0);
         res = fmpz_fdiv_ui(x, prime);
diff --git a/examples/dft.c b/examples/dft.c
index f8f9bf5398..eb373cae93 100644
--- a/examples/dft.c
+++ b/examples/dft.c
@@ -172,7 +172,7 @@ benchmark_DFT(slong N, int input, int verbose, slong qqbar_limit, slong gb, ca_c
     ca_clear(t, ctx);
 }
 
-void usage()
+void usage(void)
 {
     printf("usage: dft [-verbose] [-input i] [-limit B] [-timing T] [-nogb] N\n");
 }
diff --git a/examples/fpwrap.c b/examples/fpwrap.c
index 79f4951392..71fb51f585 100644
--- a/examples/fpwrap.c
+++ b/examples/fpwrap.c
@@ -2,7 +2,7 @@
 
 #include "arb_fpwrap.h"
 
-int main()
+int main(void)
 {
     double x, y;
     complex_double cx, cy;
diff --git a/examples/functions_benchmark.c b/examples/functions_benchmark.c
index 3143d40e63..5aca68c9b4 100644
--- a/examples/functions_benchmark.c
+++ b/examples/functions_benchmark.c
@@ -92,7 +92,7 @@ slong limit[] = {
     1e7,
 };
 
-int main()
+int main(void)
 {
     arb_t x, y, res;
     slong n, prec;
diff --git a/examples/huge_expr.c b/examples/huge_expr.c
index a732178299..8c2f99497d 100644
--- a/examples/huge_expr.c
+++ b/examples/huge_expr.c
@@ -5,8 +5,6 @@
 #include "ca.h"
 #include "gr.h"
 
-#pragma GCC optimize("O1")
-
 int gr_sqrt_ui(gr_ptr x, ulong y, gr_ctx_t ctx)
 {
     int status = gr_set_ui(x, y, ctx);
diff --git a/examples/zeta_zeros.c b/examples/zeta_zeros.c
index ebdfa6dd44..0968eb243e 100644
--- a/examples/zeta_zeros.c
+++ b/examples/zeta_zeros.c
@@ -21,7 +21,7 @@ void print_zeros(arb_srcptr p, const fmpz_t n, slong len, slong digits)
     fmpz_clear(k);
 }
 
-void print_help()
+void print_help(void)
 {
     flint_printf("zeta_zeros [-n n] [-count n] [-prec n] [-digits n] [-threads n] "
                  "[-platt] [-noplatt] [-v] [-verbose] [-h] [-help]\n\n");