diff --git a/test/crt-test.c b/test/crt-test.c
index 5f19fb2..aadbf25 100644
--- a/test/crt-test.c
+++ b/test/crt-test.c
@@ -16,7 +16,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-#ifdef __linux__
+#if defined(__linux__) && !defined(_GNU_SOURCE)
 #define _GNU_SOURCE
 #endif
 #include <stdio.h>
@@ -370,7 +370,7 @@ void test_strings() {
     }
 #endif /* !MSVCRT_DLL_NOANSI */
 #endif /* long double tests */
-    snprintf(buf, sizeof(buf), "%"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64" %"PRIx64, myconst + 0, myconst + 1, myconst + 2, myconst + 3, myconst + 4, myconst + 5, myconst + 6, myconst + 7, myconst + 8, myconst + 9);
+    snprintf(buf, sizeof(buf), "%" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64" %" PRIx64, myconst + 0, myconst + 1, myconst + 2, myconst + 3, myconst + 4, myconst + 5, myconst + 6, myconst + 7, myconst + 8, myconst + 9);
     TEST_STR(buf, "baadf00dcafe baadf00dcaff baadf00dcb00 baadf00dcb01 baadf00dcb02 baadf00dcb03 baadf00dcb04 baadf00dcb05 baadf00dcb06 baadf00dcb07");
     char fmt[10] = { '%', '+', '0', '5', 'd', '\0' };
     snprintf(buf, sizeof(buf), fmt, 42);
@@ -386,7 +386,7 @@ void test_strings() {
     TEST_STR(buf, "0002a");
 
     uint64_t val0, val1, val2, val3, val4, val5, val6, val7, val8, val9;
-    if (sscanf("baadf00dcafe baadf00dcaff baadf00dcb00 baadf00dcb01 baadf00dcb02 baadf00dcb03 baadf00dcb04 baadf00dcb05 baadf00dcb06 baadf00dcb07", "%"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64, &val0, &val1, &val2, &val3, &val4, &val5, &val6, &val7, &val8, &val9) != 10) {
+    if (sscanf("baadf00dcafe baadf00dcaff baadf00dcb00 baadf00dcb01 baadf00dcb02 baadf00dcb03 baadf00dcb04 baadf00dcb05 baadf00dcb06 baadf00dcb07", "%" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64, &val0, &val1, &val2, &val3, &val4, &val5, &val6, &val7, &val8, &val9) != 10) {
         fails++;
         printf("sscanf failed\n");
     } else {
@@ -409,7 +409,7 @@ void test_strings() {
     tests++;
 
     val0 = val1 = val2 = val3 = val4 = val5 = val6 = val7 = val8 = val9 = 0xff;
-    if (vsscanf_wrap("baadf00dcafe baadf00dcaff baadf00dcb00 baadf00dcb01 baadf00dcb02 baadf00dcb03 baadf00dcb04 baadf00dcb05 baadf00dcb06 baadf00dcb07", "%"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64" %"SCNx64, &val0, &val1, &val2, &val3, &val4, &val5, &val6, &val7, &val8, &val9) != 10) {
+    if (vsscanf_wrap("baadf00dcafe baadf00dcaff baadf00dcb00 baadf00dcb01 baadf00dcb02 baadf00dcb03 baadf00dcb04 baadf00dcb05 baadf00dcb06 baadf00dcb07", "%" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64" %" SCNx64, &val0, &val1, &val2, &val3, &val4, &val5, &val6, &val7, &val8, &val9) != 10) {
         fails++;
         printf("vsscanf failed\n");
     } else {
@@ -549,7 +549,8 @@ void test_parse_numbers() {
 
 void test_environment() {
     int env_ok = 0;
-    putenv("CRT_TEST_VAR=1");
+    char buf1[] = "CRT_TEST_VAR=1";
+    putenv(buf1);
     for (char **ptr = environ; *ptr; ptr++)
         if (!strcmp(*ptr, "CRT_TEST_VAR=1"))
             env_ok = 1;
@@ -559,7 +560,8 @@ void test_environment() {
     }
     tests++;
     env_ok = 0;
-    putenv("CRT_TEST_VAR=2");
+    char buf2[] = "CRT_TEST_VAR=2";
+    putenv(buf2);
     for (char **ptr = environ; *ptr; ptr++)
         if (!strcmp(*ptr, "CRT_TEST_VAR=2"))
             env_ok = 1;
@@ -1992,10 +1994,10 @@ void test_win32_intrinsics() {
     TEST_FUNC(InterlockedExchange(&value, 2), value, 2, 6);
     TEST_FUNC(InterlockedCompareExchange(&value, 7, 1), value, 2, 2);
     TEST_FUNC(InterlockedCompareExchange(&value, 5, 2), value, 5, 2);
-    TEST_FUNC_PTR(InterlockedExchangePointer(&ptr, ptr1), ptr, ptr1, NULL);
+    TEST_FUNC_PTR(InterlockedExchangePointer(&ptr, ptr1), ptr, ptr1, (void*)NULL);
     TEST_FUNC_PTR(InterlockedExchangePointer(&ptr, ptr2), ptr, ptr2, ptr1);
     TEST_FUNC_PTR(InterlockedCompareExchangePointer(&ptr, NULL, ptr1), ptr, ptr2, ptr2);
-    TEST_FUNC_PTR(InterlockedCompareExchangePointer(&ptr, NULL, ptr2), ptr, NULL, ptr2);
+    TEST_FUNC_PTR(InterlockedCompareExchangePointer(&ptr, NULL, ptr2), ptr, (void*)NULL, ptr2);
     TEST_FUNC(InterlockedExchangeAdd64(&value64, 0x10000000000), value64, 0x10000000005, 5);
     TEST_FUNC(InterlockedExchange64(&value64, 0x10000000000), value64, 0x10000000000, 0x10000000005);
     TEST_FUNC(InterlockedCompareExchange64(&value64, 7, 1), value64, 0x10000000000, 0x10000000000);
@@ -2098,10 +2100,10 @@ void test_win32_intrinsics() {
     TEST_FUNC(_InterlockedExchange(&value, 2), value, 2, 1);
     TEST_FUNC(_InterlockedCompareExchange(&value, 7, 1), value, 2, 2);
     TEST_FUNC(_InterlockedCompareExchange(&value, 0, 2), value, 0, 2);
-    TEST_FUNC_PTR(_InterlockedExchangePointer(&ptr, ptr1), ptr, ptr1, NULL);
+    TEST_FUNC_PTR(_InterlockedExchangePointer(&ptr, ptr1), ptr, ptr1, (void*)NULL);
     TEST_FUNC_PTR(_InterlockedExchangePointer(&ptr, ptr2), ptr, ptr2, ptr1);
     TEST_FUNC_PTR(_InterlockedCompareExchangePointer(&ptr, NULL, ptr1), ptr, ptr2, ptr2);
-    TEST_FUNC_PTR(_InterlockedCompareExchangePointer(&ptr, NULL, ptr2), ptr, NULL, ptr2);
+    TEST_FUNC_PTR(_InterlockedCompareExchangePointer(&ptr, NULL, ptr2), ptr, (void*)NULL, ptr2);
 #ifdef _WIN64
     TEST_FUNC(_InterlockedExchangeAdd64(&value64, 0x20000000000), value64, 0x20000000000, 0);
     TEST_FUNC(_InterlockedExchange64(&value64, 0x10000000000), value64, 0x10000000000, 0x20000000000);