Add fallback method for non-GNUC compilers on add_int64 and sub_int64 functions.

1 files changed, 14 insertions, 0 deletions

diff --git a/main.c b/main.c
index 69c0e78..d1a66fc 100644
--- a/main.c
+++ b/main.c
@@ -221,19 +221,33 @@ char *sprint_time5_utf8(char *string, intmax_t time, int space) {
 
 int64_t add_int64(int64_t x, int64_t y) {
 	int64_t result;
+#ifdef __GNUC__
 	bool overflow = __builtin_add_overflow(x, y, &result);
 	if (overflow) {
 		result = ((uint64_t)x >> 63) + INT64_MAX; // Equivalent to (x > 0 ? INT64_MAX : INT64_MIN)
 	}
+#else
+	result =
+		(y > 0 && x > INT64_MAX - y) ? INT64_MAX :
+		(y < 0 && x < INT64_MIN - y) ? INT64_MIN :
+		x + y;
+#endif
 	return result;
 }
 
 int64_t sub_int64(int64_t x, int64_t y) {
 	int64_t result;
+#ifdef __GNUC__
 	bool overflow = __builtin_sub_overflow(x, y, &result);
 	if (overflow) {
 		result = ((uint64_t)x >> 63) + INT64_MAX; // Equivalent to (x > 0 ? INT64_MAX : INT64_MIN)
 	}
+#else
+	result =
+		(y < 0 && x > INT64_MAX + y) ? INT64_MAX :
+		(y > 0 && x < INT64_MIN + y) ? INT64_MIN :
+		x - y;
+#endif
 	return result;
 }