outline details from C18 annex F

1 files changed, 18 insertions, 0 deletions

diff --git a/src/math/tgamma.c b/src/math/tgamma.c
index b80584ac..63e25a5b 100644
--- a/src/math/tgamma.c
+++ b/src/math/tgamma.c
@@ -1,9 +1,27 @@
 # define TGSOURCE "tgamma.c"
 #include "_tgmath.h"
 #include <math.h>
+#include "fenv.h"
 
 TYPE TGFN(tgamma)(TYPE x)
 {
+	switch (fpclassify(x)) {
+	case FP_ZERO:
+		feraiseexcept(FE_DIVBYZERO);
+		return signbit(x) ? - INFINITY : INFINITY;
+
+	case FP_INFINITE:
+		if (signbit(x)) {
+			feraiseexcept(FE_INVALID);
+			return NAN;
+		} else {
+			return INFINITY;
+		}
+
+	default:
+		break;
+	}
+
 	return x;
 }