Avoid add overflow in summation in AMR-WB decoder

codec look was doing a int32+= int16*int16 MAC which was overflowing
instead of saturating. Standard  3GPP #26.173 says it should saturate.

Bug: 112160454
Test: poc no longer crashes
Change-Id: I2979425be6b5b7b1dbe6790daf431fc86ab591c5

parent b98450a7

media/libstagefright/codecs/amrwb/src/pvamrwbdecoder_basic_op_cequivalent.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -467,7 +467,12 @@ extern "C"
		__inline int32 fxp_mac_16by16(int16 var1, int16 var2, int32 L_add)
		{

		L_add += (int32)var1 * var2;
		int32 l_orig = L_add;
		if (__builtin_add_overflow( (int32)var1 * var2, l_orig, &L_add)) {
		// needs saturation
		if (l_orig > 0) L_add = MAX_32;
		else L_add = MIN_32;
		}

		return L_add;
		}