OP_DIV_*: add division by zero checks.

Now all the OP_DIV operations emit a warning and proceed on division by
zero, instead of potentially crashing the program.

This also handles the special case of -2147483648 / -1, which also traps on
x86 and thus must be handled.

prvm_execprogram.h

@@ -884,21 +884,59 @@ prvm_eval_t *src;
 				OPC->vector[2] = (prvm_vec_t) OPB->_int * OPA->vector[2];
 				DISPATCH_OPCODE();
 			HANDLE_OPCODE(OP_DIV_VF):
+				if( OPB->_float != 0.0f )
 				{
 					float temp = 1.0f / OPB->_float;
 					OPC->vector[0] = temp * OPA->vector[0];
 					OPC->vector[1] = temp * OPA->vector[1];
 					OPC->vector[2] = temp * OPA->vector[2];
 				}
+				else
+				{
+					PRE_ERROR();
+					VM_Warning(prog, "Attempted division of '%f %f %f' by zero\n", OPA->vector[0], OPA->vector[1], OPA->vector[2]);
+					OPC->vector[0] = 0.0f;
+					OPC->vector[1] = 0.0f;
+					OPC->vector[2] = 0.0f;
+				}
 				DISPATCH_OPCODE();
 			HANDLE_OPCODE(OP_DIV_I):
-				OPC->_int = OPA->_int / OPB->_int;
+				// NOTE: This also catches the second kind of division that can trap, namely, -2147483648 / -1,
+				// whose result is not representable as int32_t and raises the same CPU exception.
+				if( OPB->_int != 0 && (OPB->_int != -1 || OPA->_int != PRVM_INT_MIN) )
+				{
+					OPC->_int = OPA->_int / OPB->_int;
+				}
+				else
+				{
+					PRE_ERROR();
+					VM_Warning(prog, "Attempted division of %d by %d\n", (int)OPA->_int, (int)OPB->_int);
+					OPC->_int = 0;
+				}
 				DISPATCH_OPCODE();
 			HANDLE_OPCODE(OP_DIV_IF):
-				OPC->_float = ((prvm_vec_t) OPA->_int) / OPB->_float;
+				if( OPB->_float != 0.0f )
+				{
+					OPC->_float = ((prvm_vec_t) OPA->_int) / OPB->_float;
+				}
+				else
+				{
+					PRE_ERROR();
+					VM_Warning(prog, "Attempted division of %d by zero\n", (int)OPA->_int);
+					OPC->_float = 0;
+				}
 				DISPATCH_OPCODE();
 			HANDLE_OPCODE(OP_DIV_FI):
-				OPC->_float = OPA->_float / (prvm_vec_t) OPB->_int;
+				if( OPB->_int != 0 )
+				{
+					OPC->_float = OPA->_float / (prvm_vec_t) OPB->_int;
+				}
+				else
+				{
+					PRE_ERROR();
+					VM_Warning(prog, "Attempted division of %f by zero\n", OPA->_float);
+					OPC->_float = 0;
+				}
 				DISPATCH_OPCODE();
 			HANDLE_OPCODE(OP_CONV_ITOF):
 				OPC->_float = OPA->_int;

qtypes.h

@@ -49,12 +49,16 @@ typedef int64_t prvm_int_t;
 typedef uint64_t prvm_uint_t;
 #define PRVM_PRIi PRIi64
 #define PRVM_PRIu PRIu64
+#define PRVM_INT_MIN INT64_MIN
+#define PRVM_INT_MAX INT64_MAX
 #else
 typedef float prvm_vec_t;
 typedef int32_t prvm_int_t;
 typedef uint32_t prvm_uint_t;
 #define PRVM_PRIi PRIi32
 #define PRVM_PRIu PRIu32
+#define PRVM_INT_MIN INT32_MIN
+#define PRVM_INT_MAX INT32_MAX
 #endif
 typedef prvm_vec_t prvm_vec3_t[3];