编译后出现这个问题，请问怎么解决？
warning：variable "fid" was set example-2806xLaunchpadDemo.c example-2806xLaunchpad line 248 C/C++ problem
程序如下：
void main()
{
volatile int status = 0;
uint16_t i;
volatile FILE *fid;
// If running from flash copy RAM only functions to RAM
#ifdef _FLASH
memcpy(&RamfuncsRunStart, &RamfuncsLoadStart, (size_t)&RamfuncsLoadSize);
#endif
// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2806x_SysCtrl.c file.
InitSysCtrl();
// Step 2. Initalize GPIO:
// This example function is found in the F2806x_Gpio.c file and
// illustrates how to set the GPIO to its default state.
// InitGpio(); Skipped for this example
// For this example, only init the pins for the SCI-A port.
// This function is found in the F2806x_Sci.c file.
InitSciaGpio();
// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
DINT;
// Initialize PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the F2806x_PieCtrl.c file.
InitPieCtrl();
// Disable CPU interrupts and clear all CPU interrupt flags:
IER = 0x0000;
IFR = 0x0000;
// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example. This is useful for debug purposes.
// The shell ISR routines are found in F2806x_DefaultIsr.c.
// This function is found in F2806x_PieVect.c.
InitPieVectTable();
EALLOW;
PieVectTable.TINT0 = &cpu_timer0_isr;
EDIS;
