我正在用C语言编写TI MSP430 ...我在调试器中遇到一个奇怪的问题，它显示if语句满足前进的条件，但在运行时没有这样做。有任何想法吗？函数中未评估的if语句位于星号之间。
void gps_parse(void){
gps_write();
lcd_out(" ", LCD_LINE_1);
lcd_out(" ", LCD_LINE_2);
lcd_out(GPSlat, LCD_LINE_1);
lcd_out(GPSlong, LCD_LINE_2);
SW2Press = NOT_PRESSED;
while(!SW2Press){
if (GPS_rx_ring_rd != GPS_rx_ring_wr) {
**if (GPS_Char_Rx[GPS_rx_ring_rd] == '$')**{
if (++GPS_rx_ring_rd >= (64)) {
GPS_rx_ring_rd = BEGINNING;
}
char GPS_data[64];
for (int i = 0; i < 64; i++) {
while(GPS_rx_ring_rd == GPS_rx_ring_wr);
GPS_data[i] = GPS_Char_Rx[GPS_rx_ring_rd];
if (++GPS_rx_ring_rd >= (64)) {
GPS_rx_ring_rd = 0; // Circular buffer back to beginning
}
}
if(GPS_data[0] == 'G' && GPS_data[1] == 'P' && GPS_data[2] == 'R' && GPS_data[3] == 'M' && GPS_data[4] == 'C'){
if(GPS_data[17] == 'A'){
//Fill in lats
GPSlat[4] = GPS_data[19];
GPSlat[5] = GPS_data[20];
GPSlat[6] = GPS_data[21];
GPSlat[7] = GPS_data[22];
GPSlat[8] = GPS_data[23];
GPSlat[9] = GPS_data[24];
GPSlat[10] = GPS_data[25];
GPSlat[11] = GPS_data[26];
GPSlat[12] = GPS_data[27];
GPSlat[15] = GPS_data[29];
//Fill in longs
GPSlong[4] = GPS_data[31];
GPSlong[5] = GPS_data[32];
GPSlong[6] = GPS_data[33];
GPSlong[7] = GPS_data[34];
GPSlong[8] = GPS_data[35];
GPSlong[9] = GPS_data[36];
GPSlong[10] = GPS_data[37];
GPSlong[11] = GPS_data[38];
GPSlong[12] = GPS_data[39];
GPSlong[13] = GPS_data[40];
GPSlong[15] = GPS_data[42];
} else{
GPSlat[15] = '?';
GPSlong[15] = '?';
}
lcd_out(GPSlat, LCD_LINE_1);
lcd_out(GPSlong, LCD_LINE_2);
}
else {
if (++GPS_rx_ring_rd >= (64)) {
GPS_rx_ring_rd = 0;
}
}
}
}
}
}
答案 0 :(得分：1)
尝试禁用编译器优化。有时，由于优化的代码，代码路径在调试器中看起来很奇怪。
答案 1 :(得分：0)
// the following compiles, but has not been run.
// it corrects the obvious logic errors
// it corrects certain coding errors
// and corrects certain erroneous assumptions
// I added several data definitions so it would compile
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern int SW2Press;
extern int GPS_rx_ring_rd; // contains next char index to extract from circular buffer
extern int GPS_rx_ring_wr; // contains next char index to write to circular buffer
extern char *GPS_Char_Rx;
void gps_parse(void);
void gps_write(void);
void lcd_out( char*, int);
#define LCD_LINE_1 (1)
#define LCD_LINE_2 (2)
#define MASK64 (0x40)
#define NOT_PRESSED (0)
void gps_parse()
{
// GPS_rx_ring_rd is a counter into a circular buffer
// GPS_rx_ring_wr is a counter into a circular buffer
// ??perhaps as head/tail indexes??
// the variables GPS_Lat[] and GPS_Long[]
// are set/used locally, so probably should be local variables, on the stack
char GPSlat[17] = {'\0'};
char GPSlong[17] = {'\0'};
strcat(GPSlat, "lat ");
strcat(GPSlong, "Long");
// start GPS sending NMEA messages
gps_write();
// initialize the LCD display
lcd_out(" ", LCD_LINE_1);
lcd_out(" ", LCD_LINE_2);
lcd_out(GPSlat, LCD_LINE_1);
lcd_out(GPSlong, LCD_LINE_2);
SW2Press = NOT_PRESSED; // global variable
char GPS_data[64];
int i = 0;
while(!SW2Press)
{ // while waiting for button press
// following assumes that GPS_rx_ring_rd
// points to next char to consume
// and should be initialized to same value as GPS_rx_ring_wr
if ( GPS_rx_ring_rd != GPS_rx_ring_wr )
{ // then, next char(s) has been input
// code needs to increment/wrap GPS_rs_ring_rd
// even when current char is NOT a '$'
// note: always put literal on left so compiler can catch
// '=' rather than '=='
// only when current char is a '$'
// should following code be executed
if ( '$' == GPS_Char_Rx[GPS_rx_ring_rd] )
{ // then, current checked char is '$'
// I.E. start of a new GPS message
GPS_rx_ring_rd++; // step past '$'
GPS_rx_ring_rd = (GPS_rx_ring_rd>= MASK64)? GPS_rx_ring_rd : 0;
// clear old trash from extracted buffer
memset( GPS_data, 0x00, sizeof(GPS_data) );
// for next 64 bytes input, extract bytes from
// circular buffer to array
// the assumption that each GPS message actually 64 bytes long
// is not true
// far better to stop extracting when 'next' char
// to extract is '$'
for ( i = 0; i < sizeof(GPS_data); i++)
{
// wait for next available char from GPS??
while(GPS_rx_ring_rd == GPS_rx_ring_wr);
if( '$' == GPS_Char_Rx[GPS_rx_ring_rd])
{ // then, all of current GPS message is extracted
break;
}
// extract next GPS char from circular buffer
GPS_data[i] = GPS_Char_Rx[GPS_rx_ring_rd];
// make special case not special
// if at end of circular buffer, wrap to beginning.
GPS_rx_ring_rd++;
GPS_rx_ring_rd = (GPS_rx_ring_rd>= MASK64)? GPS_rx_ring_rd : 0;
} // end for
if( GPS_data[0] == 'G'
&& GPS_data[1] == 'P'
&& GPS_data[2] == 'R'
&& GPS_data[3] == 'M'
&& GPS_data[4] == 'C')
{ // then, GPS message type GPRMC - minimum recommended data
// for SIRF chip set
// $GPRMC,120557.916,A,5058.7456,N,00647.0515,E,0.00,82.33,220503,,*39
if(GPS_data[17] == 'A')
{ // then, full data set available
//Fill in latitude
GPSlat[4] = GPS_data[19]; //degree - range 0...90
GPSlat[5] = GPS_data[20]; //degree
GPSlat[6] = GPS_data[21]; //minute - range 0...59
GPSlat[7] = GPS_data[22]; //minute
GPSlat[8] = GPS_data[23]; //decimal point
GPSlat[9] = GPS_data[24]; //fraction of minute
GPSlat[10] = GPS_data[25]; //fraction of minute
GPSlat[11] = GPS_data[26]; //fraction of minute
GPSlat[12] = GPS_data[27]; //fraction of minute
GPSlat[15] = GPS_data[29]; // N or S or blank
//Fill in longitude
GPSlong[4] = GPS_data[31]; //degree - range 0...360
GPSlong[5] = GPS_data[32]; //degree
GPSlong[6] = GPS_data[33]; //degree
GPSlong[7] = GPS_data[34]; //minute - range 0...59
GPSlong[8] = GPS_data[35]; //minute
GPSlong[9] = GPS_data[36]; //decimal point
GPSlong[10] = GPS_data[37]; //fraction of minute
GPSlong[11] = GPS_data[38]; //fraction of minute
GPSlong[12] = GPS_data[39]; //fraction of minute
GPSlong[13] = GPS_data[40]; //fraction of minute
GPSlong[15] = GPS_data[42]; // E or W or blank
}
else
{ // full data set not available
GPSlat[15] = '?'; // use old data and N/S byte indicates old data
GPSlong[15] = '?'; // use old data and E/W byte indicates old data
}
// update the LCD display
lcd_out(GPSlat, LCD_LINE_1);
lcd_out(GPSlong, LCD_LINE_2);
}
else
{ // else not a $GPRMC message
; // do nothing
} // end if
}
else
{ // else, step to next char
; do nothing
} // end if
} // end if
// make special case to be not special
// if at end of circular buffer, wrap to beginning
GPS_rx_ring_rd++;
GPS_rx_ring_rd = (GPS_rx_ring_rd>= MASK64)? GPS_rx_ring_rd : 0;
} // end while
} // end gps_parse