我试图在Linux中编译C代码以在我的Raspberry Pi上制作软盘音乐。我使用Scott Vincent的代码来控制GPIO引脚，但我无法编译它。我在终端中使用此命令：
gcc -o floppy_music floppy_music.c
以下是代码：
# --------------------------------------
# Written by Scott Vincent
# 16 Feb 2014
# --------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wiringPi.h>
// pin 11 = wiringPi Pin 0. Use this for motor direction.
const int dirPin = 0;
// pin 12 supports pwm mode but it turns out I didn't need pwm mode in the end!
// pin 12 = wiringPi Pin 1. Use this for stepper motor.
const int stepPin = 1;
// Define an octave with naturals and sharps (Zz = rest)
enum { Cn, Cs, Dn, Ds, En, Fn, Fs, Gn, Gs, An, As, Bn, Zz };
// Define another one with flats and remaining sharps
enum { Bs, Df, Dn2, Ef, En2, Es, Gf, Gn2, Af, An2, Bf, Bn2, Zz2 };
/**
* Frequencies in hundredths of Hz, e.g. middle A = 44000
* 4 Octaves with 12 notes per octave, i.e. C to B
*/
const int freq[4][12] = {
{ 13081,13859,14683,15556,16481,17461,18500,19600,20765,22000,23308,24694 },
{ 26163,27718,29366,31113,32963,34923,36999,39200,41530,44000,46616,49388 },
{ 52325,55437,58733,62225,65925,69846,73999,78399,83061,88000,93233,98777 },
{ 104650,110873,117466,124451,131851,139691,147998,156798,166122,176000,186466,197553 }
};
/**
* Frequency (in Hz) is converted to Floppy Delay using the formula:
* 314000 / frequency = floppy delay
* so middle A = 314000 / 440 = 714
*
* Lowest realistic note is delay = 1550
* Highest realistic note is delay = 210
*/
const int floppyConv = 31400000;
// Calculate all our floppy delays at the start
int floppyDelay[4][12];
// Song1 is the C major scale (note, octave, length)
const int song1_tempo = 120;
const int song1[][3] = {
{ Cn, 1, 1 },
{ Dn, 1, 1 },
{ En, 1, 1 },
{ Fn, 1, 1 },
{ Gn, 1, 1 },
{ An, 1, 1 },
{ Bn, 1, 1 },
{ Cn, 2, 1 },
{ -1, -1, -1 }
};
// Song2 is The Imperial March from Star Wars (note, octave, length)
const int song2_tempo = 104 * 8;
const int song2[][3] = {
{ Gn, 1, 8 }, // Bar 1
{ Gn, 1, 8 },
{ Gn, 1, 8 },
{ Ef, 1, 6 },
{ Bf, 1, 2 },
{ Gn, 1, 8 },
{ Ef, 1, 6 },
{ Bf, 1, 2 },
{ Gn, 1, 16 },
{ Dn, 2, 8 },
{ Dn, 2, 8 },
{ Dn, 2, 8 },
{ Ef, 2, 6 },
{ Bf, 1, 2 },
{ Gf, 1, 8 }, // Bar 4
{ Ef, 1, 6 },
{ Bf, 1, 2 },
{ Gn, 1, 16 },
{ Gn, 2, 8 },
{ Gn, 1, 6 },
{ Gn, 1, 2 },
{ Gn, 2, 8 },
{ Gf, 2, 6 },
{ Fn, 2, 2 },
{ En, 2, 2 },
{ Ds, 2, 2 },
{ En, 2, 4 },
{ Zz, 0, 4 },
{ Gs, 1, 4 },
{ Cs, 2, 8 },
{ Bs, 2, 6 },
{ Bn, 1, 2 },
{ Bf, 1, 2 }, // Bar 7
{ An, 1, 2 },
{ Bf, 1, 4 },
{ Zz, 0, 4 },
{ Ef, 1, 4 },
{ Gf, 1, 8 },
{ Ef, 1, 6 },
{ Gf, 1, 2 },
{ Bf, 1, 8 },
{ Gn, 1, 6 },
{ Bf, 1, 2 },
{ Dn, 2, 16 },
{ Gn, 2, 8 },
{ Gn, 1, 6 },
{ Gn, 1, 2 },
{ Gn, 2, 8 },
{ Gf, 2, 6 },
{ Fn, 2, 2 },
{ En, 2, 2 }, // Bar 10
{ Ds, 2, 2 },
{ En, 2, 4 },
{ Zz, 0, 4 },
{ Gs, 1, 4 },
{ Cs, 2, 8 },
{ Bs, 2, 6 },
{ Bn, 1, 2 },
{ Bf, 1, 2 },
{ An, 1, 2 },
{ Bf, 1, 4 },
{ Zz, 0, 4 },
{ Ef, 1, 4 },
{ Gf, 1, 8 },
{ Ef, 1, 6 },
{ Bf, 1, 2 },
{ Gn, 1, 8 },
{ Ef, 1, 6 },
{ Bf, 1, 2 },
{ Gn, 1, 16 },
{ -1, -1, -1 }
};
/**
*
*/
static void resetMotor()
{
// To reset head position move back 10 then forward 5
digitalWrite(dirPin, LOW);
for (int i=0; i < 10; i++){
digitalWrite(stepPin, HIGH);
digitalWrite(stepPin, LOW);
delay(1);
}
digitalWrite(dirPin, HIGH);
for (int i=0; i < 5; i++){
digitalWrite(stepPin, HIGH);
digitalWrite(stepPin, LOW);
delay(1);
}
delay(400);
}
/**
*
*/
static int init()
{
if (wiringPiSetup() == -1){
printf("Failed to initialize wiringPi\n");
return 1;
}
pinMode(stepPin, OUTPUT);
pinMode(dirPin, OUTPUT);
resetMotor();
for (int octave = 0; octave < 4; octave++){
for (int note = 0; note < 12; note++){
floppyDelay[octave][note] = floppyConv / freq[octave][note];
}
}
return 0;
}
/**
*
*/
static void playNote(int note, int octave, int length)
{
static int dir = 1;
int pause = floppyDelay[octave][note] * 10;
int endTime = millis() + length;
while (millis() < endTime){
digitalWrite(dirPin, dir);
if (dir == 0)
dir = 1;
else
dir = 0;
digitalWrite(stepPin, HIGH);
digitalWrite(stepPin, LOW);
delayMicroseconds(pause);
}
}
/**
*
*/
static void rest(int length)
{
int endTime = millis() + length;
while (millis() < endTime){
delay(5);
}
}
/**
* song[note_num][note, octave, length]
*/
static void playSong(const int song[][3], const int tempo)
{
// Convert tempo in BPM to millisecs
int noteLen = 60000 / tempo;
for (int i = 0; song[i][0] != -1; i++){
int length = song[i][2] * noteLen;
if (song[i][0] == Zz){
rest(length);
}
else {
playNote(song[i][0], song[i][1], (7 * length) / 8);
rest(length / 8);
}
}
}
/**
*
*/
int main()
{
if (init() != 0){
printf("init failed - Exiting\n");
return 1;
}
playSong(song2, song2_tempo);
return 0;
}
以下是我得到的错误：
floppy_music.c:1:3: error: invalid preprocessing directive #--
floppy_music.c:2:3: error: invalid preprocessing directive #Written
floppy_music.c:3:6: error: "Feb" is not a valid filename
floppy_music.c:4:3: error: invalid preprocessing directive #--
floppy_music.c: In function 'resetMotor':
floppy_music.c:159:4: error: 'for' loop initial declarations are only allowed in C99 mode
floppy_music.c:159:4: note: use option -std=99 or -std=gnu99 to compile your code
floppy_music.c:166:13: error: redefinition of 'i'
floppy_music.c:159:13: note: previous definition of 'i' was here
floppy_music.c:166:4: error: 'for' loop initial declarations are only allowed in C99 mode
floppy_music.c: In function 'init:
floppy_music.c:191:4: error: 'for' loop initial declarations are only allowed in C99 mode
floppy_music.c:192:7: error: 'for' loop initial declarations are only allowed in C99 mode
floppy_music.c: In function 'playSong':
floppy_music.c:244:4: error: 'for' loop initial declarations are only allowed in C99 mode
但有趣的是，这段代码对他有用，所以有人知道这个问题是什么吗？
答案 0 :(得分：6)
它适用于您的朋友，因为他的编译器的默认设置恰好忽略了无效的预处理程序指令而且没有失败，并且还接受所有其他代码（在C99中有效）。
就预处理内容而言：
# --------------------------------------
# Written by Scott Vincent
# 16 Feb 2014
# --------------------------------------
但这些都没有评论。这应该是（或者你最喜欢的/* ... */风格）：
/*
--------------------------------------
Written by Scott Vincent
16 Feb 2014
--------------------------------------
*/
或者使用C ++风格的注释（对C99也有效）：
// --------------------------------------
// Written by Scott Vincent
// 16 Feb 2014
// --------------------------------------
以#开头的行是预处理程序指令;用于在编译之前处理文件的预处理器的特殊命令（例如#if）。只有一组有效的命令。这些不是评论。
您可以添加编译器标志以使gcc接受此操作，但最好对注释使用正确的注释语法，并将#留给实际的预处理指令。
对于其他问题，您可以按照编译器的建议进行操作，并使用选项-std=99或-std=gnu99来编译代码＆＃34;。例如。在for循环（for (int n ...）中声明变量至少需要C99。