c - 将文件写入磁盘并使用缓冲区时 C 中的段错误 11

Question

此程序旨在创建一个输出正弦波文件，其中包含用户输入的持续时间、振幅、采样率和频率，用值填充缓冲区并在用数据写入新的 .aiff 文件之前应用短启动和衰减斜坡.

虽然我的程序编译得很好，但它在使用参数运行时遇到了“段错误 11”，在快速谷歌搜索后似乎与内存不足有关。我已经多次检查我的代码(主要是处理缓冲区大小和指向它的指针的区域)。

   /* playsine.c */
/* Creates a sine wave audio file with input outfile - duration - amplitude - sampling 
    rate - frequency */
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <portsf.h>

int makeSine(float *buffer, double amplitude, long numFrames, double sineFreq,
             double samplingPeriod){
    long i;
    double time;
    double twoPi = 2 * M_PI;
    for(i = 0, time = 0; i < numFrames; i++){
        buffer[i] = amplitude * sin(twoPi * sineFreq * time);
        time += samplingPeriod;
        }
    return i;
    }



   long attack(float *buffer, long attackFrames){
    long i = 0;
    double factor = 0.0, increment = 1.0/attackFrames;
    while(factor <= 1.0 && i < attackFrames){
        buffer[i] = factor * buffer[i];
        factor += increment;
        ++i;
        }
    return i;
    }

long decay(float *endBuffer, long decayFrames){
    long i = 0;
    double factor = 1.0, decrement = 1.0/decayFrames;
    while(factor >= 0.0 && i < decayFrames){
        endBuffer[i] = decayFrames * endBuffer[i];
        factor -= decrement;
        ++i;
        }
    return i;
    }

enum {nameArg, outArg, durArg, ampArg, sampArg, freqArg, numArg};

int main(int argc, char* argv[]){

    if(argc < numArg){
        printf("Usage:\toutfile.aiff\tduration(s)\tamplitude(0-1)\tsampling rate\t\
        frequency(hz)\n");
        return 1;
        }
    if(psf_init()){
        printf("Error: Unable to open portsf library\n");
        return 1;
        }

    PSF_PROPS props;
    int outfile;
    long numFrames, samplingRate = atol(argv[sampArg]);
    double amps = atof(argv[ampArg]), samplingPeriod = 1.0/samplingRate;
    double sineFreq = atof(argv[freqArg]), attackFrames = 0.005 * samplingRate;
    double decayFrames = 0.01 * samplingRate;
    float *buffer, duration = atof(argv[durArg]);   
    numFrames = (long)duration * samplingRate;
    float *endBuffer = buffer + (numFrames - (long)decayFrames);

//Fill structure    
    props.srate = samplingRate;
    props.chans = 1;
    props.samptype = PSF_SAMP_16;
    props.format = PSF_AIFF;
    props.chformat = MC_MONO;


//Assign buffer
    buffer = (float*)malloc(numFrames * props.chans * sizeof(float));
    if(buffer == 0){
        printf("Error: unable to allocate buffer\n");
        return 1;
    }else{
//Fill buffer
        if(makeSine(buffer, amps, numFrames, sineFreq, samplingPeriod) != numFrames){
            printf("Error: unable to create sinewave\n");
            return 1;
            }
        attack(buffer, attackFrames);
        decay(endBuffer, decayFrames);
        }

//Create an outfile
    outfile = psf_sndCreate(argv[outArg], &props, 0, 0, PSF_CREATE_RDWR);
    if(outfile < 0){
        printf("Error: unable to create %s\n", argv[outArg]);
        return 1;
        }
//Write buffer to file          
    printf("Writing %s ...\n", argv[outArg]);
    if(psf_sndWriteFloatFrames(outfile, buffer, numFrames) != numFrames){
        printf("Warning: error writing %s\n", argv[outArg]);
        return 1;
        }
//Close file    
    if(psf_sndClose(outfile)){
        printf("Warning: error closing %s\n", argv[outArg]);
        return 1;
        }

    psf_finish();
    return 1;
}

Answer 1

我在 decay() 和 attack() 中看到的两个直接问题:

long attack (float *buffer, long attackFrames) {
    long i;
    ...
        buffer[i] = factor * buffer[i];  //Oops, i is never initialized

变量i 从未被初始化。这是未定义的行为，很可能导致崩溃。我假设你真的想做这样的事情:

long attack (float *buffer, long attackFrames) {
    long i = 0;
    double factor = 0.0, increment = 1.0/attackFrames;

    while(factor <= 1.0 && i < attackFrames) {
        buffer[i] = factor * buffer[i];
        factor += increment;
        ++i;
    }

    return i;
}

编辑:另一个问题是您使用endBuffer 引用未初始化的内存:

 float *buffer;              // Buffer not initialized
 float *endBuffer = buffer + (numFrames - (long)decayFrames);  // Oops!
 ...
 buffer = (float*)malloc(numFrames * props.chans * sizeof(float)); 
 //endBuffer still points to buffer's original address which is who-knows-where

您应该在使用malloc()分配buffer之后分配endBuffer。