Invalid conversion from void * to char *

[Lewis Mbuthia]

I tried to write a program to write a wav file.Could you please debug it for me?

 
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
 
#define SECONDS 10 /* produce 10 second(s) of noise */
#define PI 3.14159265358979
 
int put_little_short(char *t, unsigned int value)
{
    *(unsigned char *)(t++)=value&255;
    *(unsigned char *)(t)=(value/256)&255;
    return 2;
}
int put_little_long(char *t, unsigned int value)
{
    *(unsigned char *)(t++)=value&255;
    *(unsigned char *)(t++)=(value/256)&255;
    *(unsigned char *)(t++)=(value/(256*256))&255;
    *(unsigned char *)(t)=(value/(256*256*256))&255;
    return 4;
}
 
/* returns the number of bytes written. skips two bytes after each write */
int fill_data(char *start, int frequency, int seconds)
{
    int i, len=0;
    double value;
    for(i=0; i<seconds*44100; i++) 
    {
        value=32767.0 * sin(2.0*PI*((double)(i))*(double)(frequency)/44100.0);
        put_little_short(start,int(value));
        start += 4;
        len+=2;
    }
    return len;
}
 
int main()
{
    char *buffer=malloc(SECONDS*44100*4+1000);
    char *t=buffer;
    int len;
    int fd;
 
    *t++='R'; *t++='I'; *t++='F'; *t++='F';
    t+=4; /* total length will be put in later */
    *t++='W'; *t++='A'; *t++='V'; *t++='E';
 
    /* format chunk, 8 bytes header and 16 bytes payload */
    *t++='f'; *t++='m'; *t++='t'; *t++=' ';
    t+=put_little_long(t,16); /* I know the length  of the fmt_ chunk*/
    t+=put_little_short(t,1); /* chunk type is always one */
    t+=put_little_short(t,2); /* two channels */
    t+=put_little_long(t,44100); /* samples per second */
    t+=put_little_long(t,44100*2*2); /* bytes per second */
    t+=put_little_short(t,4); /* bytes pro sample (all channels) */
    t+=put_little_short(t,16); /* bits per sample */
 
    /* data chunk, 8 bytes header and XXX bytes payload */
    *t++='d'; *t++='a'; *t++='t'; *t++='a';
 
    len=fill_data(t+4,450,SECONDS); /* left channel, 450Hz sine */
    len+=fill_data(t+6,452,SECONDS); /* right channel, 452Hz sine */
    put_little_long(t,len);
    put_little_long(buffer+4,len+8+16+8);
    fd=open("test.wav", O_RDWR|O_CREAT, 0644);
    write(fd,buffer,len+8+16+8+8);
    close(fd);
    return 0;
}
 
 

The problem is in the first line of the main program which my Dev-Cpp compiler says is an invalid conversion from void to char.
P.S. If you have a quick fix (like in type casting the buffer or the malloc) please text message the statement to me .My number is. I need the code urgently.
You may also send to my email another source code to carry out the same task. My only interest is that i be able to specify the frequency of the output wav file as per my requirements in the source code.

[Banfa]

You are compiling this code as C++ although it looks like C code.

C will implicitly cast void* to char*, or indeed any other pointer type; C++ wont.

Either compile the code as C or cast the output of malloc to char*.

Oh and next time copy and paste the actual compiler errors because the error you are getting is not "invalid conversion from void to char" but rather "invalid conversion from void * to char *"

[donbock]

By the way, you should always confirm malloc succeeded before you dereference the returned pointer.