Re: newlib port problem (stdio and malloc)

["MBT:Zhang Hua" <zhanghua at megabyte dot com dot cn>]

Hello Nick,

    I think I don't understand you completely.

   1.  Do you mean when we use -DREENTRANT_SYSCALLS_PROVIDED option, we can remove "\newlib\libc\sys\arm\syscalls.c" and then compile the newlib? 
    # I just try to remove it, and there is error when compile.
   
    2. If we can do step 1, then when we link the newlib, the non-static functions in "syscalls.c" are replaced by the functions in our applications?
    # That is, can I even use the resource in my own application to implement the non-static functions?

Thank you very much

Zhang Hua
    
----- Original Message ----- 
From: "Nick THOMPSON" <nickthompson@agere.com>
To: "MBT:Zhang Hua" <zhanghua@megabyte.com.cn>
Cc: <newlib@sources.redhat.com>
Sent: Wednesday, June 09, 2004 5:02 PM
Subject: Re: newlib port problem (stdio and malloc)


> Zhang Hua,
> 
> I have just done this for ARM also. The method I used was to leave
> syscalls.c alone and create a new file in my application code that
> replaces all the non-static functions in syscalls.c. So I started with
> stubs for all of:
> 
> int     _system     (const char *s);
> int     _rename     (const char *, const char *);
> int     isatty (int);
> clock_t _times (struct tms *);
> int     _gettimeofday (struct timeval *, struct timezone *);
> void    _raise (void);
> int     _unlink (void);
> int     _link (void);
> int     _stat (const char *, struct stat *);
> int     _fstat (int, struct stat *);
> caddr_t _sbrk (int);
> int     _getpid (int);
> int     _kill (int, int);
> void    _exit (int);
> int     _close (int);
> int     _open (const char *, int, ...);
> int     _write (int, char *, int);
> int     _lseek (int, int, int);
> int     _read (int, char *, int);
> 
> int _close_r (struct _reent *r, int file);
> _ssize_t _write_r   (struct _reent *r, int file, const void *ptr,
> size_t len);
> _off_t _lseek_r     (struct _reent *r, int file, _off_t off, int dir);
> _ssize_t _read_r    (struct _reent *r, int file, void *ptr, size_t
> len);
> int _fstat_r (struct _reent *r, int file, struct stat *fd);
> 
> e.g., one I don't use:
> 
> int     isatty (int fd)
> {
>     return 0;
> }
> 
> Then for write I have:
> 
> #define FH_OFFSET 20
> #define FH_CONSOLE 1
> remap_handle (int fh)
> {
>   if (fh == STDIN_FILENO)
>     return FH_CONSOLE;
>   if (fh == STDOUT_FILENO)
>     return FH_CONSOLE;
>   if (fh == STDERR_FILENO)
>     return FH_CONSOLE;
> 
>   return fh - FH_OFFSET;
> }
> 
> int     _write (int file, char *ptr, int len)
> {
>     // not called by newlib - but I use it
>     _sys_write(remap_handle(file), ptr, len);
>     return len;
> }
> 
> _ssize_t _write_r   (struct _reent *r, int file, const void *ptr, size_t
> len)
> {
>     _sys_write(remap_handle(file), ptr, len);
>     return len;
> }
> 
> extern int _sys_write(FILEHANDLE fh, const unsigned char *buf, unsigned
> len)
> {
>     if ((fh >= 0) && (fh <= 2)) { // possible range of FH_CONSOLE
>         while(len--) {
>             _OUTCHR(fh, *buf++);  // Write one char to UART
>         }
>         return(0); // remaining chars is ALWAYS zero
>     } else {
>         return(-1); // I don't support other devices yet
>     }
> }
> 
> When building newlib I had:
> 
> CFLAGS_FOR_TARGET = -O2 $(CFLAGS) -DMALLOC_PROVIDED \
> -DREENTRANT_SYSCALLS_PROVIDED
> 
> In the Makefile, so puts, printf, etc all end up calling my _write_r.
> 
> Since I have also defined _sbrk, I could define for myself exactly what
> memory it manages. In fact in my app, I have my own OS malloc routines
> (as you can see from my CFLAGS_FOR_TARGET), so I haven't bothered with
> _sbrk.
> 
> Since I have defined new versions of all non-statics in syscalls.c, the
> newlib file is left out of the final link. This allows me to build a
> stock newlib, with no changes (except for the tweak in Makefile).
> 
> Hope that helps.
> Nick.
> 
> On Wed, 2004-06-09 at 02:44, MBT:Zhang Hua wrote:
> > Hello everyone:
> > 
> >     I have 2 questions when port the newlib to the ARM platform:
> > 
> > 1. I need use stdio to display debug information. The debug information is output by the UART.
> >     Now I modify the function "int _swiwrite ( int    file,    char * ptr,    int    len)" in "\newlib-1.10.0\newlib\libc\sys\arm\syscalls.c".
> >     This function is modified something like this:
> >     for (i=0; i<len; i++)
> >     {
> >         while(1)
> >         {
> >             if (UART can send data)
> >             {
> >                 break;
> >             }    
> >         }
> >         send one byte
> >     }
> > 
> >     Is it OK?
> >     When I use stdio function, I find it's not a good way to modify like this.
> >     Any suggestion?
> > 
> > 2. I need use malloc/free to manage memory. When I check the function "caddr_t _sbrk (int incr)" in "\newlib-1.10.0\newlib\libc\sys\arm\syscalls.c", I find _sbrk() tries to manage the memory between [end, sp). 
> >     Although it's ok to manage like this, I want to know why  _sbrk() on the ARM system doesn't try to manage a fixed range of memory? For example, manage the memory between [end, end + MEMORY_SIZE). 
> > 
> > Thanks in advance
> > 
> > Zhang Hua
> 
>