OpenEuphoria

1. what am I missing?

• Posted by jacques_desch Jun 18, 2009
• 1121 views
• Last edited Jun 19, 2009

here C code from termbits.h

typedef unsigned char cc_t;
typedef unsigned int speed_t;
typedef unsigned int tcflag_t;

1. define NCCS 19 /* there should be a sharp character before define not 1. */
   
   struct termios2 {
   tcflag_t c_iflag; /* input mode flags */
   tcflag_t c_oflag; /* output mode flags */
   tcflag_t c_cflag; /* control mode flags */
   tcflag_t c_lflag; /* local mode flags */
   cc_t c_line; /* line discipline */
   cc_t c_cc[NCCS]; /* control characters */
   speed_t c_ispeed; /* input speed */
   speed_t c_ospeed; /* output speed */
   };
   
   from this I compute 44 bytes for termios2 struct:
   4*4 + 1 + 19 + 2*4 = 44
   But if I allocate 44 bytes my program crash.
   I must allocate 45 bytes for it to works. Where is the missing byte?
   
   Jacques

3. Re: what am I missing?

• Posted by mattlewis (admin) Jun 19, 2009
• 1134 views

typedef unsigned char	cc_t; 
typedef unsigned int	speed_t; 
typedef unsigned int	tcflag_t; 
 
#define NCCS 19 
 
struct termios2 { 
	tcflag_t c_iflag;		/* input mode flags */ 
	tcflag_t c_oflag;		/* output mode flags */ 
	tcflag_t c_cflag;		/* control mode flags */ 
	tcflag_t c_lflag;		/* local mode flags */ 
	cc_t c_line;			/* line discipline */ 
	cc_t c_cc[NCCS];		/* control characters */ 
	speed_t c_ispeed;		/* input speed */ 
	speed_t c_ospeed;		/* output speed */ 
}; 

Yes, it's very compiler dependent. I added the following to your struct definition:

#include <stdio.h> 
 
int main(){ 
	struct termios2 t; 
	printf("termios2: %d\n", sizeof( struct termios2 ) ); 
	printf("c_iflag:  %p\n", &t.c_iflag ); 
	printf("c_oflag:  %p\n", &t.c_oflag ); 
	printf("c_cflag:  %p\n", &t.c_cflag ); 
	printf("c_lflag:  %p\n", &t.c_lflag ); 
	printf("c_line:   %p\n", &t.c_line ); 
	printf("c_cc:     %p\n", &t.c_cc ); 
	printf("c_ispeed: %p\n", &t.c_ispeed ); 
	printf("c_ospeed: %p\n", &t.c_ospeed ); 
	return 0; 
} 

  termios2: 44 
  c_iflag:  0006fe68 
  c_oflag:  0006fe6c 
  c_cflag:  0006fe70 
  c_lflag:  0006fe74 
  c_line:   0006fe78 
  c_cc:     0006fe79 
  c_ispeed: 0006fe8c 
  c_ospeed: 0006fe90 

Matt

5. Re: what am I missing?

• Posted by jacques_desch Jun 19, 2009
• 1115 views

I'm not writing C code but euphoria binding to termios, so sizeof() is of no use to me. Anyway there is not padding as when I peek the struct all members are at expected position here the code:

function peek_termios(atom pTermios) 
  return peek4u({pTermios,4}) & peek(pTermios+16) &  
         {peek({pTermios+17,NCCS})} & peek4u({pTermios+17+NCCS,2}) 
end function 
 
 

the extra byte is at end of allocated struct. Matt code give this on Linpus lite compiled with gcc 4.1.2

termios2: 44 
c_iflag:  0xbfc9e408 
c_oflag:  0xbfc9e40c 
c_cflag:  0xbfc9e410 
c_lflag:  0xbfc9e414 
c_line:   0xbfc9e418 
c_cc:     0xbfc9e419 
c_ispeed: 0xbfc9e42c 
c_ospeed: 0xbfc9e430 

jacques

7. Re: what am I missing?

• Posted by jacques_desch Jun 19, 2009
• 1115 views

termios2: 44 
c_iflag:  0xbfc9e408 
c_oflag:  0xbfc9e40c 
c_cflag:  0xbfc9e410 
c_lflag:  0xbfc9e414 
c_line:   0xbfc9e418 
c_cc:     0xbfc9e419 
c_ispeed: 0xbfc9e42c 
c_ospeed: 0xbfc9e430 

Matt, Following you suggestion, here de C code I tested and it crash too, but only if I free t pointer. The same is true in my euphoria binding.

#include <stdio.h> 
#include <asm/termbits.h> 
#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <stdlib.h> 
 
int main(){ 
int fd, fnVal; 
struct termios2 *t; 
  fd = open("/dev/tty0",O_RDONLY); 
  printf("file handle %d\n", fd); 
  t = malloc(sizeof(struct termios2)); 
  fnVal = tcgetattr(fd, t); 
  printf("ispeed %d, ospeed %d\n",t->c_ispeed, t->c_ospeed); 
  free(t); // it doesn't crash if I don't free t. 
  puts("t freed\n"); 
  close(fd); 
} 
 
 

9. Re: what am I missing?

• Posted by jacques_desch Jun 19, 2009
• 1121 views

#include <stdio.h> 
#include <asm/termbits.h> 
#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <stdlib.h> 
 
int main(){ 
int fd, fnVal; 
struct termios2 *t; 
  fd = open("/dev/tty0",O_RDONLY); 
  printf("file handle %d\n", fd); 
  t = malloc(sizeof(struct termios2)); 
  fnVal = tcgetattr(fd, t); 
  printf("ispeed %d, ospeed %d\n",t->c_ispeed, t->c_ospeed); 
  free(t); // it doesn't crash if I don't free t. 
  puts("t freed\n"); 
  close(fd); 
} 
 
 

#include <stdio.h>  
#include <termios.h>  
#include <fcntl.h>  
  
int main(){  
int fd, fnVal;  
struct termios *t;  
	printf("termios %d\n", sizeof( struct termios ) ); 
  fd = open("/dev/tty",O_RDONLY);  
  printf("file handle %d\n", fd);  
  t = malloc(sizeof(struct termios));  
  fnVal = tcgetattr(fd, t);  
  printf("fnVal %d ispeed %d, ospeed %d\n", fnVal, t->c_ispeed, t->c_ospeed); 
  free(t); // it doesn't crash if I don't free t.  
  puts("t freed\n");  
  close(fd);  
}  

You got Matt, many Thanks.

11. Re: what am I missing?

• Posted by jacques_desch Jun 19, 2009
• 1115 views

I found the good definition of termios in <bits/termios.h> the only difference with termios2 is the NCCS which is 32 instead of 19 which give 57 bytes although sizeof() report 60, probably pad end of struct to align DWORD.

Jacques

13. Re: what am I missing?

• Posted by jimcbrown (admin) Jun 20, 2009
• 1059 views

Agreed. In general, I'd recommend writing a partical C wrapper in between the library and the part of the wrapper written in Euphoria, in the way Matt has a custom C library that wraps wxWidgets in C first before being wrapped in Eu, and the way Irv used to have a C library that wrapped parts of GTK (like the C macros which otherwise had to be ported by hand and then hardcoded in Eu) for euGTK.

In fact, I seem to recall that the C library wrapper for EuGTK specifically had functions that merely returned the value of a sizeof().