Why this C program is crashing? Post: 302517289

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Top Forums Programming Why this C program is crashing? Post 302517289 by alister on Tuesday 26th of April 2011 10:52:55 AM

04-26-2011

Registered User

Quote:

Originally Posted by Perderabo

Code:

char* p="abcde";
printf("%c", 3[p]);

should work fine. I believe that this is just a test of the fact that p[3] and 3[p] are supposed to behave the same way. He probably going to enter the obfuscated C contest or something like that. Smilie

Hehehe. I was thinking the same thing.

A bit more info for those interested in this "feature": Question 6.11

And ... it gets worse:

Code:

$ cat acomm.c
#include <stdio.h>

int
main(int argc, char **argv) {
	char *s = "char *s";
	char *a[1][2][3];
	a[0][1][2] = s;

	(void) printf("%s\n", a[0][1][2]);
	(void) printf("%s\n", 2[1[0[a]]]);
	(void) printf("%s\n", 2[0[a][1]]);
	(void) printf("%s\n", 1[a[0]][2]);
	/* etc */

	return 0;
}


$ cc -Wall -pedantic acomm.c 
$ ./a.out 
char *s
char *s
char *s
char *s
$ cc --version
i686-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5370)
Copyright (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Regards,
Alister

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fxprintf

XPRINTF(3)						   BSD Library Functions Manual 						XPRINTF(3)

NAME

     asxprintf, dxprintf, fxprintf, sxprintf, xprintf, vasxprintf, vdxprintf, vfxprintf, vsxprintf, vxprintf -- extensible printf

SYNOPSIS

     #include <printf.h>

     int
     asxprintf(char ** restrict ret, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, ...);

     int
     dxprintf(int fd, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, ...);

     int
     fxprintf(FILE * restrict stream, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, ...);

     int
     sxprintf(char * restrict str, size_t size, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, ...);

     int
     xprintf(printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, ...);

     #include <stdarg.h>

     int
     vasxprintf(char ** restrict ret, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, va_list ap);

     int
     vdxprintf(int fd, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, va_list ap);

     int
     vfxprintf(FILE * restrict stream, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, va_list ap);

     int
     vsxprintf(char * restrict str, size_t size, printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format,
	 va_list ap);

     int
     vxprintf(printf_domain_t restrict domain, locale_t restrict loc, const char * restrict format, va_list ap);

DESCRIPTION

     These extensible printf (see xprintf(5)) variants behave like their normal printf counterparts (see printf(3)) without 'x' in the name
     (except sxprintf() and vsxprintf() behave like snprintf() and vsnprintf(), respectively).

     The domain argument must be a pointer to a printf domain structure, as returned by one of the functions described in xprintf_domain(3).  The
     loc argument should be an extended locale (see xlocale(3)) or NULL, which means to use the current locale in effect (either the per-thread
     locale if set, or the global locale by default).

SEE ALSO

     printf(3), xlocale(3), xprintf_domain(3), xprintf(5)

Darwin								   Aug 19, 2012 							    Darwin