/*Hi folks. Heres a very odd trouble ( for me at least)
I was reading a book where it was stated that
" char *ptr = "text"; " is an allowed declaration and that
the compiler automatically allocates space for the string text and for the
\0 terminating character ( true) .
I decided to try it with strcpy(char *dest, const char *src) and
there seems to be a problem. Whenever dest is a pointer declared as above
theres a segmentation fault. I tried the code bellow which suffers from
exactly the same. The problem seems to relly In the expression
"while ( (*dest++ = *src++)!= '\0' )" .
I tried all the combinations with strcpy, but only this one gave odd results.
It seems that the compiler as some dificulties assigning *dest++ = *src++
when dest is a char *ptr = "kljdflg". But when src is this kind of
pointer and dest is an array ( as so declared) ,
it works fine. Its not very usual to declare strings this way
but its stated as ansi compliant, and the compiler silently accepts it
without any warnings.
The code is set to the particular combination where a SIGSEGV is generated
dest=s1; /*char *s1 = "ldksj"
src=string; /*char string[]= "dflkjg"*/
Can someone solve this mistery ?
#include <stdlib.h>
#include <stdio.h>
/*#include <string.h>*/
// this is strcpy source code borrowed from string.h with another name
char *strc(char *dest,const char *src)
{
char *tmp = dest;
while ( (*dest++ = *src++)!= '\0' );
return tmp;
}
int main ( void ) {
char *s1 = "frase_1";
char *s2 = "frase_2";
char string[] = "frase_3";
char *dest, *src;
int i;
//See if theres a terminating character int the string
for( i = 0; i != strlen(string)+2; i++)
printf( " s1[%x]=%d string[%x]=%d \n",
s1+i, *(s1+i), string+i, string[i] );
//show s1 and string address
printf( "s1 %x string %x", s1, string);
fflush(stdout);
//strcpy simulation
dest=s1;
src=string;
//check if assignment is valid
printf(" dest %x src %x ", dest, src );
fflush(stdout);
//start copy
while ( (*(dest++) = *(src++)) != '\0' ) {
// want to see the address progression of dest and src
printf( "\n dest[%x]= src[%x]= ", dest, src );
fflush( stdout );
}
// the result
printf( "\n ret dest address %x val %s \n", s1, s1 );
}
