Expert: Narendra - 4/22/2005

Question
When trying to compile a C program including the code below, I keep getting this error and I don't know what to do to fix it.  Please explain if you can!

COMPILATION ATTEMPT:
tommy@city-it ~/cdevel
$ gcc -Wall -ansi -pedantic -mno-cygwin -I . -o myfirstlib myfirstlib.c

ERROR:
In file included from myfirstlib.c:3:
myfuncs.h: In function 'getstring':
myfuncs.h:98: warning: passing arg 2 of 'sprintf' makes pointer from integer without a cast

CODE SUMMARY:
<code>

/* will act as the buffer into which user's response will be stored */
char lineofinput[255];

/* grabs a string from the command prompt */
char getstring (char strquestion[255])
{
 /* reset to empty from previous calls */
 char lineofinput[255];

 if (strlen (strquestion))
   printf ("%s", strquestion);

 fgets (lineofinput, sizeof (lineofinput), stdin);

 /* while we get an empty response */
 while (strlen (lineofinput) == 1)
   {
     if (strlen (strquestion) == 1)
        printf ("Empty answers not permitted.  Please try again: ");

     return (sprintf("%s", getstring (lineofinput)));
   }

 return (sprintf("%s", lineofinput));
}

</code>

Complete code may be downloaded from my website at www.atrixnet.com/aequestion.tar.gz (It's only 1 Kb)

MY COMPILER:
tommy@city-it ~/cdevel
$ gcc -v
Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/3.3.3/specs
Configured with: /gcc/gcc-3.3.3-3/configure --verbose --prefix=/usr --exec-prefi
x=/usr --sysconfdir=/etc --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --enable-languages=c,ada,c++,d,f77,java,objc,
pascal --enable-nls --without-included-gettext --enable-libgcj --with-system-zlib --enable-interpreter --enable-threads=posix --enable-java-gc=boehm --enable-sjlj-exceptions --disable-version-specific-runtime-libs --disable-win32-registry
Thread model: posix
gcc version 3.3.3 (cygwin special)

Answer
For sprintf(), the first argument has to be a string variable.
For example:
char *str = (char *) malloc(100);
int i = 10;
float f = 5.34;
char mystr[] = "MY STRING";
sprintf(str, "%d %s %f", i, mystr, f);

In the above example, you can see that the first argument for sprintf() is a string variable str.
After sprintf() gets executed, the value will be stored in that.

Hope this helps.

-Narendra