Problem Compiling C code on FC4

BBPS · 09-30-2005, 04:43 AM

Hi,

I am not a C programmer at all, but have been given the task of compiling some custom C programs on Fedora Core 4.

When compiling some C code that compiles fine on another machine, I was getting some errors, so I tried the most basic of code to compile and this too had errors.

This is the simple code I tried to compile:

Quote:

#include <stdlib.h>

static void cleanup(void) __attribute__ ((destructor));

main()
{
printf("\nHello World\n");
exit(0);
}

void cleanup(void)
{
printf("\nCleaning up using destructors\n\n");
}

When I compile it using the command:

gcc test.c -o test.exe

...I get the following warnings:

Quote:

test.c: In function 'main':
test.c:7: warning: incompatible implicit declaration of built-in function 'printf'
test.c: In function 'cleanup':
test.c:13: warning: incompatible implicit declaration of built-in function 'printf'

It does compile, and creates the test.exe which works as I would expect:

Quote:

# ./test.exe

Hello World

Cleaning up using destructors

I am running Kernel 2.6.12

Quote:

Linux svr-fc4 2.6.12-1.1456_FC4smp #1 SMP Thu Sep 22 02:22:14 EDT 2005 i686 i686 i386 GNU/Linux

I have version 4.0.1 of GCC Installed:

Quote:

#gcc -v
Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,java,f95,ada --enable-java-awt=gtk --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --host=i386-redhat-linux
Thread model: posix
gcc version 4.0.1 20050727 (Red Hat 4.0.1-5)

Does anyone know how I can get it to compile without the warnings please ?

Many thanks,

Paul.

Mega Man X · 09-30-2005, 06:01 AM

Hi!

You are passing wrong arguments to the GNU compiler. .exe are also Windows executables. Try:

gcc -o test test.c

That will compile test.c into an executable file called test. You should be able to execute that file by typing ./test on the same folder where the source code is.

Regards!

BBPS · 09-30-2005, 06:07 AM

Hi Mega Man,

Many thanks for taking the time to reply. I did try before with different extensions for the output file, but had the same results.

I tried doing it how you suggested, but still get the same warnings:

Quote:

# gcc -o test test.c
test.c: In function 'main':
test.c:7: warning: incompatible implicit declaration of built-in function 'printf'
test.c: In function 'cleanup':
test.c:13: warning: incompatible implicit declaration of built-in function 'printf'
# ./test

Hello World

Cleaning up using destructors

#

...any other suggestions ?

Thanks,

Paul.

Wim Sturkenboom · 09-30-2005, 07:51 AM

You must include stdio.h; that contains the prototype for printf.

Be carefull with the use of the name test for your resulting program as it's a standard Linux command.

BBPS · 09-30-2005, 11:23 AM

Hi Wim, many thanks for that, I managed to compile that fine....and even managed to work out why the main program I was compiling didn't work.

Cheers,

Paul.