Permission denied executing any gcc-compiled c program on OS X (10.8.2) Mountain Lion

Question

When executing any C program that I have compiled with gcc from the terminal, I get a permission denied error.

To start, I have verified and repaired permissions on my drive (before doing this, the same problem was happening).

To illustrate and isolate the problem, I'll show you what happens with this ultra-simple Hello World program (with other programs, the same thing occurs):

#include <stdio.h>

main()
{
    printf("Hello World");
}

Now, I save this to my desktop as helloworld.c. At this point, from the desktop, an ls -l returns:

total 8
-rw-r--r--  1 michael  staff  56 Mar 13 14:08 helloworld.c

I then compile with gcc -c helloworld.c -o helloworld (I've also tried compiling without the -o flag with the same results). No warnings or errors. An ls -l now returns:

total 16
-rw-r--r--  1 michael  staff   56 Mar 13 14:08 helloworld.c
-rw-r--r--  1 michael  staff  724 Mar 13 14:16 helloworld.o

Attempting to execute the output of gcc, with ./helloworld.o returns:

-bash: ./helloworld.o: Permission denied

Just for the sake of debugging, if I execute with sudo (sudo ./helloworld.o), it returns:

sudo: ./helloworld.o: command not found

Now, if I attempt to set the executable flag using chmod +x helloworld.o, as was recommended on a lot of search results I've found, ls -l returns:

total 16
-rw-r--r--  1 michael  staff   56 Mar 13 14:08 helloworld.c
-rwxr-xr-x  1 michael  staff  724 Mar 13 14:16 helloworld.o

However, attempting to execute with ./helloworld.o now returns:

-bash: ./helloworld.o: Malformed Mach-o file

Now, for debugging sake, where gcc returns:

/usr/bin/gcc

So, you can see that I am not using a third party gcc.

Does anyone know what could be the problem? I've tried searching around, but I couldn't find any working solutions. I was having this same problem earlier and have since freshly reinstalled OS X (for different reasons) and am still having this problem with a clean and organized development environment. For reference, I'm on OS X 10.8.2 and have Xcode 4.6 along with the latest version of Xcode Command Line tools (from Apple's developer website). I have not installed gcc from Homebrew or from any other third party source; it is the gcc that came with Xcode Command Line tools.

Thank you very much for your help! I really appreciate you taking your time to read, diagnose and offer your help. :)

Answer 1

You're trying to execute object code (helloworld.o) rather than compile and link an executable binary. Don't use the -c option. Run this instead:

$ gcc helloworld.c -o helloworld

It will be created with executable permissions. You can then run.

$ ./helloworld

as normal.

---

The reason for this is that the -c option tells the compiler just to compile the file, but not link it. The link process is needed to create the final executable file. If you don't supply -c, gcc will both compile and link for you behind the scenes.