Can not call "gcc" from inside a Java program

Question

I am trying to call the GNU C compiler from a Java program to compile c++ file, but I get an error:

Here is the program

class HelloWorld { 
public static void main(String[] args)  { 
Runtime sys = Runtime.getRuntime();
System.out.println("Hello World!"); 
 try {
     String com = "g++ NB.cpp -o NNN";
     System.out.println(com);
     Process p = sys.exec(com);
 }
 catch (Exception ep) {
     System.err.println(ep);}
} 
 }

Here is what I get when I compiler and run the program

$javac HelloWorld.java
$java HelloWorld
Hello World!
gcc NB.cpp -o NB
java.io.IOException: Cannot run program "g++": CreateProcess error=5, Access is denied

Here is where the gcc is resides

$ which gcc
/usr/bin/gcc

And here if the contents of the PATH

$ echo $PATH
/usr/local/bin:/usr/bin:/cygdrive/c/Program Files/Java/jdk1.6.0_26/bin:/cygdrive/c/Program Files (x86)/MiKTeX 2.9/miktex/bin:/cygdrive/c/Windows/system32:/cygdrive/c/Windows:/cygdrive/c/Windo
ws/System32/Wbem:/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0:/cygdrive/d/SourceForge/vectorpascalcom: D:/Cygwin/bin:/cygdrive/d/make382:/cygdrive/d/usr/bin:/cygdrive/d/Program Files/TortoiseSV
N/bin:/cygdrive/d/SourceForge/vectorpascalcom:/usr/bin:/cygdrive/c/Program Files/Java/jdk1.6.0_26/bin

Can any one help?

It is most likely a permissions issue. The idea should work, but most likely your JVM doesn't have the right to invoke g++. Try running another executable and watching the output. — Daniel B. Chapman
– Daniel B. Chapman, Commented Aug 20, 2011 at 14:49
I tried running another executable file, which already display some results, through the same program, but I did not run at all. — You
– You, Commented Aug 20, 2011 at 16:20
@You: Have a look at my deleted answer. A moderator thought it doesn't answer the question, well maybe it doesn't, but surely it does more than the other two answers. In short: this is no Java problem, make g++ run from the command prompt and it'll run from Java too. — maaartinus
– maaartinus, Commented Aug 21, 2011 at 2:12

ak2 · Accepted Answer · 2011-08-27 19:25:47Z

4

+50

g++ in Cygwin usually is a symlink to either g++-3 or g++-4, but Cygwin symlinks aren't transparent to non-Cygwin programs. Therefore you need to invoke the symlink target directly.

answered Aug 27, 2011 at 19:25

ak2

6,82835 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

maaartinus Over a year ago

That's it - at least on my computer. Here the target is /etc/alternatives/g++, without any extension, so it probably can't be executed on Windoze anyway. Making a copy called g++.exe brought me further (to another problem which is probably specific to XP 64).

ak2 Over a year ago

Ah yes, I forgot about that; /etc/alternatives/g++ is another symlink. Making a copy does work of course, but the drawback is that things might get inconsistent when there's an update.

maaartinus Over a year ago

You're right, making a copy is wrong. The symlink leads to /usr/bin/g++-4.exe, but I can see no Windows directory corresponding to/usr/bin. Finally I've found C:\Programs\cygwin\bin\g++-4.exe, which complains when no input files are given, but otherwise does nothing at all. Strange.

Jon7 · Accepted Answer · 2011-08-20 15:02:01Z

1

Make sure you're running the java application through cygwin and not just a normal windows command shell. Also, try running the command on your own to make sure it's working.

And finally, this might not be applicable to your issue, but you should read the famous article when Runtime.exec() won't anyway.

answered Aug 20, 2011 at 15:02

Jon7

7,2352 gold badges35 silver badges39 bronze badges

3 Comments

You Over a year ago

Well, I am running it through Cygwin. The commend “gcc NP.cpp –o NN” on its own from Cygwin works fine, but not from a Java program.

Jon7 Over a year ago

Have you tried the command that your program is running? G++ not gcc.

You Over a year ago

Yes, but I get the same problem

Charles Goodwin · Accepted Answer · 2011-08-20 15:02:00Z

0

Try wrapping it with this:

java.security.AccessController.doPriveleged(new java.security.PrivilegedAction() {
    public Object Run() {
        Runtime sys = Runtime.getRuntime();
        System.out.println("Hello World!"); 
        try {
            String com = "g++ NB.cpp -o NNN";
            System.out.println(com);
            Process p = sys.exec(com);
        }
        catch (Exception ep) {
            System.err.println(ep);}
        } 
    }
}

answered Aug 20, 2011 at 15:02

Charles Goodwin

6,6923 gold badges37 silver badges64 bronze badges

1 Comment

maaartinus Over a year ago

This won't help, since the problem is running cygwin program from Windows.

Dominik · Accepted Answer · 2017-11-28 22:11:19Z

0

I don't think javac and java are Cygwin executables (i.e., they don't use cygwin1.dll), so they're not going to recognize Cygwin-specific file paths. You can execute them from a Cygwin shell, but you can do the same with any other non-Cygwin Windows executable. As far as your Java process is concerned, g++ isn't /usr/bin/g++, because there is no /usr/bin directory. (/usr/bin is actually a Cygwin mount point; the corresponding Windows directory is C:\cygwin\bin.)

Try this:

 String com = "C:\\cygwin\\bin\\sh -c 'g++ NB.cpp -o NNN'";
 System.out.println(com);
 Process p = sys.exec(com);

edited Nov 28, 2017 at 22:11

Dominik

1,1188 silver badges21 bronze badges

answered Aug 27, 2011 at 19:56

Keith Thompson

266k46 gold badges447 silver badges668 bronze badges

Collectives™ on Stack Overflow

Can not call "gcc" from inside a Java program

4 Answers 4

3 Comments

3 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

3 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related