On Sun, 2004-09-05 at 15:24, Phil Mattison wrote:
> Here's something that doesn't seem to work on Linux 
> the way I would have expected:
>  
> I wrote a small utility program in C++ using Kdevelop. It is a 
> console-mode program that uses only the stdio.h run-time
> library. I want to run it via exec() from a PHP script on a
> shared hosting web server. It all works fine on my 
> development machine but not the shared host. Neither 
> my machine nor the shared host are running PHP in safe 
> mode. When I run the custom program on the shared host
> via their provided SSH shell login I get an error indicating that
> the stdlibc++.so.5 shared library could not be found. Ignoring
> version dependency problems for the moment, I would expect
> that a simple console-mode program would be self-contained
> and should not require any external libraries once compiled.

Take this very simple program:
#include <iostream>

int main(){
  std::cout << "hello" << std::endl;
  return 0;
}

Compiled with `g++ ex.cpp`

The results of ldd show that it definitely does depend on shared
libraries:
 `ldd a.out` :
        libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x40027000)
        libm.so.6 => /lib/tls/libm.so.6 (0x400e1000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x40105000)
        libc.so.6 => /lib/tls/libc.so.6 (0x4010e000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

That means my simple example depends on these packages:
libc6
libstdc++5
libgcc1

If I compiled it with the -static flag: `g++ ex.cpp -static`, ldd shows
no dependencies (like you'd expect).

The cost of this is an executable size of 1069155 bytes as opposed to
13976 for the dynamically linked one.


>  
> So first, can anybody tell me if that is correct, or would a simple
> "Hello World" program require run-time linkage with resident
> libraries on its host system? (If it does, Linux loses many
> points in my opinion.)

My understanding is Win32 does the same thing. I haven't tested this
theory but I do know there are a whole lot of "external dependencies" in
the project settings of a VC++ project.

>  Of course the login shell on the shared
> host is running in a chroot jail.
>  
> Second, could the chroot jail be the cause of the problem?
> This seems like a ridiculous obstacle to something that 
> should be very simple.

I couldn't say.

Bart

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