Hi Olly,
On Tue, Feb 15, 2000 at 03:22:49AM +0000, Olly Betts wrote:
> In message <[EMAIL PROTECTED]>, Ossama Othman writes:
> >Something like the following should be a good smoke test:
> >
> > class Foo
> > {
> > public:
> > Foo (void) : bar_ (0) { }
> > virtual ~Foo (void) { }
> > virtual int bar (void) { return this->bar_; }
> > private:
> > int bar_;
> > };
> >
> > int main (int, char *[])
> > {
> > Foo fnord;
> > int a = fnord.bar ();
> > return a;
> > }
>
> Just noticed a problem with this. If you compile it with:
>
> gcc -o test test.cc
Right, I noticed that too. Hopefully `gcc' won't be part of the
C++ compiler search list, unless there is good reason for it.
> You get a working executable called test. But in gcc won't link this
> C++ program:
>
> #include <iostream>
Note that <iostream> still isn't supported by some C++ compilers.
<iostream.h> would have to be used.
> int main() { cout << "hello world\n"; return 0; }
>
> This is what happens (gcc 2.95.2 on Linux):
>
> $ gcc -o a.out test2.cc
> /tmp/ccx2KlXv.o: In function main':
> /tmp/ccx2KlXv.o(.text+0xf): undefined reference to cout'
> /tmp/ccx2KlXv.o(.text+0x14): undefined reference to ostream::operator<<(char const
>*)'
> collect2: ld returned 1 exit status
>
> Both programs compile and run fine when using g++ in place of gcc.
>
> So it looks like the test program probably ought to use at least one
> library function to make sure that the right libraries are getting
> linked in.
>
> Thoughts as to a good candidate?
I'm a bit leary about using library functions, particularly those from
C++ libraries for several reasons:
1. A C++ library may not be installed (believe it or not), or someone
could even supply the following for g++ (for example):
CXX=c++ CXXFLAGS=-nostdlib ./configure
in which case, `libstdc++' wouldn't be linked, and similary for Sun
C++:
CXX=CC CXXFLAGS=-library=no%iostream,no%Cstd ./configure
Admittedly, these are odd configurations but they are certainly valid
configurations.
I don't think we can assume everyone uses the standard C++ library, or
even has it installed.
2. Some standard C++ libraries may actually place functions/classes in
the "std" namespace. For example, the following may potentially be
required for some platforms:
int main() { std::cout << "hello world\n"; return 0; }
This is problem for C++ compilers/libraries that don't provide a "std"
namespace. The following is also problematic:
using namespace std;
int main() { cout << "hello world\n"; return 0; }
Since not all C++ compilers support the "using" keyword, or even
support namespaces via the "namespace" keyword.
It is for these reasons why I didn't include any library functions in
the simple test I posted. My goal for the test was to use C++
features that all C++ compilers should support (base member
initialization, virtual functions and a "this" pointer), that didn't
rely on anything external, such as a library. Unfortunately, I can't
think of any better tests or ideas either; at least not at the
moment. :-)
Thoughts? Disagreements?
-Ossama
--
Ossama Othman <[EMAIL PROTECTED]>
Distributed Object Computing Laboratory, Univ. of California at Irvine
1024D/F7A394A8 - 84ED AA0B 1203 99E4 1068 70E6 5EB7 5E71 F7A3 94A8
