Transitioning to gcc 3.2
Transitioning to gcc 3.2
Here is a short FAQ about using the new GCC compiler here at umbc.
Table of Contents
- Why gcc-3.2?
- Important note about C++ libraries.
- A correct HelloWorld.cpp example.
- Using the old version of gcc when all else fails
OIT has released a new version of the GCC compiler suite on all of
central UNIX login machines and Linux lab images. This new version,
GCC 3.2, fixes a lot of bugs present in the old version and contains a
completely revamped C++ subsystem that may cause C++ programs that had
previously compiled to fail under this new version in some
circumstances. This FAQ is meant to help address most of these issues.
The new version of GCC has changed its ABI(Application Binary
Interface) for any C++ generated code. This means that any C++ object
files, programs, and shared libraries which were compiled with
different versions of the compiler will no longer work together.
For instance, if you have a shared lib, libfoo.so, which was built with
gcc v2.95 and is used by a program, bar, which is then built with
gcc v3.2, it will no longer be able to link against libfoo (and vice
versa with the compiler versions). Both libfoo and bar must be
compiled with the same version to correctly function.
THIS DOES NOT AFFECT C CODE, ONLY C++. Libraries and programs written
in C will continue to function regardless of the mix of compiler versions.
One the most notable differences in the new version of GCC is that it
strictly(ie: correctly) enforces the use of namespaces in C++. Therefore symbols
like 'cout' are undefined outside of the scope of the std namespace.
Below is a standards compliant implementation of the classic Hello
World program in C++:
#include <iostream> //notice no .h suffix
using namespace std; //required for resolving the 'cout' symbol
int main(int argc, char *argv[])
{
cout << "Hello World" << endl;
return(0);
}
If you are unable to fix your code to meet the c++ specification, you
can still compile it with the old version of gcc. To do this, simply
change your makefile(or whatever build environment you're using) to
call gcc-2.95 or g++-2.95 and it will be compiled as before.
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