Why does -pedantic make long long an error in C++?

[Matthew Wilcox <willy at debian dot org>]

I just tracked down a build failure in mozilla 1.4.  It has an autoconf
test that does:

$ g++ -o conftest -O -DDEBIAN -fshort-wchar -pthread -pipe  -Wall -Wconversion -Wpointer-arith -Wcast-align -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -pedantic   -I/usr/X11R6/include  conftest.C -ldl -lm
conftest.C: In function `int main()':
conftest.C:6: error: ISO C++ does not support `long long'

(the code in question is the trivial:

int main () {
        if (sizeof(long long) != 8) {
                return 1;
        }
        return 0;
} 
)

My question is: Why is this an error rather than a warning?

The manual says: "to obtain all the diagnostics required by the
standard, you should also specify `-pedantic' (or `-pedantic-errors' if
you want them to be errors rather than warnings)."

So I could make this an error if I wanted to, but I can't make it a warning.
-Wno-error doesn't make it a warning, -Wno-long-long turns off the diagnostic.

gcc (rather than g++) emits this as a warning:

conftest.c:6: warning: ISO C90 does not support `long long'

Surely it's only a matter of time until the ISO C++ committee adds
"long long" to the language anyway?  This seems like a pretty obnoxious
thing to be inflicting on users.

Oh, and I'm using Debian's GCC 3.3.1.

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