Intel compiler 8.0 pretends to be gcc 3.2.

[Martin Buchholz]

You folks should be aware that gcc is no longer the only compiler that
defines __GNUC__.  Version 8 of icc for Linux does this as well.

In addition to defining the expected macro

__INTEL_COMPILER

it also defines these surprising macros:

    -D__GNUC__=3 \
    -D__GNUC_MINOR__=2 \
    -D__GNUC_PATCHLEVEL__=0 \
    -D__GNUG__=3 \

Given the high degree of gcc-compatibility that icc attains, these
definitions are understandable, but likely to be controversial.

The test

#ifdef __GNUC__

no longer conclusively identifies gcc.

I have had to change one such test to

#if defined (__GNUC__) && !defined (__INTEL_COMPILER)

to enable compilation with both gcc and icc in my own code,
where icc's emulation of gcc is imperfect.

(Prerelease versions of icc 8 are available from intel.com)

Martin