Hi Kim,
On 16/04/2015 2:26 PM, Kim Barrett wrote:
This might be of interest:
https://gcc.gnu.org/gcc-4.4/porting_to.html
Preprocessor conditionals always evaluated
Also see this:
http://lists.boost.org/Archives/boost/2011/08/184657.php
—————
This has come up before. The problem is with code like this:
#if !defined(SOMETHING)
#elif SOMETHING() == 1
#endif
In recent versions of gcc it fails when SOMETHING isn't defined
because the 'SOMETHING() == 1' clause is always evaluated - even
though the if statement has already been resolved. This is apparently
compliant with the standard.
The solution is to write:
#if !defined(SOMETHING)
#else
# if SOMETHING() == 1
# endif
#endif
——————
That same technique could be applied by us, as an alternative to the proposed
changes.
But it’s pretty annoying ugly, with sometimes long string of trailing #endif
lines.
Thanks for all the additional information.
So it seems to me there are two choices here:
a) Use the change proposed but verify that the variables concerned are
ones that if defined will never be defined to be zero (which I believe
to be the case but may have trouble proving :( )
b) Replace the 'elif XXX' with 'else ifdef XXX'
For the few cases involved here (b) seems the easier path.
David
