[PATCH] Ping^4 Define __CORRECT_ISO_CPP_STRING_H_PROTO correctly for Clang.

[Joseph S. Myers]

On Mon, 23 Dec 2013, Ondrej Bilka wrote:

> Joseph, are you ok with this? This is simple addition that could go to 2.19,
> is Brooks rationale sufficient for you?

I'm happy with the principle, given that this doesn't affect the set of 
GCC versions for which this applies.  I believe we have a rule that 
warning-avoidance in installed glibc headers should not depend on warnings 
being disabled in system headers that would not be disabled elsewhere - 
thus, to be clear with -Wundef -Wsystem-headers, the #if condition needs 
to be of the form defined __cplusplus && (__cplusplus >= 199711L || 
__GNUC_PREREQ (4, 4)) (generally, #if conditions in system headers need to 
avoid using the value of a possibly undefined macro).  And we did 
previously (Dec 2012 / Jan 2013) discuss a principle of putting compiler 
feature tests in features.h or sys/cdefs.h and avoiding them in other 
installed headers - but haven't really done anything much to implement 
such a principle.  (It's also less clear such a principle would actually 
be helpful in some cases of optimizations in headers.)

-- 
Joseph S. Myers
joseph@codesourcery.com