[cfe-dev] Another Newlib v2.5.0 tweak

[Martin J. O'Riordan via cfe-dev]

Recently I had noticed a significant change in the handling of Locales and
Newlib v2.5.0, and this has been address in recent patches to the head
revision of CLang.

 

But I have come across a more subtle change in the handling of '<stdint.h>'
and the '<inttypes.h>' header with Newlib v2.5.0 versus v2.2.0.

 

In this case the "portable" formatting macros such as 'PRIx64' suddenly
stopped working when I switched to Newlib v2.5.0 from Newlib v2.2.0 for our
"free-standing" target.

 

Most of the ISO C headers we use come from Newlib, but the '<stdint.h>' that
we use comes from CLang ('clang/lib/Headers/stdint.h'), and this has a
subtle incompatibility with the other headers from Newlib v2.5.0 such as
'<inttypes.h>', in that the macro '__int64_t_defined' is no longer defined
as a consequence of other changes in Newlib, but which is defined if I use
the Newlib version of '<stdint.h>'.  However, I find the CLang version of
this header more reliable and prefer to use it.

 

There is a very simple change which can be made to CLang's '<stdint.h>' that
works with Newlib v2.5.0 and which is also backward compatible with older
versions of Newlib, and that is to add the following to CLang's '<stdint.h>'
in the '#else' clause for the Free-standing vs Hosted check (Line 104 in the
CLang v4.0.0 release sources):

 

#ifdef __NEWLIB__

# include <sys/_stdint.h>

#endif /* __NEWLIB__ */

 

I have tested this with Newlib v2.2.0 and v2.5.0, and after visual
inspection I see no reason that it will not work for all versions of Newlib
in between.  I have not checked older versions of Newlib.  Also, since I am
not building a Hosted compiler, I have not checked if a similar change is
necessary for the hosted case.

 

All the best,

 

            MartinO

 

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