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Re: RFC: adding knowledge of the int_fastN_t types to the compiler


On Wed, 12 Mar 2008, Ian Lance Taylor wrote:

> I don't disagree with that, but I would also like to see something
> that will not require changing every target for basic default
> behaviour.
> 
> I'd like to suggest that in the absence of other information from the
> tm.h file, for N in {8,16,32,64}, where N <= UNITS_PER_WORD *
> BITS_PER_UNIT, we map int_fastN_t to int_fastM_t, where M ==
> UNITS_PER_WORD * BITS_PER_UNIT.

Given the ABI implications and the varying rules used to determine these 
types on different targets, I think it would be best not to install 
<stdint.h> from GCC or define any associated internal macros for C code if 
we don't have appropriate definitions of the types for the particular 
target in question.  We can, however, provide defaults of our choice for 
targets that don't have the relevant types at all and won't be updated to 
have them (unmaintained OSes, or targets with OS version numbers for old 
OS versions - in the latter case, types from a newer OS version would be 
an appropriate choice); it's just targets that might have them but haven't 
had the relevant information recorded in GCC that I think should not have 
the types defined by default in GCC.  (How this relates to Fortran is up 
to the Fortran maintainers.)

-- 
Joseph S. Myers
joseph@codesourcery.com


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