On Mon, May 14, 2012 at 4:19 PM, Guido Muesch <g.mue...@googlemail.com> wrote: > Dear all, > > Is it really intended that ptrdiff_t is 32bit? > I guess not, because the "gcc47: 20-Bit Design" states: > "Memory model target options are accepted only when building for > CPUX-capable MCUs. Compilation for non-CPUX MCUs effectively uses the > small memory model." > And before that about the small memory model was stated: > "size_t and ptrdiff_t are 16 bits, and no data object may exceed 32767 bytes." > > I am referring to mspgcc-20120406-p20120502 (non-CPUX) > > For a quick check how msp430-gcc is configured: > $ msp430-gcc -dM -E - < /dev/null | grep PTRDIFF > #define __PTRDIFF_MAX__ 2147483647L > #define __SIZEOF_PTRDIFF_T__ 4 > #define __PTRDIFF_TYPE__ long int > > In contrast to the AVR gcc: > $ avr-gcc -dM -E - < /dev/null | grep PTRDIFF > #define __PTRDIFF_MAX__ 32767 > #define __SIZEOF_PTRDIFF_T__ 2 > #define __PTRDIFF_TYPE__ int > > I came across this issue when looking at the generated code for int > pointer subtraction. Surprisingly huge code, because a sign extension > and a 32bit subtraction was performed. > However when dealing with a char pointers subtraction (being casted > into an int result) the 32bit operations are optimized away. That > might explain why this has not been noticed yet.
That was a side effect of a major cleanup a little over a year ago; I remember there was various confusion I was trying to resolve, and that one I just ended up leaving it at gcc's default. It never seemed to cause harm or benefit, so it was ignored until it was fixed internally a couple weeks ago. The next release will get it right. Peter > Regards, > Guido > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Mspgcc-users mailing list > Mspgcc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/mspgcc-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Mspgcc-users mailing list Mspgcc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mspgcc-users
