when a X @ sequence is entered after $AABBCCDD X ! The interpreter may do a XT_EXECUTE so if $AABBCCDD is on tos x3 register
CODEWORD "execute",EXECUTE mv x17,x3 loadtos j DO_EXECUTE this would spell trouble and give an exception, and the worst part is the loadtos would hide the problem because now x17 is propagating an unexecutable code address being on a byte boundary and a stack dump is not going to show this (.s) This may have been planned as a feature to support the execution of code in ram This is starting to make sense. John S On Mon, Jan 5, 2026 at 4:05 PM John Sarabacha <[email protected]> wrote: > Hi Tristan, > I tried this sequence on ESP32Forth and there were no issues. > > in RISCV > >> variable X > >> creates the structure below in ram > .macro VARIABLE Name, Label > HEADER Flag_visible|Flag_variable, "\Name", \Label, PFA_DOVARIABLE > .word rampointer > .set rampointer, rampointer+4 > .endm > > >> $AABBCCDD X ! > >> rampointer (above) is where the address where $AABBCCDD is stored > > CODEWORD "!", STORE # ( x 32-addr -- ) --> ( $AABBCCDD rampointer-X -- ) > lw x5, 0(x4) x5 (temp reg) is loaded with > rampointer-X from 0(x4) by indexing x4 (Data Stack Pointer) > sw x5, 0(x3) ramponter -X is written to ram location > pointed by address in tos (x3) > lw x3, 4(x4) x3 tos is loaded from 4(x4) indexing of > x4 (now has initial value $AABBCCDD ) > addi x4, x4, 8 Data Stack Pointer is incremented by 8 > NEXT > > This is not behaving as it's description ( x 32-addr -- ) this segment of > code is leaving $AABBCCDD on tos x3 register > whether this is part of the problem ??? > > Regards, > John S > > On Mon, Jan 5, 2026 at 3:28 PM <[email protected]> wrote: > >> Hi John, >> >> Here is the sequence of words working correctly. The results >> would be similar for any 32 bit Forth. Try it on ESP32Forth. >> >> |S| 1|hex >> |S| 2|variable x >> |S| 3|x u. >> |O| 3|20000950 >> |S| 4|aabbccdd x ! >> |S| 5|x @ u. >> |O| 5|AABBCCDD >> |W| 6| >> >> There is no writing to or reading from a misaligned address, >> so whilst it can be a major issue, it is not the issue here. >> >> The issue with with the svn repo code is as described in the >> link. I wanted to mention it as it will raise some questions >> about about flash/ram and dictionary/variable storage that I >> wish I had considered earlier than I did. It seemed a good >> moment given that Martin had just got a prompt on the UNO R4. >> >> Best wishes, >> Tristan >> >> On 2026-01-05 17:36, John Sarabacha wrote: >> > AmForth is doing exactly what it is told to do, looks like the code >> > base is >> > functional, the processor (Cortex-M4/RISCV) is doing what it is >> > supposed to >> > do. It is up to the user to supply the correct information otherwise >> > the >> > processor will complain (exception out). >> > >> > On Mon, Jan 5, 2026 at 12:27 PM John Sarabacha <[email protected]> >> > wrote: >> > >> >> The other possibility is that it is not a valid address that the >> >> processor >> >> can access which could cause an exception >> >> >> >> On Mon, Jan 5, 2026 at 12:18 PM John Sarabacha <[email protected]> >> >> wrote: >> >> >> >>> So when you execute X @ you are trying to indirectly read from the >> >>> address 0xAABBCCDD >> >>> which could cause an exception >> >>> >> >>> On Mon, Jan 5, 2026 at 12:08 PM Martin Kobetic <[email protected]> >> >>> wrote: >> >>> >> >>>> On Mon, Jan 5, 2026 at 11:51 AM John Sarabacha >> >>>> <[email protected]> >> >>>> wrote: >> >>>> >> >>>> > Still learning forth , programmed in many other languages (alot of >> >>>> > assembler) >> >>>> > variable X >> >>>> > $AABBCCDD X ! >> >>>> > X @ >> >>>> > >> >>>> > However tell me if I am wrong, you are creating a variable >> definition >> >>>> for X >> >>>> > you are setting this variable X to the address $AABBCCDD and then >> >>>> trying to >> >>>> > read a value from this >> >>>> > address on to the tos. >> >>>> >> >>>> >> >>>> Almost. The second line is storing value 0xAABBCCDD at the address >> >>>> represented by variable X. >> >>>> It is the word `variable` in previous line that allocates memory for >> >>>> the >> >>>> variable and associates the corresponding >> >>>> address with a new word `X` that simply pushes that address onto the >> >>>> stack >> >>>> when executed. >> >>>> >> >>>> In the test run I quoted above >> >>>> --- >> >>>> > X >> >>>> ok >> >>>> > .s >> >>>> 5 200002B8 200002C4 200002A8 20000288 8 ok >> >>>> --- >> >>>> The address represented by the variable was 0x200002B8, so it was >> >>>> 8-byte >> >>>> aligned, so should be ok alignment-wise. >> >>>> But your hypothesis with alignment issues seems definitely worth >> >>>> checking >> >>>> out as well. >> >>>> >> >>>> Your warning about the fault interrupts is certainly worth heeding, >> >>>> I >> >>>> don't >> >>>> think we do much there on the ARM side. >> >>>> Another thing to follow up on. >> >>>> >> >>>> _______________________________________________ >> >>>> Amforth-devel mailing list for http://amforth.sf.net/ >> >>>> [email protected] >> >>>> https://lists.sourceforge.net/lists/listinfo/amforth-devel >> >>>> >> >>> >> > >> > _______________________________________________ >> > Amforth-devel mailing list for http://amforth.sf.net/ >> > [email protected] >> > https://lists.sourceforge.net/lists/listinfo/amforth-devel >> >> >> _______________________________________________ >> Amforth-devel mailing list for http://amforth.sf.net/ >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/amforth-devel >> > _______________________________________________ Amforth-devel mailing list for http://amforth.sf.net/ [email protected] https://lists.sourceforge.net/lists/listinfo/amforth-devel
