Annotation of gforth/libcc.fs, revision 1.32

1.1       anton       1: \ libcc.fs     foreign function interface implemented using a C compiler
                      2: 
1.27      anton       3: \ Copyright (C) 2006,2007 Free Software Foundation, Inc.
1.1       anton       4: 
                      5: \ This file is part of Gforth.
                      6: 
                      7: \ Gforth is free software; you can redistribute it and/or
                      8: \ modify it under the terms of the GNU General Public License
1.28      anton       9: \ as published by the Free Software Foundation, either version 3
1.1       anton      10: \ of the License, or (at your option) any later version.
                     11: 
                     12: \ This program is distributed in the hope that it will be useful,
                     13: \ but WITHOUT ANY WARRANTY; without even the implied warranty of
                     14: \ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                     15: \ GNU General Public License for more details.
                     16: 
                     17: \ You should have received a copy of the GNU General Public License
1.28      anton      18: \ along with this program. If not, see http://www.gnu.org/licenses/.
1.1       anton      19: 
                     20: 
                     21: \ What this implementation does is this: if it sees a declaration like
                     22: 
1.2       anton      23: \ \ something that tells it that the current library is libc
1.6       anton      24: \ \c #include <unistd.h>
1.2       anton      25: \ c-function dlseek lseek n d n -- d
1.1       anton      26: 
                     27: \ it genererates C code similar to the following:
                     28: 
                     29: \ #include <gforth.h>
1.2       anton      30: \ #include <unistd.h>
1.1       anton      31: \ 
1.2       anton      32: \ void gforth_c_lseek_ndn_d(void)
1.1       anton      33: \ {
                     34: \   Cell *sp = gforth_SP;
                     35: \   Float *fp = gforth_FP;
1.2       anton      36: \   long long result;  /* longest type in C */
                     37: \   gforth_ll2d(lseek(sp[3],gforth_d2ll(sp[2],sp[1]),sp[0]),sp[3],sp[2]);
                     38: \   gforth_SP = sp+2;
1.1       anton      39: \ }
                     40: 
                     41: \ Then it compiles this code and dynamically links it into the Gforth
                     42: \ system (batching and caching are future work).  It also dynamically
                     43: \ links lseek.  Performing DLSEEK then puts the function pointer of
1.2       anton      44: \ the function pointer of gforth_c_lseek_ndn_d on the stack and
                     45: \ calls CALL-C.
                     46: 
1.7       anton      47: \ ToDo:
                     48: 
                     49: \ Batching, caching and lazy evaluation:
                     50: 
                     51: \ Batching:
                     52: 
                     53: \ New words are deferred, and the corresponding C functions are
                     54: \ collected in one file, until the first word is EXECUTEd; then the
                     55: \ file is compiled and linked into the system, and the word is
                     56: \ resolved.
                     57: 
                     58: \ Caching:
                     59: 
                     60: \ Instead of compiling all this stuff anew for every execution, we
                     61: \ keep the files around and have an index file containing the function
                     62: \ names and their corresponding .so files.  If the needed wrapper name
                     63: \ is already present, it is just linked instead of generating the
                     64: \ wrapper again.  This is all done by loading the index file(s?),
                     65: \ which define words for the wrappers in a separate wordlist.
                     66: 
                     67: \ The files are built in .../lib/gforth/$VERSION/libcc/ or
                     68: \ ~/.gforth/libcc/$HOST/.
                     69: 
1.2       anton      70: \ other things to do:
                     71: 
                     72: \ c-variable forth-name c-name
                     73: \ c-constant forth-name c-name
                     74: 
1.20      anton      75: \ Todo: conversion between function pointers and xts (both directions)
                     76: 
                     77: \ taking an xt and turning it into a function pointer:
                     78: 
                     79: \ e.g., assume we have the xt of + and want to create a C function int
                     80: \ gforth_callback_plus(int, int), and then pass the pointer to that
                     81: \ function:
                     82: 
                     83: \ There should be Forth code like this:
                     84: \   ] + 0 (bye)
                     85: \ Assume that the start of this code is START
                     86:         
                     87: \ Now, there should be a C function:
                     88: 
                     89: \ int gforth_callback_plus(int p1, int p2)
                     90: \ {
                     91: \   Cell   *sp = gforth_SP;
                     92: \   Float  *fp = gforth_FP;
                     93: \   Float  *fp = gforth_FP;
                     94: \   Address lp = gforth_LP;
                     95: \   sp -= 2;
                     96: \   sp[0] = p1;
                     97: \   sp[1] = p2;
                     98: \   gforth_engine(START, sp, rp, fp, lp);
                     99: \   sp += 1;
                    100: \   gforth_RP = rp;
                    101: \   gforth_SP = sp;
                    102: \   gforth_FP = fp;
                    103: \   gforth_LP = lp;
                    104: \   return sp[0];
                    105: \ }
                    106: 
                    107: \ and the pointer to that function is the C function pointer for the XT of +.
                    108: 
                    109: \ Future problems:
                    110: \   how to combine the Forth code generation with inlining
                    111: \   START is not a constant across executions (when caching the C files)
                    112: \      Solution: make START a variable, and store into it on startup with dlsym
                    113: 
                    114: \ Syntax:
                    115: \  callback <rettype> <params> <paramtypes> -- <rettype>
                    116: 
1.2       anton     117: 
                    118: \ data structures
                    119: 
1.10      anton     120: \ For every c-function, we have three words: two anonymous words
                    121: \ created by c-function-ft (first time) and c-function-rt (run-time),
                    122: \ and a named deferred word.  The deferred word first points to the
                    123: \ first-time word, then to the run-time word; the run-time word calls
                    124: \ the c function.
                    125: 
1.29      anton     126: [ifundef] parse-name
                    127:     ' parse-word alias parse-name
                    128: [then]
                    129: [ifundef] defer!
                    130: : defer! ( xt xt-deferred -- ) \ gforth  defer-store
                    131: \G Changes the @code{defer}red word @var{xt-deferred} to execute @var{xt}.
                    132:     >body [ has? rom [IF] ] @ [ [THEN] ] ! ;
                    133: [then]
                    134: 
                    135: \ : delete-file 2drop 0 ;
1.12      anton     136: 
                    137: require struct.fs
                    138: 
                    139:     \ counted-string
                    140:     
1.10      anton     141: \ c-function-ft word body:
1.12      anton     142: struct
                    143:     cell% field cff-cfr \ xt of c-function-rt word
                    144:     cell% field cff-deferred \ xt of c-function deferred word
                    145:     cell% field cff-lha \ address of the lib-handle for the lib that
                    146:                         \ contains the wrapper function of the word
                    147:     char% field cff-rtype  \ return type
                    148:     char% field cff-np     \ number of parameters
                    149:     1 0   field cff-ptypes \ #npar parameter types
                    150:     \  counted string: c-name
                    151: end-struct cff%
                    152: 
1.14      anton     153: variable c-source-file-id \ contains the source file id of the current batch
                    154: 0 c-source-file-id !
                    155: variable lib-handle-addr \ points to the library handle of the current batch.
                    156:                          \ the library handle is 0 if the current
                    157:                          \ batch is not yet compiled.
1.23      anton     158: 2variable lib-filename   \ filename without extension
                    159: 2variable lib-modulename \ basename of the file without extension
1.2       anton     160: 
1.3       anton     161: : .nb ( n -- )
1.2       anton     162:     0 .r ;
                    163: 
                    164: : const+ ( n1 "name" -- n2 )
                    165:     dup constant 1+ ;
                    166: 
1.10      anton     167: : front-string { c-addr1 u1 c-addr2 u2 -- c-addr3 u3 }
                    168:     \ insert string c-addr2 u2 in buffer c-addr1 u1; c-addr3 u3 is the
                    169:     \ remainder of the buffer.
                    170:     assert( u1 u2 u>= )
                    171:     c-addr2 c-addr1 u2 move
                    172:     c-addr1 u1 u2 /string ;
                    173: 
                    174: : front-char { c-addr1 u1 c -- c-addr3 u2 }
                    175:     \ insert c in buffer c-addr1 u1; c-addr3 u3 is the remainder of
                    176:     \ the buffer.
                    177:     assert( u1 0 u> )
                    178:     c c-addr1 c!
                    179:     c-addr1 u1 1 /string ;
                    180: 
1.15      anton     181: : s+ { addr1 u1 addr2 u2 -- addr u }
                    182:     u1 u2 + allocate throw { addr }
                    183:     addr1 addr u1 move
                    184:     addr2 addr u1 + u2 move
                    185:     addr u1 u2 +
                    186: ;
                    187: 
                    188: : append { addr1 u1 addr2 u2 -- addr u }
                    189:     addr1 u1 u2 + dup { u } resize throw { addr }
                    190:     addr2 addr u1 + u2 move
                    191:     addr u ;
                    192: 
1.6       anton     193: \ linked list stuff (should go elsewhere)
                    194: 
                    195: struct
                    196:     cell% field list-next
                    197:     1 0   field list-payload
                    198: end-struct list%
                    199: 
                    200: : list-insert { node list -- }
                    201:     list list-next @ node list-next !
                    202:     node list list-next ! ;
                    203: 
                    204: : list-append { node endlistp -- }
                    205:     \ insert node at place pointed to by endlistp
                    206:     node endlistp @ list-insert
                    207:     node list-next endlistp ! ;
                    208: 
                    209: : list-map ( ... list xt -- ... )
                    210:     \ xt ( ... node -- ... )
                    211:     { xt } begin { node }
                    212:        node while
                    213:            node xt execute
                    214:            node list-next @
                    215:     repeat ;
                    216: 
                    217: \ C prefix lines
                    218: 
                    219: \ linked list of longcstrings: [ link | count-cell | characters ]
                    220: 
                    221: list%
                    222:     cell% field c-prefix-count
                    223:     1 0   field c-prefix-chars
                    224: end-struct c-prefix%
                    225: 
                    226: variable c-prefix-lines 0 c-prefix-lines !
                    227: variable c-prefix-lines-end c-prefix-lines c-prefix-lines-end !
                    228: 
1.14      anton     229: : print-c-prefix-line ( node -- )
                    230:     dup c-prefix-chars swap c-prefix-count @ type cr ;
                    231: 
                    232: : print-c-prefix-lines ( -- )
                    233:     c-prefix-lines @ ['] print-c-prefix-line list-map ;
                    234: 
1.6       anton     235: : save-c-prefix-line ( c-addr u -- )
1.14      anton     236:     c-source-file-id @ ?dup-if
                    237:        >r 2dup r> write-line throw
                    238:     then
1.6       anton     239:     align here 0 , c-prefix-lines-end list-append ( c-addr u )
                    240:     longstring, ;
                    241: 
1.18      anton     242: : \c ( "rest-of-line" -- ) \ gforth backslash-c
1.17      anton     243:     \G One line of C declarations for the C interface
1.6       anton     244:     -1 parse save-c-prefix-line ;
                    245: 
1.19      anton     246: s" #include <gforth/" version-string s+ s" /libcc.h>" append ( c-addr u )
                    247:   2dup save-c-prefix-line drop free throw
1.5       anton     248: 
1.6       anton     249: \ Types (for parsing)
1.5       anton     250: 
1.2       anton     251: wordlist constant libcc-types
                    252: 
                    253: get-current libcc-types set-current
                    254: 
                    255: \ index values
                    256: -1
                    257: const+ -- \ end of arguments
                    258: const+ n \ integer cell
1.5       anton     259: const+ a \ address cell
1.2       anton     260: const+ d \ double
                    261: const+ r \ float
                    262: const+ func \ C function pointer
                    263: const+ void
                    264: drop
                    265: 
                    266: set-current
                    267: 
                    268: : parse-libcc-type ( "libcc-type" -- u )
                    269:     parse-name libcc-types search-wordlist 0= -13 and throw execute ;
                    270: 
                    271: : parse-function-types ( "{libcc-type}" "--" "libcc-type" -- )
                    272:     here 2 chars allot here begin
                    273:        parse-libcc-type dup 0>= while
                    274:            c,
                    275:     repeat
1.3       anton     276:     drop here swap - over char+ c!
                    277:     parse-libcc-type dup 0< -32 and throw swap c! ;
1.2       anton     278: 
                    279: : type-letter ( n -- c )
1.5       anton     280:     chars s" nadrfv" drop + c@ ;
1.2       anton     281: 
                    282: \ count-stacks
                    283: 
                    284: : count-stacks-n ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
                    285:     1+ ;
                    286: 
1.5       anton     287: : count-stacks-a ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
1.2       anton     288:     1+ ;
                    289: 
                    290: : count-stacks-d ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
                    291:     2 + ;
                    292: 
                    293: : count-stacks-r ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
                    294:     swap 1+ swap ;
                    295: 
                    296: : count-stacks-func ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
                    297:     1+ ;
                    298: 
                    299: : count-stacks-void ( fp-change1 sp-change1 -- fp-change2 sp-change2 )
                    300: ;
                    301: 
                    302: create count-stacks-types
                    303: ' count-stacks-n ,
1.5       anton     304: ' count-stacks-a ,
1.2       anton     305: ' count-stacks-d ,
                    306: ' count-stacks-r ,
                    307: ' count-stacks-func ,
                    308: ' count-stacks-void ,
                    309: 
                    310: : count-stacks ( pars -- fp-change sp-change )
                    311:     \ pars is an addr u pair
                    312:     0 0 2swap over + swap u+do
1.3       anton     313:        i c@ cells count-stacks-types + @ execute
1.2       anton     314:     loop ;
                    315: 
                    316: \ gen-pars
                    317: 
                    318: : gen-par-n ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
1.5       anton     319:     ." sp[" 1- dup .nb ." ]" ;
1.2       anton     320: 
1.5       anton     321: : gen-par-a ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
1.2       anton     322:     ." (void *)(" gen-par-n ." )" ;
                    323: 
                    324: : gen-par-d ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
1.4       anton     325:     ." gforth_d2ll(" gen-par-n ." ," gen-par-n ." )" ;
1.2       anton     326: 
                    327: : gen-par-r ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
1.3       anton     328:     swap 1- tuck ." fp[" .nb ." ]" ;
1.2       anton     329: 
                    330: : gen-par-func ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
1.5       anton     331:     gen-par-a ;
1.2       anton     332: 
                    333: : gen-par-void ( fp-depth1 sp-depth1 -- fp-depth2 sp-depth2 )
                    334:     -32 throw ;
                    335: 
                    336: create gen-par-types
                    337: ' gen-par-n ,
1.5       anton     338: ' gen-par-a ,
1.2       anton     339: ' gen-par-d ,
                    340: ' gen-par-r ,
                    341: ' gen-par-func ,
                    342: ' gen-par-void ,
                    343: 
                    344: : gen-par ( fp-depth1 sp-depth1 partype -- fp-depth2 sp-depth2 )
1.3       anton     345:     cells gen-par-types + @ execute ;
1.2       anton     346: 
                    347: \ the call itself
                    348: 
                    349: : gen-wrapped-call { d: pars d: c-name fp-change1 sp-change1 -- }
                    350:     c-name type ." ("
1.3       anton     351:     fp-change1 sp-change1 pars over + swap u+do 
1.2       anton     352:        i c@ gen-par
                    353:        i 1+ i' < if
                    354:            ." ,"
                    355:        endif
                    356:     loop
                    357:     2drop ." )" ;
                    358: 
                    359: \ calls for various kinds of return values
                    360: 
                    361: : gen-wrapped-void ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
                    362:     2dup 2>r gen-wrapped-call 2r> ;
                    363: 
1.3       anton     364: : gen-wrapped-n ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
1.5       anton     365:     2dup gen-par-n 2>r ." =" gen-wrapped-call 2r> ;
1.3       anton     366: 
1.5       anton     367: : gen-wrapped-a ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
                    368:     2dup gen-par-n 2>r ." =(Cell)" gen-wrapped-call 2r> ;
1.3       anton     369: 
                    370: : gen-wrapped-d ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
                    371:     ." gforth_ll2d(" gen-wrapped-void
1.5       anton     372:     ." ," gen-par-n ." ," gen-par-n ." )" ;
1.3       anton     373: 
                    374: : gen-wrapped-r ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
1.30      anton     375:     2dup gen-par-r 2>r ." =" gen-wrapped-call 2r> ;
1.3       anton     376: 
                    377: : gen-wrapped-func ( pars c-name fp-change1 sp-change1 -- fp-change sp-change )
1.5       anton     378:     gen-wrapped-a ;
1.3       anton     379: 
1.2       anton     380: create gen-wrapped-types
                    381: ' gen-wrapped-n ,
1.5       anton     382: ' gen-wrapped-a ,
1.2       anton     383: ' gen-wrapped-d ,
                    384: ' gen-wrapped-r ,
                    385: ' gen-wrapped-func ,
                    386: ' gen-wrapped-void ,
                    387: 
                    388: : gen-wrapped-stmt ( pars c-name fp-change1 sp-change1 ret -- fp-change sp-change )
1.3       anton     389:     cells gen-wrapped-types + @ execute ;
1.2       anton     390: 
1.10      anton     391: : wrapper-function-name ( addr -- c-addr u )
                    392:     \ addr points to the return type index of a c-function descriptor
                    393:     count { r-type } count { d: pars }
                    394:     pars + count { d: c-name }
                    395:     s" gforth_c_" { d: prefix }
                    396:     prefix nip c-name nip + pars nip + 3 + { u }
                    397:     u allocate throw { c-addr }
                    398:     c-addr u
                    399:     prefix front-string c-name front-string '_ front-char
                    400:     pars bounds u+do
                    401:        i c@ type-letter front-char
                    402:     loop
                    403:     '_ front-char r-type type-letter front-char assert( dup 0= )
                    404:     2drop c-addr u ;
                    405: 
1.2       anton     406: : gen-wrapper-function ( addr -- )
                    407:     \ addr points to the return type index of a c-function descriptor
1.10      anton     408:     dup { descriptor }
1.13      anton     409:     count { ret } count 2dup { d: pars } chars + count { d: c-name }
1.23      anton     410:     ." void " lib-modulename 2@ type ." _LTX_" descriptor wrapper-function-name 2dup type drop free throw
1.10      anton     411:     .\" (void)\n"
1.4       anton     412:     .\" {\n  Cell MAYBE_UNUSED *sp = gforth_SP;\n  Float MAYBE_UNUSED *fp = gforth_FP;\n  "
1.2       anton     413:     pars c-name 2over count-stacks ret gen-wrapped-stmt .\" ;\n"
                    414:     ?dup-if
1.3       anton     415:        ."   gforth_SP = sp+" .nb .\" ;\n"
1.2       anton     416:     endif
                    417:     ?dup-if
1.3       anton     418:        ."   gforth_FP = fp+" .nb .\" ;\n"
1.2       anton     419:     endif
1.3       anton     420:     .\" }\n" ;
1.2       anton     421: 
1.16      anton     422: : tempdir ( -- c-addr u )
                    423:     s" TMPDIR" getenv dup 0= if
                    424:         2drop s" /tmp"
                    425:     then ;
                    426: 
1.15      anton     427: : gen-filename ( x -- c-addr u )
                    428:     \ generates a filename without extension for lib-handle-addr X
1.16      anton     429:     0 <<# ['] #s $10 base-execute #> 
1.23      anton     430:     tempdir s" /gforth_c_" s+ 2swap append #>> ;
1.15      anton     431: 
1.12      anton     432: : init-c-source-file ( -- )
                    433:     c-source-file-id @ 0= if
1.23      anton     434:         here 0 , dup lib-handle-addr ! gen-filename 2dup lib-filename 2!
                    435:         2dup tempdir nip 1+ /string lib-modulename 2!
1.15      anton     436:        s" .c" s+ 2dup w/o create-file throw dup c-source-file-id !
                    437:         ['] print-c-prefix-lines swap outfile-execute
                    438:         drop free throw
1.12      anton     439:     endif ;
1.11      anton     440: 
                    441: : c-source-file ( -- file-id )
1.12      anton     442:     c-source-file-id @ assert( dup ) ;
1.11      anton     443: 
1.24      anton     444: : .lib-error ( -- )
                    445:     [ifdef] lib-error
                    446:         ['] cr stderr outfile-execute
1.31      anton     447:         lib-error ['] type stderr outfile-execute
1.24      anton     448:     [then] ;
1.23      anton     449: 
1.21      anton     450: DEFER compile-wrapper-function
                    451: :NONAME ( -- )
1.12      anton     452:     c-source-file close-file throw
                    453:     0 c-source-file-id !
1.25      anton     454:     [ libtool-command s"  --silent --mode=compile gcc -I " s+
                    455:     s" includedir" getenv append ] sliteral
1.23      anton     456:     s"  -O -c " s+ lib-filename 2@ append s" .c -o " append
                    457:     lib-filename 2@ append s" .lo" append ( c-addr u )
1.32    ! anton     458: \    cr 2dup type
1.23      anton     459:     2dup system drop free throw $? abort" libtool compile failed"
1.25      anton     460:     [ libtool-command s"  --silent --mode=link gcc -module -rpath " s+ ] sliteral
                    461:     tempdir s+ s"  " append
1.23      anton     462:     lib-filename 2@ append s" .lo -o " append
1.22      anton     463:     lib-filename 2@ append s" .la" append ( c-addr u )
1.23      anton     464:     2dup system drop free throw $? abort" libtool link failed"
                    465:     lib-filename 2@ s" .la" s+
1.31      anton     466: \    2dup type cr
1.23      anton     467:     2dup open-lib dup 0= if
1.24      anton     468:         .lib-error true abort" open-lib failed"
1.23      anton     469:     endif
1.15      anton     470:     ( lib-handle ) lib-handle-addr @ !
                    471:     2dup delete-file throw drop free throw
                    472:     lib-filename 2@ s" .c" s+ 2dup delete-file throw drop free throw
1.21      anton     473:     lib-filename 2@ drop free throw 0 0 lib-filename 2! ; IS compile-wrapper-function
1.5       anton     474: \    s" ar rcs xxx.a xxx.o" system
                    475: \    $? abort" ar generated error" ;
                    476: 
1.12      anton     477: : link-wrapper-function { cff -- sym }
                    478:     cff cff-rtype wrapper-function-name { d: wrapper-name }
1.23      anton     479:     wrapper-name cff cff-lha @ @ assert( dup ) lib-sym dup 0= if
1.24      anton     480:         .lib-error -&32 throw
1.23      anton     481:     endif
1.10      anton     482:     wrapper-name drop free throw ;
1.8       anton     483: 
1.12      anton     484: : c-function-ft ( xt-defr xt-cfr "c-name" "{libcc-type}" "--" "libcc-type" -- )
1.8       anton     485:     \ build time/first time action for c-function
1.12      anton     486:     init-c-source-file
                    487:     noname create 2, lib-handle-addr @ ,
1.2       anton     488:     parse-name { d: c-name }
1.8       anton     489:     here parse-function-types c-name string,
1.11      anton     490:     ['] gen-wrapper-function c-source-file outfile-execute
1.8       anton     491:   does> ( ... -- ... )
1.10      anton     492:     dup 2@ { xt-defer xt-cfr }
1.12      anton     493:     dup cff-lha @ @ 0= if
                    494:        compile-wrapper-function
                    495:     endif
                    496:     link-wrapper-function xt-cfr >body !
1.8       anton     497:     xt-cfr xt-defer defer!
                    498:     xt-cfr execute ;
                    499: 
                    500: : c-function-rt ( -- )
                    501:     \ run-time definition for c function; addr is the address where
                    502:     \ the sym should be stored
                    503:     noname create 0 ,
1.2       anton     504:   does> ( ... -- ... )
                    505:     @ call-c ;
                    506: 
1.18      anton     507: : c-function ( "forth-name" "c-name" "@{type@}" "--" "type" -- ) \ gforth
1.17      anton     508:     \G Define a Forth word @i{forth-name}.  @i{Forth-name} has the
                    509:     \G specified stack effect and calls the C function @code{c-name}.
1.8       anton     510:     defer lastxt dup c-function-rt lastxt c-function-ft
                    511:     lastxt swap defer! ;

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