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Annotation of mandoc/mandoc.3, Revision 1.33

1.33    ! schwarze    1: .\"    $Id: mandoc.3,v 1.32 2015/07/19 06:05:16 schwarze Exp $
1.1       kristaps    2: .\"
                      3: .\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
1.31      schwarze    4: .\" Copyright (c) 2010, 2013, 2014, 2015 Ingo Schwarze <schwarze@openbsd.org>
1.1       kristaps    5: .\"
                      6: .\" Permission to use, copy, modify, and distribute this software for any
                      7: .\" purpose with or without fee is hereby granted, provided that the above
                      8: .\" copyright notice and this permission notice appear in all copies.
                      9: .\"
                     10: .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
                     11: .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
                     12: .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
                     13: .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
                     14: .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
                     15: .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
                     16: .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
                     17: .\"
1.33    ! schwarze   18: .Dd $Mdocdate: July 19 2015 $
1.1       kristaps   19: .Dt MANDOC 3
                     20: .Os
                     21: .Sh NAME
                     22: .Nm mandoc ,
1.25      schwarze   23: .Nm man_deroff ,
1.1       kristaps   24: .Nm man_meta ,
1.14      kristaps   25: .Nm man_mparse ,
1.1       kristaps   26: .Nm man_node ,
1.25      schwarze   27: .Nm mdoc_deroff ,
1.1       kristaps   28: .Nm mdoc_meta ,
                     29: .Nm mdoc_node ,
                     30: .Nm mparse_alloc ,
                     31: .Nm mparse_free ,
1.14      kristaps   32: .Nm mparse_getkeep ,
                     33: .Nm mparse_keep ,
1.26      schwarze   34: .Nm mparse_open ,
1.1       kristaps   35: .Nm mparse_readfd ,
                     36: .Nm mparse_reset ,
1.2       kristaps   37: .Nm mparse_result ,
                     38: .Nm mparse_strerror ,
                     39: .Nm mparse_strlevel
1.1       kristaps   40: .Nd mandoc macro compiler library
                     41: .Sh SYNOPSIS
1.25      schwarze   42: .In sys/types.h
1.1       kristaps   43: .In mandoc.h
1.31      schwarze   44: .Pp
1.24      schwarze   45: .Fd "#define ASCII_NBRSP"
                     46: .Fd "#define ASCII_HYPH"
                     47: .Fd "#define ASCII_BREAK"
1.25      schwarze   48: .Ft struct mparse *
1.1       kristaps   49: .Fo mparse_alloc
1.25      schwarze   50: .Fa "int options"
1.1       kristaps   51: .Fa "enum mandoclevel wlevel"
1.23      schwarze   52: .Fa "mandocmsg mmsg"
                     53: .Fa "char *defos"
1.1       kristaps   54: .Fc
                     55: .Ft void
1.24      schwarze   56: .Fo (*mandocmsg)
                     57: .Fa "enum mandocerr errtype"
                     58: .Fa "enum mandoclevel level"
                     59: .Fa "const char *file"
                     60: .Fa "int line"
                     61: .Fa "int col"
                     62: .Fa "const char *msg"
                     63: .Fc
                     64: .Ft void
1.1       kristaps   65: .Fo mparse_free
                     66: .Fa "struct mparse *parse"
                     67: .Fc
1.23      schwarze   68: .Ft const char *
1.14      kristaps   69: .Fo mparse_getkeep
                     70: .Fa "const struct mparse *parse"
                     71: .Fc
                     72: .Ft void
                     73: .Fo mparse_keep
                     74: .Fa "struct mparse *parse"
                     75: .Fc
1.1       kristaps   76: .Ft "enum mandoclevel"
1.26      schwarze   77: .Fo mparse_open
                     78: .Fa "struct mparse *parse"
                     79: .Fa "int *fd"
                     80: .Fa "const char *fname"
                     81: .Fc
                     82: .Ft "enum mandoclevel"
1.1       kristaps   83: .Fo mparse_readfd
                     84: .Fa "struct mparse *parse"
                     85: .Fa "int fd"
                     86: .Fa "const char *fname"
                     87: .Fc
                     88: .Ft void
                     89: .Fo mparse_reset
                     90: .Fa "struct mparse *parse"
                     91: .Fc
                     92: .Ft void
                     93: .Fo mparse_result
                     94: .Fa "struct mparse *parse"
                     95: .Fa "struct mdoc **mdoc"
                     96: .Fa "struct man **man"
1.25      schwarze   97: .Fa "char **sodest"
1.2       kristaps   98: .Fc
                     99: .Ft "const char *"
                    100: .Fo mparse_strerror
                    101: .Fa "enum mandocerr"
                    102: .Fc
                    103: .Ft "const char *"
                    104: .Fo mparse_strlevel
                    105: .Fa "enum mandoclevel"
1.1       kristaps  106: .Fc
1.25      schwarze  107: .In sys/types.h
1.24      schwarze  108: .In mandoc.h
                    109: .In mdoc.h
1.25      schwarze  110: .Ft void
                    111: .Fo mdoc_deroff
                    112: .Fa "char **dest"
                    113: .Fa "const struct mdoc_node *node"
                    114: .Fc
1.24      schwarze  115: .Ft "const struct mdoc_meta *"
                    116: .Fo mdoc_meta
                    117: .Fa "const struct mdoc *mdoc"
                    118: .Fc
                    119: .Ft "const struct mdoc_node *"
                    120: .Fo mdoc_node
                    121: .Fa "const struct mdoc *mdoc"
                    122: .Fc
1.1       kristaps  123: .Vt extern const char * const * mdoc_argnames;
                    124: .Vt extern const char * const * mdoc_macronames;
1.25      schwarze  125: .In sys/types.h
1.24      schwarze  126: .In mandoc.h
                    127: .In man.h
1.25      schwarze  128: .Ft void
                    129: .Fo man_deroff
                    130: .Fa "char **dest"
                    131: .Fa "const struct man_node *node"
                    132: .Fc
1.24      schwarze  133: .Ft "const struct man_meta *"
                    134: .Fo man_meta
                    135: .Fa "const struct man *man"
                    136: .Fc
                    137: .Ft "const struct mparse *"
                    138: .Fo man_mparse
                    139: .Fa "const struct man *man"
                    140: .Fc
                    141: .Ft "const struct man_node *"
                    142: .Fo man_node
                    143: .Fa "const struct man *man"
                    144: .Fc
                    145: .Vt extern const char * const * man_macronames;
1.1       kristaps  146: .Sh DESCRIPTION
                    147: The
                    148: .Nm mandoc
                    149: library parses a
                    150: .Ux
                    151: manual into an abstract syntax tree (AST).
                    152: .Ux
                    153: manuals are composed of
                    154: .Xr mdoc 7
                    155: or
                    156: .Xr man 7 ,
                    157: and may be mixed with
                    158: .Xr roff 7 ,
                    159: .Xr tbl 7 ,
                    160: and
                    161: .Xr eqn 7
                    162: invocations.
                    163: .Pp
                    164: The following describes a general parse sequence:
                    165: .Bl -enum
                    166: .It
                    167: initiate a parsing sequence with
1.27      schwarze  168: .Xr mchars_alloc 3
                    169: and
1.1       kristaps  170: .Fn mparse_alloc ;
                    171: .It
1.31      schwarze  172: open a file with
                    173: .Xr open 2
                    174: or
                    175: .Fn mparse_open ;
                    176: .It
                    177: parse it with
1.1       kristaps  178: .Fn mparse_readfd ;
                    179: .It
1.31      schwarze  180: retrieve the syntax tree with
1.1       kristaps  181: .Fn mparse_result ;
                    182: .It
                    183: iterate over parse nodes with
                    184: .Fn mdoc_node
                    185: or
                    186: .Fn man_node ;
                    187: .It
                    188: free all allocated memory with
1.27      schwarze  189: .Fn mparse_free
                    190: and
                    191: .Xr mchars_free 3 ,
1.1       kristaps  192: or invoke
                    193: .Fn mparse_reset
                    194: and parse new files.
1.3       kristaps  195: .El
                    196: .Sh REFERENCE
                    197: This section documents the functions, types, and variables available
                    198: via
1.25      schwarze  199: .In mandoc.h ,
                    200: with the exception of those documented in
                    201: .Xr mandoc_escape 3
                    202: and
                    203: .Xr mchars_alloc 3 .
1.3       kristaps  204: .Ss Types
                    205: .Bl -ohang
                    206: .It Vt "enum mandocerr"
1.31      schwarze  207: An error or warning message during parsing.
1.3       kristaps  208: .It Vt "enum mandoclevel"
1.11      kristaps  209: A classification of an
1.23      schwarze  210: .Vt "enum mandocerr"
1.11      kristaps  211: as regards system operation.
1.3       kristaps  212: .It Vt "struct mparse"
1.11      kristaps  213: An opaque pointer to a running parse sequence.
                    214: Created with
                    215: .Fn mparse_alloc
                    216: and freed with
                    217: .Fn mparse_free .
                    218: This may be used across parsed input if
                    219: .Fn mparse_reset
                    220: is called between parses.
1.3       kristaps  221: .It Vt "mandocmsg"
1.31      schwarze  222: A prototype for a function to handle error and warning
1.11      kristaps  223: messages emitted by the parser.
1.3       kristaps  224: .El
                    225: .Ss Functions
                    226: .Bl -ohang
1.25      schwarze  227: .It Fn man_deroff
                    228: Obtain a text-only representation of a
                    229: .Vt struct man_node ,
                    230: including text contained in its child nodes.
                    231: To be used on children of the pointer returned from
                    232: .Fn man_node .
                    233: When it is no longer needed, the pointer returned from
                    234: .Fn man_deroff
                    235: can be passed to
                    236: .Xr free 3 .
1.3       kristaps  237: .It Fn man_meta
1.25      schwarze  238: Obtain the meta-data of a successful
                    239: .Xr man 7
                    240: parse.
1.4       kristaps  241: This may only be used on a pointer returned by
                    242: .Fn mparse_result .
1.18      schwarze  243: Declared in
                    244: .In man.h ,
                    245: implemented in
                    246: .Pa man.c .
1.14      kristaps  247: .It Fn man_mparse
                    248: Get the parser used for the current output.
1.18      schwarze  249: Declared in
                    250: .In man.h ,
                    251: implemented in
                    252: .Pa man.c .
1.3       kristaps  253: .It Fn man_node
1.25      schwarze  254: Obtain the root node of a successful
                    255: .Xr man 7
                    256: parse.
1.4       kristaps  257: This may only be used on a pointer returned by
                    258: .Fn mparse_result .
1.18      schwarze  259: Declared in
                    260: .In man.h ,
                    261: implemented in
                    262: .Pa man.c .
1.25      schwarze  263: .It Fn mdoc_deroff
                    264: Obtain a text-only representation of a
                    265: .Vt struct mdoc_node ,
                    266: including text contained in its child nodes.
                    267: To be used on children of the pointer returned from
                    268: .Fn mdoc_node .
                    269: When it is no longer needed, the pointer returned from
                    270: .Fn mdoc_deroff
                    271: can be passed to
                    272: .Xr free 3 .
1.3       kristaps  273: .It Fn mdoc_meta
1.25      schwarze  274: Obtain the meta-data of a successful
                    275: .Xr mdoc
                    276: parse.
1.4       kristaps  277: This may only be used on a pointer returned by
                    278: .Fn mparse_result .
1.18      schwarze  279: Declared in
                    280: .In mdoc.h ,
                    281: implemented in
                    282: .Pa mdoc.c .
1.3       kristaps  283: .It Fn mdoc_node
1.25      schwarze  284: Obtain the root node of a successful
                    285: .Xr mdoc
                    286: parse.
1.4       kristaps  287: This may only be used on a pointer returned by
                    288: .Fn mparse_result .
1.18      schwarze  289: Declared in
                    290: .In mdoc.h ,
                    291: implemented in
                    292: .Pa mdoc.c .
1.3       kristaps  293: .It Fn mparse_alloc
1.4       kristaps  294: Allocate a parser.
1.23      schwarze  295: The arguments have the following effect:
                    296: .Bl -tag -offset 5n -width inttype
1.25      schwarze  297: .It Ar options
                    298: When the
1.23      schwarze  299: .Dv MPARSE_MDOC
                    300: or
1.25      schwarze  301: .Dv MPARSE_MAN
                    302: bit is set, only that parser is used.
                    303: Otherwise, the document type is automatically detected.
                    304: .Pp
                    305: When the
                    306: .Dv MPARSE_SO
                    307: bit is set,
                    308: .Xr roff 7
                    309: .Ic \&so
                    310: file inclusion requests are always honoured.
                    311: Otherwise, if the request is the only content in an input file,
                    312: only the file name is remembered, to be returned in the
                    313: .Fa sodest
                    314: argument of
                    315: .Fn mparse_result .
                    316: .Pp
                    317: When the
                    318: .Dv MPARSE_QUICK
                    319: bit is set, parsing is aborted after the NAME section.
                    320: This is for example useful in
                    321: .Xr makewhatis 8
                    322: .Fl Q
                    323: to quickly build minimal databases.
1.23      schwarze  324: .It Ar wlevel
                    325: Can be set to
1.31      schwarze  326: .Dv MANDOCLEVEL_BADARG ,
1.23      schwarze  327: .Dv MANDOCLEVEL_ERROR ,
                    328: or
                    329: .Dv MANDOCLEVEL_WARNING .
                    330: Messages below the selected level will be suppressed.
                    331: .It Ar mmsg
                    332: A callback function to handle errors and warnings.
                    333: See
                    334: .Pa main.c
                    335: for an example.
                    336: .It Ar defos
                    337: A default string for the
                    338: .Xr mdoc 7
                    339: .Sq \&Os
                    340: macro, overriding the
                    341: .Dv OSNAME
                    342: preprocessor definition and the results of
                    343: .Xr uname 3 .
                    344: .El
                    345: .Pp
1.4       kristaps  346: The same parser may be used for multiple files so long as
                    347: .Fn mparse_reset
                    348: is called between parses.
                    349: .Fn mparse_free
                    350: must be called to free the memory allocated by this function.
1.18      schwarze  351: Declared in
                    352: .In mandoc.h ,
                    353: implemented in
                    354: .Pa read.c .
1.3       kristaps  355: .It Fn mparse_free
1.4       kristaps  356: Free all memory allocated by
                    357: .Fn mparse_alloc .
1.18      schwarze  358: Declared in
                    359: .In mandoc.h ,
                    360: implemented in
                    361: .Pa read.c .
1.14      kristaps  362: .It Fn mparse_getkeep
                    363: Acquire the keep buffer.
                    364: Must follow a call of
                    365: .Fn mparse_keep .
1.18      schwarze  366: Declared in
                    367: .In mandoc.h ,
                    368: implemented in
                    369: .Pa read.c .
1.14      kristaps  370: .It Fn mparse_keep
                    371: Instruct the parser to retain a copy of its parsed input.
                    372: This can be acquired with subsequent
                    373: .Fn mparse_getkeep
                    374: calls.
1.18      schwarze  375: Declared in
                    376: .In mandoc.h ,
                    377: implemented in
                    378: .Pa read.c .
1.26      schwarze  379: .It Fn mparse_open
1.32      schwarze  380: Open the file for reading.
                    381: If that fails and
1.26      schwarze  382: .Fa fname
1.32      schwarze  383: does not already end in
                    384: .Ql .gz ,
                    385: try again after appending
                    386: .Ql .gz .
                    387: Save the information whether the file is zipped or not.
1.26      schwarze  388: Return a file descriptor open for reading in
                    389: .Fa fd ,
                    390: or -1 on failure.
                    391: It can be passed to
                    392: .Fn mparse_readfd
                    393: or used directly.
                    394: Declared in
                    395: .In mandoc.h ,
                    396: implemented in
                    397: .Pa read.c .
1.3       kristaps  398: .It Fn mparse_readfd
1.30      schwarze  399: Parse a file descriptor opened with
                    400: .Xr open 2
                    401: or
1.29      schwarze  402: .Fn mparse_open .
1.30      schwarze  403: Pass the associated filename in
                    404: .Va fname .
1.29      schwarze  405: This function may be called multiple times with different parameters; however,
1.4       kristaps  406: .Fn mparse_reset
                    407: should be invoked between parses.
1.18      schwarze  408: Declared in
                    409: .In mandoc.h ,
                    410: implemented in
                    411: .Pa read.c .
1.3       kristaps  412: .It Fn mparse_reset
1.4       kristaps  413: Reset a parser so that
                    414: .Fn mparse_readfd
                    415: may be used again.
1.18      schwarze  416: Declared in
                    417: .In mandoc.h ,
                    418: implemented in
                    419: .Pa read.c .
1.3       kristaps  420: .It Fn mparse_result
1.4       kristaps  421: Obtain the result of a parse.
1.31      schwarze  422: One of the three pointers will be filled in.
1.18      schwarze  423: Declared in
                    424: .In mandoc.h ,
                    425: implemented in
                    426: .Pa read.c .
1.3       kristaps  427: .It Fn mparse_strerror
1.4       kristaps  428: Return a statically-allocated string representation of an error code.
1.18      schwarze  429: Declared in
                    430: .In mandoc.h ,
                    431: implemented in
                    432: .Pa read.c .
1.3       kristaps  433: .It Fn mparse_strlevel
1.4       kristaps  434: Return a statically-allocated string representation of a level code.
1.18      schwarze  435: Declared in
                    436: .In mandoc.h ,
                    437: implemented in
                    438: .Pa read.c .
1.3       kristaps  439: .El
                    440: .Ss Variables
                    441: .Bl -ohang
                    442: .It Va man_macronames
1.4       kristaps  443: The string representation of a man macro as indexed by
                    444: .Vt "enum mant" .
1.3       kristaps  445: .It Va mdoc_argnames
1.4       kristaps  446: The string representation of a mdoc macro argument as indexed by
                    447: .Vt "enum mdocargt" .
1.3       kristaps  448: .It Va mdoc_macronames
1.4       kristaps  449: The string representation of a mdoc macro as indexed by
                    450: .Vt "enum mdoct" .
1.1       kristaps  451: .El
                    452: .Sh IMPLEMENTATION NOTES
                    453: This section consists of structural documentation for
                    454: .Xr mdoc 7
                    455: and
                    456: .Xr man 7
1.11      kristaps  457: syntax trees and strings.
                    458: .Ss Man and Mdoc Strings
                    459: Strings may be extracted from mdoc and man meta-data, or from text
                    460: nodes (MDOC_TEXT and MAN_TEXT, respectively).
                    461: These strings have special non-printing formatting cues embedded in the
                    462: text itself, as well as
                    463: .Xr roff 7
                    464: escapes preserved from input.
                    465: Implementing systems will need to handle both situations to produce
                    466: human-readable text.
                    467: In general, strings may be assumed to consist of 7-bit ASCII characters.
                    468: .Pp
                    469: The following non-printing characters may be embedded in text strings:
                    470: .Bl -tag -width Ds
                    471: .It Dv ASCII_NBRSP
                    472: A non-breaking space character.
                    473: .It Dv ASCII_HYPH
                    474: A soft hyphen.
1.25      schwarze  475: .It Dv ASCII_BREAK
                    476: A breakable zero-width space.
1.11      kristaps  477: .El
                    478: .Pp
                    479: Escape characters are also passed verbatim into text strings.
                    480: An escape character is a sequence of characters beginning with the
                    481: backslash
                    482: .Pq Sq \e .
                    483: To construct human-readable text, these should be intercepted with
1.25      schwarze  484: .Xr mandoc_escape 3
                    485: and converted with one the functions described in
                    486: .Xr mchars_alloc 3 .
1.1       kristaps  487: .Ss Man Abstract Syntax Tree
                    488: This AST is governed by the ontological rules dictated in
                    489: .Xr man 7
                    490: and derives its terminology accordingly.
                    491: .Pp
                    492: The AST is composed of
                    493: .Vt struct man_node
                    494: nodes with element, root and text types as declared by the
                    495: .Va type
                    496: field.
                    497: Each node also provides its parse point (the
                    498: .Va line ,
                    499: .Va sec ,
                    500: and
                    501: .Va pos
                    502: fields), its position in the tree (the
                    503: .Va parent ,
                    504: .Va child ,
                    505: .Va next
                    506: and
                    507: .Va prev
                    508: fields) and some type-specific data.
                    509: .Pp
                    510: The tree itself is arranged according to the following normal form,
                    511: where capitalised non-terminals represent nodes.
                    512: .Pp
                    513: .Bl -tag -width "ELEMENTXX" -compact
                    514: .It ROOT
                    515: \(<- mnode+
                    516: .It mnode
                    517: \(<- ELEMENT | TEXT | BLOCK
                    518: .It BLOCK
                    519: \(<- HEAD BODY
                    520: .It HEAD
                    521: \(<- mnode*
                    522: .It BODY
                    523: \(<- mnode*
                    524: .It ELEMENT
                    525: \(<- ELEMENT | TEXT*
                    526: .It TEXT
1.11      kristaps  527: \(<- [[:ascii:]]*
1.1       kristaps  528: .El
                    529: .Pp
                    530: The only elements capable of nesting other elements are those with
1.25      schwarze  531: next-line scope as documented in
1.1       kristaps  532: .Xr man 7 .
                    533: .Ss Mdoc Abstract Syntax Tree
                    534: This AST is governed by the ontological
                    535: rules dictated in
                    536: .Xr mdoc 7
                    537: and derives its terminology accordingly.
                    538: .Qq In-line
                    539: elements described in
                    540: .Xr mdoc 7
                    541: are described simply as
                    542: .Qq elements .
                    543: .Pp
                    544: The AST is composed of
                    545: .Vt struct mdoc_node
                    546: nodes with block, head, body, element, root and text types as declared
                    547: by the
                    548: .Va type
                    549: field.
                    550: Each node also provides its parse point (the
                    551: .Va line ,
                    552: .Va sec ,
                    553: and
                    554: .Va pos
                    555: fields), its position in the tree (the
                    556: .Va parent ,
                    557: .Va child ,
                    558: .Va nchild ,
                    559: .Va next
                    560: and
                    561: .Va prev
                    562: fields) and some type-specific data, in particular, for nodes generated
                    563: from macros, the generating macro in the
                    564: .Va tok
                    565: field.
                    566: .Pp
                    567: The tree itself is arranged according to the following normal form,
                    568: where capitalised non-terminals represent nodes.
                    569: .Pp
                    570: .Bl -tag -width "ELEMENTXX" -compact
                    571: .It ROOT
                    572: \(<- mnode+
                    573: .It mnode
                    574: \(<- BLOCK | ELEMENT | TEXT
                    575: .It BLOCK
                    576: \(<- HEAD [TEXT] (BODY [TEXT])+ [TAIL [TEXT]]
                    577: .It ELEMENT
                    578: \(<- TEXT*
                    579: .It HEAD
                    580: \(<- mnode*
                    581: .It BODY
                    582: \(<- mnode* [ENDBODY mnode*]
                    583: .It TAIL
                    584: \(<- mnode*
                    585: .It TEXT
1.11      kristaps  586: \(<- [[:ascii:]]*
1.1       kristaps  587: .El
                    588: .Pp
                    589: Of note are the TEXT nodes following the HEAD, BODY and TAIL nodes of
                    590: the BLOCK production: these refer to punctuation marks.
                    591: Furthermore, although a TEXT node will generally have a non-zero-length
                    592: string, in the specific case of
                    593: .Sq \&.Bd \-literal ,
                    594: an empty line will produce a zero-length string.
                    595: Multiple body parts are only found in invocations of
                    596: .Sq \&Bl \-column ,
                    597: where a new body introduces a new phrase.
                    598: .Pp
                    599: The
                    600: .Xr mdoc 7
1.5       kristaps  601: syntax tree accommodates for broken block structures as well.
1.1       kristaps  602: The ENDBODY node is available to end the formatting associated
                    603: with a given block before the physical end of that block.
                    604: It has a non-null
                    605: .Va end
                    606: field, is of the BODY
                    607: .Va type ,
                    608: has the same
                    609: .Va tok
                    610: as the BLOCK it is ending, and has a
                    611: .Va pending
                    612: field pointing to that BLOCK's BODY node.
                    613: It is an indirect child of that BODY node
                    614: and has no children of its own.
                    615: .Pp
                    616: An ENDBODY node is generated when a block ends while one of its child
                    617: blocks is still open, like in the following example:
                    618: .Bd -literal -offset indent
                    619: \&.Ao ao
                    620: \&.Bo bo ac
                    621: \&.Ac bc
                    622: \&.Bc end
                    623: .Ed
                    624: .Pp
                    625: This example results in the following block structure:
                    626: .Bd -literal -offset indent
                    627: BLOCK Ao
                    628:     HEAD Ao
                    629:     BODY Ao
                    630:         TEXT ao
                    631:         BLOCK Bo, pending -> Ao
                    632:             HEAD Bo
                    633:             BODY Bo
                    634:                 TEXT bo
                    635:                 TEXT ac
                    636:                 ENDBODY Ao, pending -> Ao
                    637:                 TEXT bc
                    638: TEXT end
                    639: .Ed
                    640: .Pp
                    641: Here, the formatting of the
                    642: .Sq \&Ao
                    643: block extends from TEXT ao to TEXT ac,
                    644: while the formatting of the
                    645: .Sq \&Bo
                    646: block extends from TEXT bo to TEXT bc.
                    647: It renders as follows in
                    648: .Fl T Ns Cm ascii
                    649: mode:
                    650: .Pp
                    651: .Dl <ao [bo ac> bc] end
                    652: .Pp
                    653: Support for badly-nested blocks is only provided for backward
                    654: compatibility with some older
                    655: .Xr mdoc 7
                    656: implementations.
                    657: Using badly-nested blocks is
                    658: .Em strongly discouraged ;
                    659: for example, the
                    660: .Fl T Ns Cm html
                    661: and
                    662: .Fl T Ns Cm xhtml
                    663: front-ends to
                    664: .Xr mandoc 1
                    665: are unable to render them in any meaningful way.
                    666: Furthermore, behaviour when encountering badly-nested blocks is not
1.25      schwarze  667: consistent across troff implementations, especially when using multiple
1.1       kristaps  668: levels of badly-nested blocks.
                    669: .Sh SEE ALSO
                    670: .Xr mandoc 1 ,
1.25      schwarze  671: .Xr mandoc_escape 3 ,
                    672: .Xr mandoc_malloc 3 ,
                    673: .Xr mchars_alloc 3 ,
1.1       kristaps  674: .Xr eqn 7 ,
                    675: .Xr man 7 ,
1.6       kristaps  676: .Xr mandoc_char 7 ,
1.1       kristaps  677: .Xr mdoc 7 ,
                    678: .Xr roff 7 ,
                    679: .Xr tbl 7
                    680: .Sh AUTHORS
                    681: The
                    682: .Nm
                    683: library was written by
1.19      schwarze  684: .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .

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