They're inextricably linked, not cross-referenced at all,
and not used anywhere else.
Now that they (realistically) exist to the reader, add a note
on how big nmatch can be; POSIX even says "The application developer
should note that there is probably no reason for using a value of
nmatch that is larger than preg−>re_nsub+1.".
Also remove the now-duplicate regmatch_t declaration.
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
man3/regex.3 | 54 +++++++++++++++++++++++++++++++++-------------------
1 file changed, 34 insertions(+), 20 deletions(-)
diff --git a/man3/regex.3 b/man3/regex.3
index 2b886eb77..2e9bb13ff 100644
--- a/man3/regex.3
+++ b/man3/regex.3
@@ -15,7 +15,7 @@ .SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
-.nf
+.EX
.B #include <regex.h>
.PP
.BI "int regcomp(regex_t *restrict " preg ", const char *restrict " regex ,
@@ -43,7 +43,7 @@ .SH SYNOPSIS
.B } regmatch_t;
.PP
.BR typedef " /* ... */ " regoff_t;
-.fi
+.EE
.SH DESCRIPTION
.SS Compilation
.BR regcomp ()
@@ -60,6 +60,21 @@ .SS Compilation
The locale must be the same when running
.BR regexec ().
.PP
+After
+.BR regcomp ()
+succeeds,
+.I preg->re_nsub
+holds the number of subexpressions in
+.IR regex .
+Thus, a value of
+.I preg->re_nsub
++ 1
+passed as
+.I nmatch
+to
+.BR regexec ()
+is sufficient to capture all matches.
+.PP
.I cflags
is the
bitwise OR
@@ -192,22 +207,6 @@ .SS Match offsets
.IR N+1 .)
Any unused structure elements will contain the value \-1.
.PP
-The
-.I regmatch_t
-structure which is the type of
-.I pmatch
-is defined in
-.IR <regex.h> .
-.PP
-.in +4n
-.EX
-typedef struct {
- regoff_t rm_so;
- regoff_t rm_eo;
-} regmatch_t;
-.EE
-.in
-.PP
Each
.I rm_so
element that is not \-1 indicates the start offset of the next largest
@@ -218,7 +217,7 @@ .SS Match offsets
which is the offset of the first character after the matching text.
.PP
.I regoff_t
-It is a signed integer type
+is a signed integer type
capable of storing the largest value that can be stored in either an
.I ptrdiff_t
type or a
@@ -342,12 +341,27 @@ .SH HISTORY
POSIX.1-2001.
.PP
Prior to POSIX.1-2008,
-the type was
+.I regoff_t
+was required to be
capable of storing the largest value that can be stored in either an
.I off_t
type or a
.I ssize_t
type.
+.SH NOTES
+.I re_nsub
+is only required to be initialized if
+.B REG_NOSUB
+wasn't specified, but all known implementations initialize it regardless.
+.\" glibc, musl, 4.4BSD, illumos
+.PP
+Both
+.I regex_t
+and
+.I regmatch_t
+may (and do) have more members, in any order.
+Always reference them by name.
+.\" illumos has two more start/end pairs and the first one is of pointers
.SH EXAMPLES
.EX
#include <stdint.h>
--
2.30.2
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