system_data_types.7: Add intN_t family of types

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/system_data_types.7

@@ -380,6 +380,85 @@ See also the
 .I uintmax_t
 type in this page.
 .RE
+.\"------------------------------------- intN_t -----------------------/
+.TP
+.IR int N _t
+.RS
+.br
+Include:
+.IR <stdint.h> .
+Alternatively,
+.IR <inttypes.h> .
+.PP
+.IR int8_t ", " int16_t ", " int32_t ", " int64_t
+.PP
+A signed integer type
+of a fixed width of exactly N bits,
+N being the value specified in its type name.
+According to the C language standard, they shall be
+capable of storing values in the range
+.RB [ INT N _MIN ,
+.BR INT N _MAX ],
+substituting N by the appropriate number.
+.PP
+According to POSIX,
+.IR int8_t ", " int16_t
+and
+.I int32_t
+are required;
+.I int64_t
+is only required in implementations that provide integer types
+with width 64;
+and all other types of this form are optional.
+.PP
+The length modifiers for the
+.IR int N _t
+types for the
+.BR printf (3)
+family of functions
+are expanded by macros of the forms
+.BR PRId N
+and
+.BR PRIi N
+(defined in
+.IR <inttypes.h> );
+resulting for example in
+.B %"PRId64"
+or
+.B %"PRIi64"
+for printing
+.I int64_t
+values.
+The length modifiers for the
+.IR int N _t
+types for the
+.BR scanf (3)
+family of functions
+are expanded by macros of the forms
+.BR SCNd N
+and
+.BR SCNi N,
+(defined in
+.IR <inttypes.h> );
+resulting for example in
+.B %"SCNd8"
+or
+.B %"SCNi8"
+for scanning
+.I int8_t
+values.
+.PP
+Conforming to: C99 and later; POSIX.1-2001 and later.
+.PP
+See also the
+.IR __int128 ,
+.IR intmax_t ,
+.IR uint N _t ,
+.I uintmax_t
+and
+.I unsigned __int128
+types in this page.
+.RE
 .\"------------------------------------- lconv ------------------------/
 .TP
 .I lconv