Author: kib
Date: Tue May 22 11:05:40 2018
New Revision: 334031
URL: https://svnweb.freebsd.org/changeset/base/334031
Log:
Implement printf(3) family %m format string extension.
Reviewed by: ed, dim (code only)
Sponsored by: Mellanox Technologies
MFC after: 1 week
Modified:
head/lib/libc/stdio/printf.3
head/lib/libc/stdio/vfprintf.c
Modified: head/lib/libc/stdio/printf.3
==============================================================================
--- head/lib/libc/stdio/printf.3 Tue May 22 10:31:06 2018
(r334030)
+++ head/lib/libc/stdio/printf.3 Tue May 22 11:05:40 2018
(r334031)
@@ -32,7 +32,7 @@
.\" @(#)printf.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
-.Dd July 30, 2016
+.Dd May 22, 2018
.Dt PRINTF 3
.Os
.Sh NAME
@@ -651,6 +651,12 @@ integer indicated by the
.Vt "int *"
(or variant) pointer argument.
No argument is converted.
+.It Cm m
+Print the string representation of the error code stored in the
+.Dv errno
+variable at the beginning of the call, as returned by
+.Xr strerror 3 .
+No argument is taken.
.It Cm %
A
.Ql %
@@ -730,6 +736,12 @@ and
.Cm \&%U
are not standard and
are provided only for backward compatibility.
+The conversion format
+.Cm \&%m
+is also not standard and provides the popular extension from the
+.Tn GNU C
+library.
+.Pp
The effect of padding the
.Cm %p
format with zeros (either by the
@@ -767,9 +779,11 @@ or the return value would be too large to be represent
.El
.Sh SEE ALSO
.Xr printf 1 ,
+.Xr errno 2 ,
.Xr fmtcheck 3 ,
.Xr scanf 3 ,
.Xr setlocale 3 ,
+.Xr strerror 3 ,
.Xr wprintf 3
.Sh STANDARDS
Subject to the caveats noted in the
@@ -822,6 +836,12 @@ and
.Fn vdprintf
functions were added in
.Fx 8.0 .
+The
+.Cm \&%m
+format extension first appeared in the
+.Tn GNU C
+library, and was implemented in
+.Fx 12.0 .
.Sh BUGS
The
.Nm
Modified: head/lib/libc/stdio/vfprintf.c
==============================================================================
--- head/lib/libc/stdio/vfprintf.c Tue May 22 10:31:06 2018
(r334030)
+++ head/lib/libc/stdio/vfprintf.c Tue May 22 11:05:40 2018
(r334031)
@@ -317,6 +317,7 @@ __vfprintf(FILE *fp, locale_t locale, const char *fmt0
int ret; /* return value accumulator */
int width; /* width from format (%8d), or 0 */
int prec; /* precision from format; <0 for N/A */
+ int saved_errno;
char sign; /* sign prefix (' ', '+', '-', or \0) */
struct grouping_state gs; /* thousands' grouping info */
@@ -466,6 +467,7 @@ __vfprintf(FILE *fp, locale_t locale, const char *fmt0
savserr = fp->_flags & __SERR;
fp->_flags &= ~__SERR;
+ saved_errno = errno;
convbuf = NULL;
fmt = (char *)fmt0;
argtable = NULL;
@@ -776,6 +778,11 @@ fp_common:
}
break;
#endif /* !NO_FLOATING_POINT */
+ case 'm':
+ cp = strerror(saved_errno);
+ size = (prec >= 0) ? strnlen(cp, prec) : strlen(cp);
+ sign = '\0';
+ break;
case 'n':
/*
* Assignment-like behavior is specified if the
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