diff options
Diffstat (limited to 'src/port/snprintf.c')
| -rw-r--r-- | src/port/snprintf.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/src/port/snprintf.c b/src/port/snprintf.c index 851e2ae330a..2c77eec1c6b 100644 --- a/src/port/snprintf.c +++ b/src/port/snprintf.c @@ -64,6 +64,14 @@ * * 5. Space and '#' flags are not implemented. * + * In addition, we support some extensions over C99: + * + * 1. Argument order control through "%n$" and "*n$", as required by POSIX. + * + * 2. "%m" expands to the value of strerror(errno), where errno is the + * value that variable had at the start of the call. This is a glibc + * extension, but a very useful one. + * * * Historically the result values of sprintf/snprintf varied across platforms. * This implementation now follows the C99 standard: @@ -155,6 +163,13 @@ static void flushbuffer(PrintfTarget *target); static void dopr(PrintfTarget *target, const char *format, va_list args); +/* + * Externally visible entry points. + * + * All of these are just wrappers around dopr(). Note it's essential that + * they not change the value of "errno" before reaching dopr(). + */ + int pg_vsnprintf(char *str, size_t count, const char *fmt, va_list args) { @@ -315,11 +330,12 @@ static void trailing_pad(int *padlen, PrintfTarget *target); /* - * dopr(): poor man's version of doprintf + * dopr(): the guts of *printf for all cases. */ static void dopr(PrintfTarget *target, const char *format, va_list args) { + int save_errno = errno; const char *format_start = format; int ch; bool have_dollar; @@ -497,6 +513,7 @@ nextch1: else have_non_dollar = true; break; + case 'm': case '%': break; } @@ -802,6 +819,15 @@ nextch2: precision, pointflag, target); break; + case 'm': + { + char errbuf[PG_STRERROR_R_BUFLEN]; + const char *errm = strerror_r(save_errno, + errbuf, sizeof(errbuf)); + + dostr(errm, strlen(errm), target); + } + break; case '%': dopr_outch('%', target); break; |