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Implement %m in src/port/snprintf.c, and teach elog.c to rely on that.

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I started out with the idea that we needed to detect use of %m format specs
in contexts other than elog/ereport calls, because we couldn't rely on that
working in *printf calls.  But a better answer is to fix things so that it
does work.  Now that we're using snprintf.c all the time, we can implement
%m in that and we've fixed the problem.

This requires also adjusting our various printf-wrapping functions so that
they ensure "errno" is preserved when they call snprintf.c.

Remove elog.c's handmade implementation of %m, and let it rely on
snprintf to support the feature.  That should provide some performance
gain, though I've not attempted to measure it.

There are a lot of places where we could now simplify 'printf("%s",
strerror(errno))' into 'printf("%m")', but I'm not in any big hurry
to make that happen.

Patch by me, reviewed by Michael Paquier

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2018-09-26 13:31:56 -04:00
parent 96bf88d527
commit d6c55de1f9
8 changed files with 57 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/lib/stringinfo.c
View File

@@ -77,12 +77,15 @@ resetStringInfo(StringInfo str)
void
appendStringInfo(StringInfo str, const char *fmt,...)
{
int save_errno = errno;
for (;;)
{
va_list args;
int needed;
/* Try to format the data. */
errno = save_errno;
va_start(args, fmt);
needed = appendStringInfoVA(str, fmt, args);
va_end(args);
@@ -105,6 +108,9 @@ appendStringInfo(StringInfo str, const char *fmt,...)
* pass the return value to enlargeStringInfo() before trying again; see
* appendStringInfo for standard usage pattern.
*
* Caution: callers must be sure to preserve their entry-time errno
* when looping, in case the fmt contains "%m".
*
* XXX This API is ugly, but there seems no alternative given the C spec's
* restrictions on what can portably be done with va_list arguments: you have
* to redo va_start before you can rescan the argument list, and we can't do

70
src/backend/utils/error/elog.c
View File

@@ -177,7 +177,6 @@ static void write_csvlog(ErrorData *edata);
static void send_message_to_server_log(ErrorData *edata);
static void write_pipe_chunks(char *data, int len, int dest);
static void send_message_to_frontend(ErrorData *edata);
static char *expand_fmt_string(const char *fmt, ErrorData *edata);
static const char *error_severity(int elevel);
static void append_with_tabs(StringInfo buf, const char *str);
static bool is_log_level_output(int elevel, int log_min_level);
@@ -705,13 +704,10 @@ errcode_for_socket_access(void)
*/
#define EVALUATE_MESSAGE(domain, targetfield, appendval, translateit) \
{ \
char *fmtbuf; \
StringInfoData buf; \
/* Internationalize the error format string */ \
if ((translateit) && !in_error_recursion_trouble()) \
fmt = dgettext((domain), fmt); \
/* Expand %m in format string */ \
fmtbuf = expand_fmt_string(fmt, edata); \
initStringInfo(&buf); \
if ((appendval) && edata->targetfield) { \
appendStringInfoString(&buf, edata->targetfield); \
@@ -722,15 +718,14 @@ errcode_for_socket_access(void)
{ \
va_list args; \
int needed; \
errno = edata->saved_errno; \
va_start(args, fmt); \
needed = appendStringInfoVA(&buf, fmtbuf, args); \
needed = appendStringInfoVA(&buf, fmt, args); \
va_end(args); \
if (needed == 0) \
break; \
enlargeStringInfo(&buf, needed); \
} \
/* Done with expanded fmt */ \
pfree(fmtbuf); \
/* Save the completed message into the stack item */ \
if (edata->targetfield) \
pfree(edata->targetfield); \
@@ -746,15 +741,12 @@ errcode_for_socket_access(void)
#define EVALUATE_MESSAGE_PLURAL(domain, targetfield, appendval) \
{ \
const char *fmt; \
char *fmtbuf; \
StringInfoData buf; \
/* Internationalize the error format string */ \
if (!in_error_recursion_trouble()) \
fmt = dngettext((domain), fmt_singular, fmt_plural, n); \
else \
fmt = (n == 1 ? fmt_singular : fmt_plural); \
/* Expand %m in format string */ \
fmtbuf = expand_fmt_string(fmt, edata); \
initStringInfo(&buf); \
if ((appendval) && edata->targetfield) { \
appendStringInfoString(&buf, edata->targetfield); \
@@ -765,15 +757,14 @@ errcode_for_socket_access(void)
{ \
va_list args; \
int needed; \
errno = edata->saved_errno; \
va_start(args, n); \
needed = appendStringInfoVA(&buf, fmtbuf, args); \
needed = appendStringInfoVA(&buf, fmt, args); \
va_end(args); \
if (needed == 0) \
break; \
enlargeStringInfo(&buf, needed); \
} \
/* Done with expanded fmt */ \
pfree(fmtbuf); \
/* Save the completed message into the stack item */ \
if (edata->targetfield) \
pfree(edata->targetfield); \
@@ -3328,59 +3319,6 @@ send_message_to_frontend(ErrorData *edata)
*/
/*
* expand_fmt_string --- process special format codes in a format string
*
* We must replace %m with the appropriate strerror string, since vsnprintf
* won't know what to do with it.
*
* The result is a palloc'd string.
*/
static char *
expand_fmt_string(const char *fmt, ErrorData *edata)
{
StringInfoData buf;
const char *cp;
initStringInfo(&buf);
for (cp = fmt; *cp; cp++)
{
if (cp[0] == '%' && cp[1] != '\0')
{
cp++;
if (*cp == 'm')
{
/*
* Replace %m by system error string. If there are any %'s in
* the string, we'd better double them so that vsnprintf won't
* misinterpret.
*/
const char *cp2;
cp2 = strerror(edata->saved_errno);
for (; *cp2; cp2++)
{
if (*cp2 == '%')
appendStringInfoCharMacro(&buf, '%');
appendStringInfoCharMacro(&buf, *cp2);
}
}
else
{
/* copy % and next char --- this avoids trouble with %%m */
appendStringInfoCharMacro(&buf, '%');
appendStringInfoCharMacro(&buf, *cp);
}
}
else
appendStringInfoCharMacro(&buf, *cp);
}
return buf.data;
}
/*
* error_severity --- get string representing elevel
*