elog.c

/*-------------------------------------------------------------------------
 *
 * elog.c
 *	  error logging and reporting
 *
 * Some notes about recursion and errors during error processing:
 *
 * We need to be robust about recursive-error scenarios --- for example,
 * if we run out of memory, it's important to be able to report that fact.
 * There are a number of considerations that go into this.
 *
 * First, distinguish between re-entrant use and actual recursion.	It
 * is possible for an error or warning message to be emitted while the
 * parameters for an error message are being computed.	In this case
 * errstart has been called for the outer message, and some field values
 * may have already been saved, but we are not actually recursing.	We handle
 * this by providing a (small) stack of ErrorData records.	The inner message
 * can be computed and sent without disturbing the state of the outer message.
 * (If the inner message is actually an error, this isn't very interesting
 * because control won't come back to the outer message generator ... but
 * if the inner message is only debug or log data, this is critical.)
 *
 * Second, actual recursion will occur if an error is reported by one of
 * the elog.c routines or something they call.	By far the most probable
 * scenario of this sort is "out of memory"; and it's also the nastiest
 * to handle because we'd likely also run out of memory while trying to
 * report this error!  Our escape hatch for this condition is to force any
 * such messages up to ERROR level if they aren't already (so that we will
 * not need to return to the outer elog.c call), and to reset the ErrorContext
 * to empty before trying to process the inner message.  Since ErrorContext
 * is guaranteed to have at least 8K of space in it (see mcxt.c), we should
 * be able to process an "out of memory" message successfully.
 *
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/error/elog.c,v 1.145 2004/08/04 20:58:46 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <signal.h>
#include <ctype.h>
#ifdef HAVE_SYSLOG
#include <syslog.h>
#endif

#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "postmaster/postmaster.h"
#include "storage/ipc.h"
#include "tcop/tcopprot.h"
#include "utils/memutils.h"
#include "utils/guc.h"


/* Global variables */
ErrorContextCallback *error_context_stack = NULL;

sigjmp_buf *PG_exception_stack = NULL;

/* GUC parameters */
PGErrorVerbosity Log_error_verbosity = PGERROR_VERBOSE;
char       *Log_line_prefix = NULL; /* format for extra log line info */
unsigned int Log_destination = LOG_DESTINATION_STDERR;

#ifdef HAVE_SYSLOG
char	   *Syslog_facility;	/* openlog() parameters */
char	   *Syslog_ident;

static void write_syslog(int level, const char *line);
#endif
#ifdef WIN32
static void write_eventlog(int level, const char *line);
#endif

/* We provide a small stack of ErrorData records for re-entrant cases */
#define ERRORDATA_STACK_SIZE  5

static ErrorData errordata[ERRORDATA_STACK_SIZE];

static int	errordata_stack_depth = -1; /* index of topmost active frame */

static int	recursion_depth = 0;	/* to detect actual recursion */


/* Macro for checking errordata_stack_depth is reasonable */
#define CHECK_STACK_DEPTH() \
	do { \
		if (errordata_stack_depth < 0) \
		{ \
			errordata_stack_depth = -1; \
			ereport(ERROR, (errmsg_internal("errstart was not called"))); \
		} \
	} while (0)


static void log_line_prefix(StringInfo buf);
static void send_message_to_server_log(ErrorData *edata);
static void send_message_to_frontend(ErrorData *edata);
static char *expand_fmt_string(const char *fmt, ErrorData *edata);
static const char *useful_strerror(int errnum);
static const char *error_severity(int elevel);
static void append_with_tabs(StringInfo buf, const char *str);


/*
 * errstart --- begin an error-reporting cycle
 *
 * Create a stack entry and store the given parameters in it.  Subsequently,
 * errmsg() and perhaps other routines will be called to further populate
 * the stack entry.  Finally, errfinish() will be called to actually process
 * the error report.
 *
 * Returns TRUE in normal case.  Returns FALSE to short-circuit the error
 * report (if it's a warning or lower and not to be reported anywhere).
 */
bool
errstart(int elevel, const char *filename, int lineno,
		 const char *funcname)
{
	ErrorData  *edata;
	bool		output_to_server = false;
	bool		output_to_client = false;

	/*
	 * First decide whether we need to process this report at all; if it's
	 * warning or less and not enabled for logging, just return FALSE
	 * without starting up any error logging machinery.
	 */

	/*
	 * Convert initialization errors into fatal errors. This is probably
	 * redundant, because PG_exception_stack will still be null anyway.
	 */
	if (elevel == ERROR && IsInitProcessingMode())
		elevel = FATAL;

	/*
	 * If we are inside a critical section, all errors become PANIC
	 * errors.	See miscadmin.h.
	 */
	if (elevel >= ERROR)
	{
		if (CritSectionCount > 0)
			elevel = PANIC;
	}

	/* Determine whether message is enabled for server log output */
	if (IsPostmasterEnvironment)
	{
		/* Complicated because LOG is sorted out-of-order for this purpose */
		if (elevel == LOG || elevel == COMMERROR)
		{
			if (log_min_messages == LOG)
				output_to_server = true;
			else if (log_min_messages < FATAL)
				output_to_server = true;
		}
		else
		{
			/* elevel != LOG */
			if (log_min_messages == LOG)
			{
				if (elevel >= FATAL)
					output_to_server = true;
			}
			/* Neither is LOG */
			else if (elevel >= log_min_messages)
				output_to_server = true;
		}
	}
	else
	{
		/* In bootstrap/standalone case, do not sort LOG out-of-order */
		output_to_server = (elevel >= log_min_messages);
	}

	/* Determine whether message is enabled for client output */
	if (whereToSendOutput == Remote && elevel != COMMERROR)
	{
		/*
		 * client_min_messages is honored only after we complete the
		 * authentication handshake.  This is required both for security
		 * reasons and because many clients can't handle NOTICE messages
		 * during authentication.
		 */
		if (ClientAuthInProgress)
			output_to_client = (elevel >= ERROR);
		else
			output_to_client = (elevel >= client_min_messages ||
								elevel == INFO);
	}

	/* Skip processing effort if non-error message will not be output */
	if (elevel < ERROR && !output_to_server && !output_to_client)
		return false;

	/*
	 * Okay, crank up a stack entry to store the info in.
	 */

	if (recursion_depth++ > 0)
	{
		/*
		 * Ooops, error during error processing.  Clear ErrorContext and
		 * force level up to ERROR or greater, as discussed at top of
		 * file.  Adjust output decisions too.
		 */
		MemoryContextReset(ErrorContext);
		output_to_server = true;
		if (whereToSendOutput == Remote && elevel != COMMERROR)
			output_to_client = true;
		elevel = Max(elevel, ERROR);

		/*
		 * If we recurse more than once, the problem might be something
		 * broken in a context traceback routine.  Abandon them too.
		 */
		if (recursion_depth > 2)
			error_context_stack = NULL;
	}
	if (++errordata_stack_depth >= ERRORDATA_STACK_SIZE)
	{
		/*
		 * Wups, stack not big enough.  We treat this as a PANIC condition
		 * because it suggests an infinite loop of errors during error
		 * recovery.
		 */
		errordata_stack_depth = -1;	/* make room on stack */
		ereport(PANIC, (errmsg_internal("ERRORDATA_STACK_SIZE exceeded")));
	}

	/* Initialize data for this error frame */
	edata = &errordata[errordata_stack_depth];
	MemSet(edata, 0, sizeof(ErrorData));
	edata->elevel = elevel;
	edata->output_to_server = output_to_server;
	edata->output_to_client = output_to_client;
	edata->filename = filename;
	edata->lineno = lineno;
	edata->funcname = funcname;
	/* Select default errcode based on elevel */
	if (elevel >= ERROR)
		edata->sqlerrcode = ERRCODE_INTERNAL_ERROR;
	else if (elevel == WARNING)
		edata->sqlerrcode = ERRCODE_WARNING;
	else
		edata->sqlerrcode = ERRCODE_SUCCESSFUL_COMPLETION;
	/* errno is saved here so that error parameter eval can't change it */
	edata->saved_errno = errno;

	recursion_depth--;
	return true;
}

/*
 * errfinish --- end an error-reporting cycle
 *
 * Produce the appropriate error report(s) and pop the error stack.
 *
 * If elevel is ERROR or worse, control does not return to the caller.
 * See elog.h for the error level definitions.
 */
void
errfinish(int dummy,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	int			elevel = edata->elevel;
	MemoryContext oldcontext;
	ErrorContextCallback *econtext;

	recursion_depth++;
	CHECK_STACK_DEPTH();

	/*
	 * Do processing in ErrorContext, which we hope has enough reserved
	 * space to report an error.
	 */
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	/*
	 * Call any context callback functions.  Errors occurring in callback
	 * functions will be treated as recursive errors --- this ensures we
	 * will avoid infinite recursion (see errstart).
	 */
	for (econtext = error_context_stack;
		 econtext != NULL;
		 econtext = econtext->previous)
		(*econtext->callback) (econtext->arg);

	/*
	 * If the error level is ERROR or more, we are not going to return to
	 * caller; therefore, if there is any stacked error already in
	 * progress it will be lost.  This is more or less okay, except we do
	 * not want to have a FATAL or PANIC error downgraded because the
	 * reporting process was interrupted by a lower-grade error.  So check
	 * the stack and make sure we panic if panic is warranted.
	 */
	if (elevel >= ERROR)
	{
		int			i;

		for (i = 0; i <= errordata_stack_depth; i++)
			elevel = Max(elevel, errordata[i].elevel);
	}

	/*
	 * Check some other reasons for treating ERROR as FATAL:
	 *
	 * 1. we have no handler to pass the error to (implies we are in
	 * the postmaster or in backend startup).
	 *
	 * 2. ExitOnAnyError mode switch is set (initdb uses this).
	 *
	 * 3. the error occurred after proc_exit has begun to run.	(It's
	 * proc_exit's responsibility to see that this doesn't turn into
	 * infinite recursion!)
	 */
	if (elevel == ERROR)
	{
		if (PG_exception_stack == NULL ||
			ExitOnAnyError ||
			proc_exit_inprogress)
			elevel = FATAL;
		else
		{
			/*
			 * Otherwise we can pass the error off to the current handler.
			 * Printing it and popping the stack is the responsibility of
			 * the handler.
			 *
			 * We do some minimal cleanup before longjmp'ing so that handlers
			 * can execute in a reasonably sane state.
			 */

			/* This is just in case the error came while waiting for input */
			ImmediateInterruptOK = false;

			/*
			 * Reset InterruptHoldoffCount in case we ereport'd from inside an
			 * interrupt holdoff section.  (We assume here that no handler
			 * will itself be inside a holdoff section.  If necessary, such
			 * a handler could save and restore InterruptHoldoffCount for
			 * itself, but this should make life easier for most.)
			 */
			InterruptHoldoffCount = 0;

			CritSectionCount = 0;	/* should be unnecessary, but... */

			/*
			 * Note that we leave CurrentMemoryContext set to ErrorContext.
			 * The handler should reset it to something else soon.
			 */

			recursion_depth--;
			PG_RE_THROW();
		}
	}

	/*
	 * If we are doing FATAL or PANIC, abort any old-style COPY OUT in
	 * progress, so that we can report the message before dying.  (Without
	 * this, pq_putmessage will refuse to send the message at all, which
	 * is what we want for NOTICE messages, but not for fatal exits.)
	 * This hack is necessary because of poor design of old-style copy
	 * protocol.  Note we must do this even if client is fool enough to
	 * have set client_min_messages above FATAL, so don't look at
	 * output_to_client.
	 */
	if (elevel >= FATAL && whereToSendOutput == Remote)
		pq_endcopyout(true);

	/* Emit the message to the right places */
	EmitErrorReport();

	/* Now free up subsidiary data attached to stack entry, and release it */
	if (edata->message)
		pfree(edata->message);
	if (edata->detail)
		pfree(edata->detail);
	if (edata->hint)
		pfree(edata->hint);
	if (edata->context)
		pfree(edata->context);
	if (edata->internalquery)
		pfree(edata->internalquery);

	errordata_stack_depth--;

	/* Exit error-handling context */
	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;

	/*
	 * Perform error recovery action as specified by elevel.
	 */
	if (elevel == FATAL)
	{
		/*
		 * For a FATAL error, we let proc_exit clean up and exit.
		 */
		ImmediateInterruptOK = false;

		/*
		 * If we just reported a startup failure, the client will
		 * disconnect on receiving it, so don't send any more to the
		 * client.
		 */
		if (PG_exception_stack == NULL && whereToSendOutput == Remote)
			whereToSendOutput = None;

		/*
		 * fflush here is just to improve the odds that we get to see
		 * the error message, in case things are so hosed that
		 * proc_exit crashes.  Any other code you might be tempted to
		 * add here should probably be in an on_proc_exit callback
		 * instead.
		 */
		fflush(stdout);
		fflush(stderr);

		/*
		 * If proc_exit is already running, we exit with nonzero exit code to
		 * indicate that something's pretty wrong.  We also want to exit with
		 * nonzero exit code if not running under the postmaster (for example,
		 * if we are being run from the initdb script, we'd better return an
		 * error status).
		 */
		proc_exit(proc_exit_inprogress || !IsUnderPostmaster);
	}

	if (elevel >= PANIC)
	{
		/*
		 * Serious crash time. Postmaster will observe nonzero process
		 * exit status and kill the other backends too.
		 *
		 * XXX: what if we are *in* the postmaster?  abort() won't kill our
		 * children...
		 */
		ImmediateInterruptOK = false;
		fflush(stdout);
		fflush(stderr);
		abort();
	}

	/* We reach here if elevel <= WARNING. OK to return to caller. */
}


/*
 * errcode --- add SQLSTATE error code to the current error
 *
 * The code is expected to be represented as per MAKE_SQLSTATE().
 */
int
errcode(int sqlerrcode)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	edata->sqlerrcode = sqlerrcode;

	return 0;					/* return value does not matter */
}


/*
 * errcode_for_file_access --- add SQLSTATE error code to the current error
 *
 * The SQLSTATE code is chosen based on the saved errno value.	We assume
 * that the failing operation was some type of disk file access.
 *
 * NOTE: the primary error message string should generally include %m
 * when this is used.
 */
int
errcode_for_file_access(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	switch (edata->saved_errno)
	{
			/* Permission-denied failures */
		case EPERM:				/* Not super-user */
		case EACCES:			/* Permission denied */
#ifdef EROFS
		case EROFS:				/* Read only file system */
#endif
			edata->sqlerrcode = ERRCODE_INSUFFICIENT_PRIVILEGE;
			break;

			/* File not found */
		case ENOENT:			/* No such file or directory */
			edata->sqlerrcode = ERRCODE_UNDEFINED_FILE;
			break;

			/* Duplicate file */
		case EEXIST:			/* File exists */
			edata->sqlerrcode = ERRCODE_DUPLICATE_FILE;
			break;

			/* Wrong object type or state */
		case ENOTDIR:			/* Not a directory */
		case EISDIR:			/* Is a directory */
#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST)	/* same code on AIX */
		case ENOTEMPTY:			/* Directory not empty */
#endif
			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
			break;

			/* Insufficient resources */
		case ENOSPC:			/* No space left on device */
			edata->sqlerrcode = ERRCODE_DISK_FULL;
			break;

		case ENFILE:			/* File table overflow */
		case EMFILE:			/* Too many open files */
			edata->sqlerrcode = ERRCODE_INSUFFICIENT_RESOURCES;
			break;

			/* Hardware failure */
		case EIO:				/* I/O error */
			edata->sqlerrcode = ERRCODE_IO_ERROR;
			break;

			/* All else is classified as internal errors */
		default:
			edata->sqlerrcode = ERRCODE_INTERNAL_ERROR;
			break;
	}

	return 0;					/* return value does not matter */
}

/*
 * errcode_for_socket_access --- add SQLSTATE error code to the current error
 *
 * The SQLSTATE code is chosen based on the saved errno value.	We assume
 * that the failing operation was some type of socket access.
 *
 * NOTE: the primary error message string should generally include %m
 * when this is used.
 */
int
errcode_for_socket_access(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	switch (edata->saved_errno)
	{
			/* Loss of connection */
		case EPIPE:
#ifdef ECONNRESET
		case ECONNRESET:
#endif
			edata->sqlerrcode = ERRCODE_CONNECTION_FAILURE;
			break;

			/* All else is classified as internal errors */
		default:
			edata->sqlerrcode = ERRCODE_INTERNAL_ERROR;
			break;
	}

	return 0;					/* return value does not matter */
}


/*
 * This macro handles expansion of a format string and associated parameters;
 * it's common code for errmsg(), errdetail(), etc.  Must be called inside
 * a routine that is declared like "const char *fmt, ..." and has an edata
 * pointer set up.	The message is assigned to edata->targetfield, or
 * appended to it if appendval is true.
 *
 * Note: we pstrdup the buffer rather than just transferring its storage
 * to the edata field because the buffer might be considerably larger than
 * really necessary.
 */
#define EVALUATE_MESSAGE(targetfield, appendval)  \
	{ \
		char		   *fmtbuf; \
		StringInfoData	buf; \
		/* Internationalize the error format string */ \
		fmt = gettext(fmt); \
		/* Expand %m in format string */ \
		fmtbuf = expand_fmt_string(fmt, edata); \
		initStringInfo(&buf); \
		if ((appendval) && edata->targetfield) \
			appendStringInfo(&buf, "%s\n", edata->targetfield); \
		/* Generate actual output --- have to use appendStringInfoVA */ \
		for (;;) \
		{ \
			va_list		args; \
			bool		success; \
			va_start(args, fmt); \
			success = appendStringInfoVA(&buf, fmtbuf, args); \
			va_end(args); \
			if (success) \
				break; \
			enlargeStringInfo(&buf, buf.maxlen); \
		} \
		/* Done with expanded fmt */ \
		pfree(fmtbuf); \
		/* Save the completed message into the stack item */ \
		if (edata->targetfield) \
			pfree(edata->targetfield); \
		edata->targetfield = pstrdup(buf.data); \
		pfree(buf.data); \
	}


/*
 * errmsg --- add a primary error message text to the current error
 *
 * In addition to the usual %-escapes recognized by printf, "%m" in
 * fmt is replaced by the error message for the caller's value of errno.
 *
 * Note: no newline is needed at the end of the fmt string, since
 * ereport will provide one for the output methods that need it.
 */
int
errmsg(const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(message, false);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
	return 0;					/* return value does not matter */
}


/*
 * errmsg_internal --- add a primary error message text to the current error
 *
 * This is exactly like errmsg() except that strings passed to errmsg_internal
 * are customarily left out of the internationalization message dictionary.
 * This should be used for "can't happen" cases that are probably not worth
 * spending translation effort on.
 */
int
errmsg_internal(const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(message, false);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
	return 0;					/* return value does not matter */
}


/*
 * errdetail --- add a detail error message text to the current error
 */
int
errdetail(const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(detail, false);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
	return 0;					/* return value does not matter */
}


/*
 * errhint --- add a hint error message text to the current error
 */
int
errhint(const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(hint, false);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
	return 0;					/* return value does not matter */
}


/*
 * errcontext --- add a context error message text to the current error
 *
 * Unlike other cases, multiple calls are allowed to build up a stack of
 * context information.  We assume earlier calls represent more-closely-nested
 * states.
 */
int
errcontext(const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(context, true);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
	return 0;					/* return value does not matter */
}


/*
 * errfunction --- add reporting function name to the current error
 *
 * This is used when backwards compatibility demands that the function
 * name appear in messages sent to old-protocol clients.  Note that the
 * passed string is expected to be a non-freeable constant string.
 */
int
errfunction(const char *funcname)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	edata->funcname = funcname;
	edata->show_funcname = true;

	return 0;					/* return value does not matter */
}

/*
 * errposition --- add cursor position to the current error
 */
int
errposition(int cursorpos)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	edata->cursorpos = cursorpos;

	return 0;					/* return value does not matter */
}

/*
 * internalerrposition --- add internal cursor position to the current error
 */
int
internalerrposition(int cursorpos)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	edata->internalpos = cursorpos;

	return 0;					/* return value does not matter */
}

/*
 * internalerrquery --- add internal query text to the current error
 *
 * Can also pass NULL to drop the internal query text entry.  This case
 * is intended for use in error callback subroutines that are editorializing
 * on the layout of the error report.
 */
int
internalerrquery(const char *query)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	if (edata->internalquery)
	{
		pfree(edata->internalquery);
		edata->internalquery = NULL;
	}

	if (query)
		edata->internalquery = MemoryContextStrdup(ErrorContext, query);

	return 0;					/* return value does not matter */
}

/*
 * geterrposition --- return the currently set error position (0 if none)
 *
 * This is only intended for use in error callback subroutines, since there
 * is no other place outside elog.c where the concept is meaningful.
 */
int
geterrposition(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	return edata->cursorpos;
}

/*
 * getinternalerrposition --- same for internal error position
 *
 * This is only intended for use in error callback subroutines, since there
 * is no other place outside elog.c where the concept is meaningful.
 */
int
getinternalerrposition(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];

	/* we don't bother incrementing recursion_depth */
	CHECK_STACK_DEPTH();

	return edata->internalpos;
}


/*
 * elog_finish --- finish up for old-style API
 *
 * The elog() macro already called errstart, but with ERROR rather than
 * the true elevel.
 */
void
elog_finish(int elevel, const char *fmt,...)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	CHECK_STACK_DEPTH();

	/*
	 * We need to redo errstart() because the elog macro had to call it
	 * with bogus elevel.
	 */
	errordata_stack_depth--;
	errno = edata->saved_errno;
	if (!errstart(elevel, edata->filename, edata->lineno, edata->funcname))
		return;					/* nothing to do */

	/*
	 * Format error message just like errmsg().
	 */
	recursion_depth++;
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	EVALUATE_MESSAGE(message, false);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;

	/*
	 * And let errfinish() finish up.
	 */
	errfinish(0);
}

/*
 * Actual output of the top-of-stack error message
 *
 * In the ereport(ERROR) case this is called from PostgresMain (or not at all,
 * if the error is caught by somebody).  For all other severity levels this
 * is called by errfinish.
 */
void
EmitErrorReport(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	MemoryContext oldcontext;

	recursion_depth++;
	CHECK_STACK_DEPTH();
	oldcontext = MemoryContextSwitchTo(ErrorContext);

	/* Send to server log, if enabled */
	if (edata->output_to_server)
		send_message_to_server_log(edata);

	/* Send to client, if enabled */
	if (edata->output_to_client)
		send_message_to_frontend(edata);

	MemoryContextSwitchTo(oldcontext);
	recursion_depth--;
}

/*
 * CopyErrorData --- obtain a copy of the topmost error stack entry
 *
 * This is only for use in error handler code.  The data is copied into the
 * current memory context, so callers should always switch away from
 * ErrorContext first; otherwise it will be lost when FlushErrorState is done.
 */
ErrorData *
CopyErrorData(void)
{
	ErrorData  *edata = &errordata[errordata_stack_depth];
	ErrorData  *newedata;

	/*
	 * we don't increment recursion_depth because out-of-memory here does
	 * not indicate a problem within the error subsystem.
	 */
	CHECK_STACK_DEPTH();

	Assert(CurrentMemoryContext != ErrorContext);

	/* Copy the struct itself */
	newedata = (ErrorData *) palloc(sizeof(ErrorData));
	memcpy(newedata, edata, sizeof(ErrorData));

	/* Make copies of separately-allocated fields */
	if (newedata->message)
		newedata->message = pstrdup(newedata->message);
	if (newedata->detail)
		newedata->detail = pstrdup(newedata->detail);
	if (newedata->hint)
		newedata->hint = pstrdup(newedata->hint);
	if (newedata->context)
		newedata->context = pstrdup(newedata->context);
	if (newedata->internalquery)
		newedata->internalquery = pstrdup(newedata->internalquery);

	return newedata;
}

/*
 * FreeErrorData --- free the structure returned by CopyErrorData.
 *
 * Error handlers should use this in preference to assuming they know all
 * the separately-allocated fields.
 */
void
FreeErrorData(ErrorData *edata)
{
	if (edata->message)
		pfree(edata->message);
	if (edata->detail)
		pfree(edata->detail);
	if (edata->hint)
		pfree(edata->hint);
	if (edata->context)
		pfree(edata->context);
	if (edata->internalquery)
		pfree(edata->internalquery);
	pfree(edata);
}

/*
 * FlushErrorState --- flush the error state after error recovery
 *