Subject: [PATCH] errbacktrace

From: Alvaro Herrera <[email-masked]>
Date: Tue, 10 Apr 2018 18:30:29 -0300

---
 src/backend/utils/error/elog.c      | 59 +++++++++++++++++++++++++++++++++++++
 src/include/postgres_ext.h          |  1 +
 src/include/utils/elog.h            |  3 ++
 src/interfaces/libpq/fe-protocol3.c |  3 ++
 4 files changed, 66 insertions(+)

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 16531f7a0f..e531d0009e 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -62,6 +62,7 @@
 #ifdef HAVE_SYSLOG
 #include <syslog.h>
 #endif
+#include <execinfo.h>
 
 #include "access/transam.h"
 #include "access/xact.h"
@@ -493,6 +494,8 @@ errfinish(int dummy,...)
 		pfree(edata->hint);
 	if (edata->context)
 		pfree(edata->context);
+	if (edata->backtrace)
+		pfree(edata->backtrace);
 	if (edata->schema_name)
 		pfree(edata->schema_name);
 	if (edata->table_name)
@@ -811,6 +814,41 @@ errmsg(const char *fmt,...)
 	return 0;					/* return value does not matter */
 }
 
+#define BACKTRACE_FRAMES 100
+int
+errbacktrace(void)
+{
+	ErrorData   *edata = &errordata[errordata_stack_depth];
+	MemoryContext oldcontext;
+	void	   *buf[BACKTRACE_FRAMES];
+	int			nframes;
+	char	  **strfrms;
+	StringInfoData errtrace;
+	int			i;
+
+	recursion_depth++;
+	CHECK_STACK_DEPTH();
+	oldcontext = MemoryContextSwitchTo(edata->assoc_context);
+
+	nframes = backtrace(buf, BACKTRACE_FRAMES);
+	strfrms = backtrace_symbols(buf, nframes);
+	if (strfrms == NULL)
+		return 0;
+
+	initStringInfo(&errtrace);
+
+	/* the first frame is always errbacktrace itself, so skip it */
+	for (i = 1; i < nframes; i++)
+		appendStringInfo(&errtrace, "%s\n", strfrms[i]);
+	free(strfrms);
+
+	edata->backtrace = errtrace.data;
+
+	MemoryContextSwitchTo(oldcontext);
+	recursion_depth--;
+
+	return 0;
+}
 
 /*
  * errmsg_internal --- add a primary error message text to the current error
@@ -1522,6 +1560,8 @@ CopyErrorData(void)
 		newedata->hint = pstrdup(newedata->hint);
 	if (newedata->context)
 		newedata->context = pstrdup(newedata->context);
+	if (newedata->backtrace)
+		newedata->backtrace = pstrdup(newedata->backtrace);
 	if (newedata->schema_name)
 		newedata->schema_name = pstrdup(newedata->schema_name);
 	if (newedata->table_name)
@@ -1560,6 +1600,8 @@ FreeErrorData(ErrorData *edata)
 		pfree(edata->hint);
 	if (edata->context)
 		pfree(edata->context);
+	if (edata->backtrace)
+		pfree(edata->backtrace);
 	if (edata->schema_name)
 		pfree(edata->schema_name);
 	if (edata->table_name)
@@ -1635,6 +1677,8 @@ ThrowErrorData(ErrorData *edata)
 		newedata->hint = pstrdup(edata->hint);
 	if (edata->context)
 		newedata->context = pstrdup(edata->context);
+	if (edata->backtrace)
+		newedata->backtrace = pstrdup(newedata->backtrace);
 	/* assume message_id is not available */
 	if (edata->schema_name)
 		newedata->schema_name = pstrdup(edata->schema_name);
@@ -1702,6 +1746,8 @@ ReThrowError(ErrorData *edata)
 		newedata->hint = pstrdup(newedata->hint);
 	if (newedata->context)
 		newedata->context = pstrdup(newedata->context);
+	if (newedata->backtrace)
+		newedata->backtrace = pstrdup(newedata->backtrace);
 	if (newedata->schema_name)
 		newedata->schema_name = pstrdup(newedata->schema_name);
 	if (newedata->table_name)
@@ -2932,6 +2978,13 @@ send_message_to_server_log(ErrorData *edata)
 			append_with_tabs(&buf, edata->context);
 			appendStringInfoChar(&buf, '\n');
 		}
+		if (edata->backtrace)
+		{
+			log_line_prefix(&buf, edata);
+			appendStringInfoString(&buf, _("BACKTRACE:  "));
+			append_with_tabs(&buf, edata->backtrace);
+			appendStringInfoChar(&buf, '\n');
+		}
 		if (Log_error_verbosity >= PGERROR_VERBOSE)
 		{
 			/* assume no newlines in funcname or filename... */
@@ -3209,6 +3262,12 @@ send_message_to_frontend(ErrorData *edata)
 			err_sendstring(&msgbuf, edata->context);
 		}
 
+		if (edata->backtrace)
+		{
+			pq_sendbyte(&msgbuf, PG_DIAG_BACKTRACE);
+			err_sendstring(&msgbuf, edata->backtrace);
+		}
+
 		if (edata->schema_name)
 		{
 			pq_sendbyte(&msgbuf, PG_DIAG_SCHEMA_NAME);
diff --git a/src/include/postgres_ext.h b/src/include/postgres_ext.h
index fdb61b7cf5..799f0009f0 100644
--- a/src/include/postgres_ext.h
+++ b/src/include/postgres_ext.h
@@ -62,6 +62,7 @@ typedef PG_INT64_TYPE pg_int64;
 #define PG_DIAG_INTERNAL_POSITION 'p'
 #define PG_DIAG_INTERNAL_QUERY	'q'
 #define PG_DIAG_CONTEXT			'W'
+#define PG_DIAG_BACKTRACE		'B'
 #define PG_DIAG_SCHEMA_NAME		's'
 #define PG_DIAG_TABLE_NAME		't'
 #define PG_DIAG_COLUMN_NAME		'c'
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 7a9ba7f2ff..a4343794b0 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -170,6 +170,8 @@ extern int	errcontext_msg(const char *fmt,...) pg_attribute_printf(1, 2);
 extern int	errhidestmt(bool hide_stmt);
 extern int	errhidecontext(bool hide_ctx);
 
+extern int	errbacktrace(void);
+
 extern int	errfunction(const char *funcname);
 extern int	errposition(int cursorpos);
 
@@ -345,6 +347,7 @@ typedef struct ErrorData
 	char	   *detail_log;		/* detail error message for server log only */
 	char	   *hint;			/* hint message */
 	char	   *context;		/* context message */
+	char	   *backtrace;		/* backtrace */
 	const char *message_id;		/* primary message's id (original string) */
 	char	   *schema_name;	/* name of schema */
 	char	   *table_name;		/* name of table */
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index d3ca5d25f6..3d9e40a09c 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -1079,6 +1079,9 @@ pqBuildErrorMessage3(PQExpBuffer msg, const PGresult *res,
 				appendPQExpBuffer(msg, libpq_gettext("CONTEXT:  %s\n"),
 								  val);
 		}
+		val = PQresultErrorField(res, PG_DIAG_BACKTRACE);
+		if (val)
+			appendPQExpBuffer(msg, libpq_gettext("BACKTRACE:  %s\n"), val);
 	}
 	if (verbosity == PQERRORS_VERBOSE)
 	{
-- 
2.11.0

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