debugger_on_self.patch

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index dca5efc..04cd900 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -5049,3 +5049,34 @@ InitPostmasterDeathWatchHandle(void)
 								 (int) GetLastError())));
 #endif   /* WIN32 */
 }
+
+/* Fork a gdb process such that it emits my stack trace to the logs */
+static void
+print_self_stack()
+{
+	char pid_buf[30];
+	int child_pid;
+
+	sprintf(pid_buf, "%d", getpid());
+	child_pid = fork();
+
+	if (child_pid == 0)
+	{
+		fprintf(stderr, "stack trace for %s pid=%s\n", my_exec_path, pid_buf);
+		execlp("gdb", "gdb", "--batch", "-n", "-ex", "bt", my_exec_path, pid_buf, NULL);
+		abort(); /* If gdb failed to start */
+	}
+	else
+	{
+		waitpid(child_pid,NULL,0);
+	}
+}
+
+/* SIGSEGV handler, controlled by GUC */
+void
+dump_stack(SIGNAL_ARGS)
+{
+	print_self_stack();
+
+	abort();
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 5841631..7262839 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -40,6 +40,7 @@
 #include "libpq/auth.h"
 #include "libpq/be-fsstubs.h"
 #include "libpq/pqformat.h"
+#include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "optimizer/cost.h"
 #include "optimizer/geqo.h"
@@ -167,6 +168,10 @@ static bool call_enum_check_hook(struct config_enum * conf, int *newval,
 static bool check_log_destination(char **newval, void **extra, GucSource source);
 static void assign_log_destination(const char *newval, void *extra);
 
+bool		dump_stack_on_crash = false;
+static bool check_dump_stack_on_crash(bool *newval, void **extra, GucSource source);
+static void assign_dump_stack_on_crash(bool newval, void *extra);
+
 #ifdef HAVE_SYSLOG
 static int	syslog_facility = LOG_LOCAL0;
 #else
@@ -1422,6 +1427,17 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"dump_stack_on_crash", PGC_USERSET, ERROR_HANDLING_OPTIONS,
+			gettext_noop("Use GDB to dump the stack of a crashing backend process."),
+			gettext_noop("This requires that GDB be already installed and accessible to Postgres."),
+		},
+		&quote_all_identifiers,
+		false,
+		check_dump_stack_on_crash, assign_dump_stack_on_crash, NULL
+	},
+
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL
@@ -8672,4 +8688,35 @@ show_log_file_mode(void)
 	return buf;
 }
 
+static bool
+check_dump_stack_on_crash(bool *newval, void **extra, GucSource source)
+{
+	/* TODO: Check if GDB is available. If not, then complain and return false */
+
+	char gdb_path[MAXPGPATH];
+
+	if (*newval == false)
+		return true;
+
+	Assert(*newval == true);
+
+	if (find_my_exec("gdb", gdb_path) < 0)
+	{
+		elog(WARNING, "Could not locate gdb.");
+
+		return false;
+	}
+	else
+		return true;
+}
+
+static void
+assign_dump_stack_on_crash(const bool newval, void *extra)
+{
+	if (newval)
+		pqsignal(SIGSEGV, dump_stack);
+	else
+		pqsignal(SIGSEGV, SIG_DFL);
+}
+
 #include "guc-file.c"
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index be4f8a7..f624d51 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -55,6 +55,8 @@ extern int	SubPostmasterMain(int argc, char *argv[]);
 
 extern Size ShmemBackendArraySize(void);
 extern void ShmemBackendArrayAllocation(void);
+extern void dump_stack(SIGNAL_ARGS);
+
 #endif
 
 #endif   /* _POSTMASTER_H */