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Add backtrace support for error reporting
Add some support for automatically showing backtraces in certain error situations in the server. Backtraces are shown on assertion failure; also, a new setting backtrace_functions can be set to a list of C function names, and all ereport()s and elog()s from the mentioned functions will have backtraces generated. Finally, the function errbacktrace() can be manually added to an ereport() call to generate a backtrace for that call. Authors: Peter Eisentraut, Álvaro Herrera Discussion: https://postgr.es/m//5f48cb47-bf1e-05b6-7aae-3bf2cd01586d@2ndquadrant.com Discussion: https://postgr.es/m/CAMsr+YGL+yfWE=JvbUbnpWtrRZNey7hJ07+zT4bYJdVp4Szdrg@mail.gmail.com
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9 files changed

+315
-2
lines changed

9 files changed

+315
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lines changed

‎configure

+59-2
Original file line numberDiff line numberDiff line change
@@ -11607,6 +11607,63 @@ if test "$ac_res" != no; then :
1160711607

1160811608
fi
1160911609

11610+
# *BSD:
11611+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing backtrace_symbols" >&5
11612+
$as_echo_n "checking for library containing backtrace_symbols... " >&6; }
11613+
if ${ac_cv_search_backtrace_symbols+:} false; then :
11614+
$as_echo_n "(cached) " >&6
11615+
else
11616+
ac_func_search_save_LIBS=$LIBS
11617+
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
11618+
/* end confdefs.h. */
11619+
11620+
/* Override any GCC internal prototype to avoid an error.
11621+
Use char because int might match the return type of a GCC
11622+
builtin and then its argument prototype would still apply. */
11623+
#ifdef __cplusplus
11624+
extern "C"
11625+
#endif
11626+
char backtrace_symbols ();
11627+
int
11628+
main ()
11629+
{
11630+
return backtrace_symbols ();
11631+
;
11632+
return 0;
11633+
}
11634+
_ACEOF
11635+
for ac_lib in '' execinfo; do
11636+
if test -z "$ac_lib"; then
11637+
ac_res="none required"
11638+
else
11639+
ac_res=-l$ac_lib
11640+
LIBS="-l$ac_lib $ac_func_search_save_LIBS"
11641+
fi
11642+
if ac_fn_c_try_link "$LINENO"; then :
11643+
ac_cv_search_backtrace_symbols=$ac_res
11644+
fi
11645+
rm -f core conftest.err conftest.$ac_objext \
11646+
conftest$ac_exeext
11647+
if ${ac_cv_search_backtrace_symbols+:} false; then :
11648+
break
11649+
fi
11650+
done
11651+
if ${ac_cv_search_backtrace_symbols+:} false; then :
11652+
11653+
else
11654+
ac_cv_search_backtrace_symbols=no
11655+
fi
11656+
rm conftest.$ac_ext
11657+
LIBS=$ac_func_search_save_LIBS
11658+
fi
11659+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_backtrace_symbols" >&5
11660+
$as_echo "$ac_cv_search_backtrace_symbols" >&6; }
11661+
ac_res=$ac_cv_search_backtrace_symbols
11662+
if test "$ac_res" != no; then :
11663+
test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
11664+
11665+
fi
11666+
1161011667

1161111668
if test "$with_readline" = yes; then
1161211669

@@ -12705,7 +12762,7 @@ $as_echo "#define HAVE_STDBOOL_H 1" >>confdefs.h
1270512762
fi
1270612763

1270712764

12708-
for ac_header in atomic.h copyfile.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h
12765+
for ac_header in atomic.h copyfile.h execinfo.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h
1270912766
do :
1271012767
as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
1271112768
ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
@@ -14935,7 +14992,7 @@ fi
1493514992
LIBS_including_readline="$LIBS"
1493614993
LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
1493714994

14938-
for ac_func in cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memset_s memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l
14995+
for ac_func in backtrace_symbols cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memset_s memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l
1493914996
do :
1494014997
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
1494114998
ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"

‎configure.in

+4
Original file line numberDiff line numberDiff line change
@@ -1133,6 +1133,8 @@ AC_SEARCH_LIBS(sched_yield, rt)
11331133
AC_SEARCH_LIBS(gethostbyname_r, nsl)
11341134
# Cygwin:
11351135
AC_SEARCH_LIBS(shmget, cygipc)
1136+
# *BSD:
1137+
AC_SEARCH_LIBS(backtrace_symbols, execinfo)
11361138

11371139
if test "$with_readline" = yes; then
11381140
PGAC_CHECK_READLINE
@@ -1275,6 +1277,7 @@ AC_HEADER_STDBOOL
12751277
AC_CHECK_HEADERS(m4_normalize([
12761278
atomic.h
12771279
copyfile.h
1280+
execinfo.h
12781281
fp_class.h
12791282
getopt.h
12801283
ieeefp.h
@@ -1608,6 +1611,7 @@ LIBS_including_readline="$LIBS"
16081611
LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
16091612

16101613
AC_CHECK_FUNCS(m4_normalize([
1614+
backtrace_symbols
16111615
cbrt
16121616
clock_gettime
16131617
copyfile

‎doc/src/sgml/config.sgml

+26
Original file line numberDiff line numberDiff line change
@@ -9489,6 +9489,32 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
94899489
</listitem>
94909490
</varlistentry>
94919491

9492+
<varlistentry id="guc-backtrace-functions" xreflabel="backtrace_functions">
9493+
<term><varname>backtrace_functions</varname> (<type>string</type>)
9494+
<indexterm>
9495+
<primary><varname>backtrace_functions</varname> configuration parameter</primary>
9496+
</indexterm>
9497+
</term>
9498+
<listitem>
9499+
<para>
9500+
This parameter contains a comma-separated list of C function names.
9501+
If an error is raised and the name of the internal C function where
9502+
the error happens matches a value in the list, then a backtrace is
9503+
written to the server log together with the error message. This can
9504+
be used to debug specific areas of the source code.
9505+
</para>
9506+
9507+
<para>
9508+
Backtrace support is not available on all platforms, and the quality
9509+
of the backtraces depends on compilation options.
9510+
</para>
9511+
9512+
<para>
9513+
This parameter can only be set by superusers.
9514+
</para>
9515+
</listitem>
9516+
</varlistentry>
9517+
94929518
<varlistentry id="guc-ignore-system-indexes" xreflabel="ignore_system_indexes">
94939519
<term><varname>ignore_system_indexes</varname> (<type>boolean</type>)
94949520
<indexterm>

‎src/backend/utils/error/assert.c

+13
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,9 @@
1818
#include "postgres.h"
1919

2020
#include <unistd.h>
21+
#ifdef HAVE_EXECINFO_H
22+
#include <execinfo.h>
23+
#endif
2124

2225
/*
2326
* ExceptionalCondition - Handles the failure of an Assert()
@@ -42,6 +45,16 @@ ExceptionalCondition(const char *conditionName,
4245
/* Usually this shouldn't be needed, but make sure the msg went out */
4346
fflush(stderr);
4447

48+
#ifdef HAVE_BACKTRACE_SYMBOLS
49+
{
50+
void *buf[100];
51+
int nframes;
52+
53+
nframes = backtrace(buf, lengthof(buf));
54+
backtrace_symbols_fd(buf, nframes, fileno(stderr));
55+
}
56+
#endif
57+
4558
#ifdef SLEEP_ON_ASSERT
4659

4760
/*

‎src/backend/utils/error/elog.c

+117
Original file line numberDiff line numberDiff line change
@@ -62,6 +62,9 @@
6262
#ifdef HAVE_SYSLOG
6363
#include <syslog.h>
6464
#endif
65+
#ifdef HAVE_EXECINFO_H
66+
#include <execinfo.h>
67+
#endif
6568

6669
#include "access/transam.h"
6770
#include "access/xact.h"
@@ -167,6 +170,7 @@ static char formatted_log_time[FORMATTED_TS_LEN];
167170

168171

169172
static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
173+
static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
170174
static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
171175
static void write_console(const char *line, int len);
172176
static void setup_formatted_log_time(void);
@@ -398,6 +402,32 @@ errstart(int elevel, const char *filename, int lineno,
398402
return true;
399403
}
400404

405+
/*
406+
* Checks whether the given funcname matches backtrace_functions; see
407+
* check_backtrace_functions.
408+
*/
409+
static bool
410+
matches_backtrace_functions(const char *funcname)
411+
{
412+
char *p;
413+
414+
if (!backtrace_symbol_list || funcname == NULL || funcname[0] == '\0')
415+
return false;
416+
417+
p = backtrace_symbol_list;
418+
for (;;)
419+
{
420+
if (*p == '\0') /* end of backtrace_symbol_list */
421+
break;
422+
423+
if (strcmp(funcname, p) == 0)
424+
return true;
425+
p += strlen(p) + 1;
426+
}
427+
428+
return false;
429+
}
430+
401431
/*
402432
* errfinish --- end an error-reporting cycle
403433
*
@@ -424,6 +454,12 @@ errfinish(int dummy,...)
424454
*/
425455
oldcontext = MemoryContextSwitchTo(ErrorContext);
426456

457+
if (!edata->backtrace &&
458+
edata->funcname &&
459+
backtrace_functions &&
460+
matches_backtrace_functions(edata->funcname))
461+
set_backtrace(edata, 2);
462+
427463
/*
428464
* Call any context callback functions. Errors occurring in callback
429465
* functions will be treated as recursive errors --- this ensures we will
@@ -488,6 +524,8 @@ errfinish(int dummy,...)
488524
pfree(edata->hint);
489525
if (edata->context)
490526
pfree(edata->context);
527+
if (edata->backtrace)
528+
pfree(edata->backtrace);
491529
if (edata->schema_name)
492530
pfree(edata->schema_name);
493531
if (edata->table_name)
@@ -798,6 +836,65 @@ errmsg(const char *fmt,...)
798836
return 0; /* return value does not matter */
799837
}
800838

839+
/*
840+
* Add a backtrace to the containing ereport() call. This is intended to be
841+
* added temporarily during debugging.
842+
*/
843+
int
844+
errbacktrace(void)
845+
{
846+
ErrorData *edata = &errordata[errordata_stack_depth];
847+
MemoryContext oldcontext;
848+
849+
Assert(false);
850+
851+
recursion_depth++;
852+
CHECK_STACK_DEPTH();
853+
oldcontext = MemoryContextSwitchTo(edata->assoc_context);
854+
855+
set_backtrace(edata, 1);
856+
857+
MemoryContextSwitchTo(oldcontext);
858+
recursion_depth--;
859+
860+
return 0;
861+
}
862+
863+
/*
864+
* Compute backtrace data and add it to the supplied ErrorData. num_skip
865+
* specifies how many inner frames to skip. Use this to avoid showing the
866+
* internal backtrace support functions in the backtrace. This requires that
867+
* this and related functions are not inlined.
868+
*/
869+
static void
870+
set_backtrace(ErrorData *edata, int num_skip)
871+
{
872+
StringInfoData errtrace;
873+
874+
initStringInfo(&errtrace);
875+
876+
#ifdef HAVE_BACKTRACE_SYMBOLS
877+
{
878+
void *buf[100];
879+
int nframes;
880+
char **strfrms;
881+
882+
nframes = backtrace(buf, lengthof(buf));
883+
strfrms = backtrace_symbols(buf, nframes);
884+
if (strfrms == NULL)
885+
return;
886+
887+
for (int i = num_skip; i < nframes; i++)
888+
appendStringInfo(&errtrace, "\n%s", strfrms[i]);
889+
free(strfrms);
890+
}
891+
#else
892+
appendStringInfoString(&errtrace,
893+
"backtrace generation is not supported by this installation");
894+
#endif
895+
896+
edata->backtrace = errtrace.data;
897+
}
801898

802899
/*
803900
* errmsg_internal --- add a primary error message text to the current error
@@ -1353,6 +1450,11 @@ elog_finish(int elevel, const char *fmt,...)
13531450
recursion_depth++;
13541451
oldcontext = MemoryContextSwitchTo(edata->assoc_context);
13551452

1453+
if (!edata->backtrace &&
1454+
edata->funcname &&
1455+
matches_backtrace_functions(edata->funcname))
1456+
set_backtrace(edata, 2);
1457+
13561458
edata->message_id = fmt;
13571459
EVALUATE_MESSAGE(edata->domain, message, false, false);
13581460

@@ -1509,6 +1611,8 @@ CopyErrorData(void)
15091611
newedata->hint = pstrdup(newedata->hint);
15101612
if (newedata->context)
15111613
newedata->context = pstrdup(newedata->context);
1614+
if (newedata->backtrace)
1615+
newedata->backtrace = pstrdup(newedata->backtrace);
15121616
if (newedata->schema_name)
15131617
newedata->schema_name = pstrdup(newedata->schema_name);
15141618
if (newedata->table_name)
@@ -1547,6 +1651,8 @@ FreeErrorData(ErrorData *edata)
15471651
pfree(edata->hint);
15481652
if (edata->context)
15491653
pfree(edata->context);
1654+
if (edata->backtrace)
1655+
pfree(edata->backtrace);
15501656
if (edata->schema_name)
15511657
pfree(edata->schema_name);
15521658
if (edata->table_name)
@@ -1622,6 +1728,8 @@ ThrowErrorData(ErrorData *edata)
16221728
newedata->hint = pstrdup(edata->hint);
16231729
if (edata->context)
16241730
newedata->context = pstrdup(edata->context);
1731+
if (edata->backtrace)
1732+
newedata->backtrace = pstrdup(edata->backtrace);
16251733
/* assume message_id is not available */
16261734
if (edata->schema_name)
16271735
newedata->schema_name = pstrdup(edata->schema_name);
@@ -1689,6 +1797,8 @@ ReThrowError(ErrorData *edata)
16891797
newedata->hint = pstrdup(newedata->hint);
16901798
if (newedata->context)
16911799
newedata->context = pstrdup(newedata->context);
1800+
if (newedata->backtrace)
1801+
newedata->backtrace = pstrdup(newedata->backtrace);
16921802
if (newedata->schema_name)
16931803
newedata->schema_name = pstrdup(newedata->schema_name);
16941804
if (newedata->table_name)
@@ -2914,6 +3024,13 @@ send_message_to_server_log(ErrorData *edata)
29143024
append_with_tabs(&buf, edata->context);
29153025
appendStringInfoChar(&buf, '\n');
29163026
}
3027+
if (edata->backtrace)
3028+
{
3029+
log_line_prefix(&buf, edata);
3030+
appendStringInfoString(&buf, _("BACKTRACE: "));
3031+
append_with_tabs(&buf, edata->backtrace);
3032+
appendStringInfoChar(&buf, '\n');
3033+
}
29173034
if (Log_error_verbosity >= PGERROR_VERBOSE)
29183035
{
29193036
/* assume no newlines in funcname or filename... */

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