On 2019-07-22 20:19, Peter Eisentraut wrote: > On 2019-07-09 11:43, Peter Eisentraut wrote: >> After further research I'm thinking about dropping the libunwind >> support. The backtrace()/backtrace_symbols() API is more widely >> available: darwin, freebsd, linux, netbsd, openbsd (via port), solaris, >> and of course it's built-in, whereas libunwind is only available for >> linux, freebsd, hpux, solaris, and requires an external dependency. > > Here is an updated patch without the libunwind support, some minor > cleanups, documentation, and automatic back traces from assertion failures.
Another updated version. I have changed the configuration setting to backtrace_functions plural, so that you can debug more than one location at once. I had originally wanted to do that but using existing functions like SplitIdentifierString() resulted in lots of complications with error handling (inside error handling!). So here I just hand-coded the list splitting. Seems simple enough. I think this patch is now good to go from my perspective. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From f9d440ec41f49464661960c580c29ce0558a1642 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut <pe...@eisentraut.org> Date: Tue, 13 Aug 2019 01:47:22 +0200 Subject: [PATCH v4] Add backtrace support Add some support for automatically showing backtraces in certain error situations in the server. Backtraces are shown on assertion failure. A new setting backtrace_functions can be set to a list of C function names, and all ereport()s and elog()s from the functions will have backtraces generated. Finally, the function errbacktrace() can be manually added to an ereport() call to generate a backtrace for that call. Discussion: https://www.postgresql.org/message-id/flat/5f48cb47-bf1e-05b6-7aae-3bf2cd015...@2ndquadrant.com --- configure | 61 +++++++++++++++- configure.in | 4 ++ doc/src/sgml/config.sgml | 26 +++++++ src/backend/utils/error/assert.c | 13 ++++ src/backend/utils/error/elog.c | 115 +++++++++++++++++++++++++++++++ src/backend/utils/misc/guc.c | 12 ++++ src/include/pg_config.h.in | 6 ++ src/include/utils/elog.h | 3 + src/include/utils/guc.h | 1 + 9 files changed, 239 insertions(+), 2 deletions(-) diff --git a/configure b/configure index 7a6bfc2339..fbd8224f50 100755 --- a/configure +++ b/configure @@ -11662,6 +11662,63 @@ if test "$ac_res" != no; then : fi +# *BSD: +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing backtrace_symbols" >&5 +$as_echo_n "checking for library containing backtrace_symbols... " >&6; } +if ${ac_cv_search_backtrace_symbols+:} false; then : + $as_echo_n "(cached) " >&6 +else + ac_func_search_save_LIBS=$LIBS +cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + +/* Override any GCC internal prototype to avoid an error. + Use char because int might match the return type of a GCC + builtin and then its argument prototype would still apply. */ +#ifdef __cplusplus +extern "C" +#endif +char backtrace_symbols (); +int +main () +{ +return backtrace_symbols (); + ; + return 0; +} +_ACEOF +for ac_lib in '' execinfo; do + if test -z "$ac_lib"; then + ac_res="none required" + else + ac_res=-l$ac_lib + LIBS="-l$ac_lib $ac_func_search_save_LIBS" + fi + if ac_fn_c_try_link "$LINENO"; then : + ac_cv_search_backtrace_symbols=$ac_res +fi +rm -f core conftest.err conftest.$ac_objext \ + conftest$ac_exeext + if ${ac_cv_search_backtrace_symbols+:} false; then : + break +fi +done +if ${ac_cv_search_backtrace_symbols+:} false; then : + +else + ac_cv_search_backtrace_symbols=no +fi +rm conftest.$ac_ext +LIBS=$ac_func_search_save_LIBS +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_backtrace_symbols" >&5 +$as_echo "$ac_cv_search_backtrace_symbols" >&6; } +ac_res=$ac_cv_search_backtrace_symbols +if test "$ac_res" != no; then : + test "$ac_res" = "none required" || LIBS="$ac_res $LIBS" + +fi + if test "$with_readline" = yes; then @@ -12760,7 +12817,7 @@ $as_echo "#define HAVE_STDBOOL_H 1" >>confdefs.h fi -for ac_header in atomic.h copyfile.h crypt.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h +for ac_header in atomic.h copyfile.h crypt.h execinfo.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.h do : as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh` ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default" @@ -15143,7 +15200,7 @@ fi LIBS_including_readline="$LIBS" LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'` -for ac_func in cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l +for ac_func in backtrace_symbols cbrt clock_gettime copyfile fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll posix_fallocate ppoll pstat pthread_is_threaded_np readlink setproctitle setproctitle_fast setsid shm_open strchrnul strsignal symlink sync_file_range uselocale utime utimes wcstombs_l do : as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh` ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var" diff --git a/configure.in b/configure.in index dde3eec89f..f0c5ec9f47 100644 --- a/configure.in +++ b/configure.in @@ -1131,6 +1131,8 @@ AC_SEARCH_LIBS(sched_yield, rt) AC_SEARCH_LIBS(gethostbyname_r, nsl) # Cygwin: AC_SEARCH_LIBS(shmget, cygipc) +# *BSD: +AC_SEARCH_LIBS(backtrace_symbols, execinfo) if test "$with_readline" = yes; then PGAC_CHECK_READLINE @@ -1274,6 +1276,7 @@ AC_CHECK_HEADERS(m4_normalize([ atomic.h copyfile.h crypt.h + execinfo.h fp_class.h getopt.h ieeefp.h @@ -1588,6 +1591,7 @@ LIBS_including_readline="$LIBS" LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'` AC_CHECK_FUNCS(m4_normalize([ + backtrace_symbols cbrt clock_gettime copyfile diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index cdc30fa5e3..10e6c80ac1 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -9285,6 +9285,32 @@ <title>Developer Options</title> </listitem> </varlistentry> + <varlistentry id="guc-backtrace-functions" xreflabel="backtrace_functions"> + <term><varname>backtrace_functions</varname> (<type>string</type>) + <indexterm> + <primary><varname>backtrace_functions</varname> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + This parameter contains a comma-separated list of C function names. + If an error is raised and the name of the internal C function where + the error happens matches a value in the list, then a backtrace is + written to the server log together with the error message. This can + be used to debug specific areas of the source code. + </para> + + <para> + Backtrace support is not available on all platforms, and the quality + of the backtraces depends on compilation options. + </para> + + <para> + This parameter can only be set by superusers. + </para> + </listitem> + </varlistentry> + <varlistentry id="guc-ignore-system-indexes" xreflabel="ignore_system_indexes"> <term><varname>ignore_system_indexes</varname> (<type>boolean</type>) <indexterm> diff --git a/src/backend/utils/error/assert.c b/src/backend/utils/error/assert.c index 2050b4355d..14707fc296 100644 --- a/src/backend/utils/error/assert.c +++ b/src/backend/utils/error/assert.c @@ -18,6 +18,9 @@ #include "postgres.h" #include <unistd.h> +#ifdef HAVE_EXECINFO_H +#include <execinfo.h> +#endif /* * ExceptionalCondition - Handles the failure of an Assert() @@ -42,6 +45,16 @@ ExceptionalCondition(const char *conditionName, /* Usually this shouldn't be needed, but make sure the msg went out */ fflush(stderr); +#ifdef HAVE_BACKTRACE_SYMBOLS + { + void *buf[100]; + int nframes; + + nframes = backtrace(buf, sizeof(buf)); + backtrace_symbols_fd(buf, nframes, fileno(stderr)); + } +#endif + #ifdef SLEEP_ON_ASSERT /* diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c index 8b4720ef3a..12a37e4ac5 100644 --- a/src/backend/utils/error/elog.c +++ b/src/backend/utils/error/elog.c @@ -62,6 +62,9 @@ #ifdef HAVE_SYSLOG #include <syslog.h> #endif +#ifdef HAVE_EXECINFO_H +#include <execinfo.h> +#endif #include "access/transam.h" #include "access/xact.h" @@ -166,6 +169,7 @@ static char formatted_log_time[FORMATTED_TS_LEN]; } while (0) +static pg_noinline void set_backtrace(ErrorData *edata, int num_skip); static const char *err_gettext(const char *str) pg_attribute_format_arg(1); static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str); static void write_console(const char *line, int len); @@ -398,6 +402,33 @@ errstart(int elevel, const char *filename, int lineno, return true; } +/* + * Checks whether the given funcname matches the comma-separated list in backtrace_functions. + * + * This is coded separately here instead of using an existing list-splitting + * function so that we can control the error behavior carefully, since this is + * called during error processing. + */ +static bool +matches_backtrace_functions(const char *funcname) +{ + char *setting = strdup(backtrace_functions); + + if (!setting) + return false; + + for (char *token = strtok(setting, ","); token; token = strtok(NULL, ",")) + { + if (strcmp(token, funcname) == 0) + { + free(setting); + return true; + } + } + free(setting); + return false; +} + /* * errfinish --- end an error-reporting cycle * @@ -424,6 +455,12 @@ errfinish(int dummy,...) */ oldcontext = MemoryContextSwitchTo(ErrorContext); + if (!edata->backtrace && + edata->funcname && + backtrace_functions && + matches_backtrace_functions(edata->funcname)) + set_backtrace(edata, 2); + /* * Call any context callback functions. Errors occurring in callback * functions will be treated as recursive errors --- this ensures we will @@ -488,6 +525,8 @@ 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) @@ -798,6 +837,62 @@ errmsg(const char *fmt,...) return 0; /* return value does not matter */ } +/* + * Add a backtrace to the containing ereport() call. This is intended to be + * added temporarily during debugging. + */ +int +errbacktrace(void) +{ + ErrorData *edata = &errordata[errordata_stack_depth]; + MemoryContext oldcontext; + + recursion_depth++; + CHECK_STACK_DEPTH(); + oldcontext = MemoryContextSwitchTo(edata->assoc_context); + + set_backtrace(edata, 1); + + MemoryContextSwitchTo(oldcontext); + recursion_depth--; + + return 0; +} + +/* + * Compute backtrace data and add it to the supplied ErrorData. num_skip + * specifies how many inner frames to skip. Use this to avoid showing the + * internal backtrace support functions in the backtrace. This requires that + * this and related functions are not inlined. + */ +static void +set_backtrace(ErrorData *edata, int num_skip) +{ + StringInfoData errtrace; + + initStringInfo(&errtrace); + +#ifdef HAVE_BACKTRACE_SYMBOLS + { + void *buf[100]; + int nframes; + char **strfrms; + + nframes = backtrace(buf, sizeof(buf)); + strfrms = backtrace_symbols(buf, nframes); + if (strfrms == NULL) + return; + + for (int i = num_skip; i < nframes; i++) + appendStringInfo(&errtrace, "\n%s", strfrms[i]); + free(strfrms); + } +#else + appendStringInfoString(&errtrace, "backtrace not supported"); +#endif + + edata->backtrace = errtrace.data; +} /* * errmsg_internal --- add a primary error message text to the current error @@ -1353,6 +1448,11 @@ elog_finish(int elevel, const char *fmt,...) recursion_depth++; oldcontext = MemoryContextSwitchTo(edata->assoc_context); + if (!edata->backtrace && + edata->funcname && + matches_backtrace_functions(edata->funcname) == 0) + set_backtrace(edata, 2); + edata->message_id = fmt; EVALUATE_MESSAGE(edata->domain, message, false, false); @@ -1509,6 +1609,8 @@ 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) @@ -1547,6 +1649,8 @@ 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) @@ -1622,6 +1726,8 @@ ThrowErrorData(ErrorData *edata) newedata->hint = pstrdup(edata->hint); if (edata->context) newedata->context = pstrdup(edata->context); + if (edata->backtrace) + newedata->backtrace = pstrdup(edata->backtrace); /* assume message_id is not available */ if (edata->schema_name) newedata->schema_name = pstrdup(edata->schema_name); @@ -1689,6 +1795,8 @@ 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) @@ -2914,6 +3022,13 @@ 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... */ diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index eb78522053..2bb05414e1 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -513,6 +513,7 @@ int log_min_duration_statement = -1; int log_temp_files = -1; double log_xact_sample_rate = 0; int trace_recovery_messages = LOG; +char *backtrace_functions; int temp_file_limit = -1; @@ -4199,6 +4200,17 @@ static struct config_string ConfigureNamesString[] = NULL, NULL, NULL }, + { + {"backtrace_functions", PGC_SUSET, DEVELOPER_OPTIONS, + gettext_noop("Log backtrace for errors in these functions."), + NULL, + GUC_NOT_IN_SAMPLE + }, + &backtrace_functions, + "", + NULL, NULL, NULL + }, + /* End-of-list marker */ { {NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in index 512213aa32..21cd01a66c 100644 --- a/src/include/pg_config.h.in +++ b/src/include/pg_config.h.in @@ -96,6 +96,9 @@ /* Define to 1 if you have the <atomic.h> header file. */ #undef HAVE_ATOMIC_H +/* Define to 1 if you have the `backtrace_symbols' function. */ +#undef HAVE_BACKTRACE_SYMBOLS + /* Define to 1 if you have the `BIO_get_data' function. */ #undef HAVE_BIO_GET_DATA @@ -201,6 +204,9 @@ /* Define to 1 if you have the <editline/readline.h> header file. */ #undef HAVE_EDITLINE_READLINE_H +/* Define to 1 if you have the <execinfo.h> header file. */ +#undef HAVE_EXECINFO_H + /* Define to 1 if you have the `fdatasync' function. */ #undef HAVE_FDATASYNC diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h index ba0b7f6f79..6a315414e2 100644 --- a/src/include/utils/elog.h +++ b/src/include/utils/elog.h @@ -189,6 +189,8 @@ 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); @@ -362,6 +364,7 @@ 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/include/utils/guc.h b/src/include/utils/guc.h index 6791e0cbc2..af8d5a6cdd 100644 --- a/src/include/utils/guc.h +++ b/src/include/utils/guc.h @@ -254,6 +254,7 @@ extern PGDLLIMPORT int client_min_messages; extern int log_min_duration_statement; extern int log_temp_files; extern double log_xact_sample_rate; +extern char *backtrace_functions; extern int temp_file_limit; base-commit: 66bde49d96a9ddacc49dcbdf1b47b5bd6e31ead5 -- 2.22.0
