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e3a87b4991cc2d00b7a3082abb54c5f12baedfd1
postgres/src/include/utils/elog.h
Tom Lane e3a87b4991 Re-implement the ereport() macro using __VA_ARGS__. 
Now that we require C99, we can depend on __VA_ARGS__ to work, and
revising ereport() to use it has several significant benefits:

* The extra parentheses around the auxiliary function calls are now
optional.  Aside from being a bit less ugly, this removes a common
gotcha for new contributors, because in some cases the compiler errors
you got from forgetting them were unintelligible.

* The auxiliary function calls are now evaluated as a comma expression
list rather than as extra arguments to errfinish().  This means that
compilers can be expected to warn about no-op expressions in the list,
allowing detection of several other common mistakes such as forgetting
to add errmsg(...) when converting an elog() call to ereport().

* Unlike the situation with extra function arguments, comma expressions
are guaranteed to be evaluated left-to-right, so this removes platform
dependency in the order of the auxiliary function calls.  While that
dependency hasn't caused us big problems in the past, this change does
allow dropping some rather shaky assumptions around errcontext() domain
handling.

There's no intention to make wholesale changes of existing ereport
calls, but as proof-of-concept this patch removes the extra parens
from a couple of calls in postgres.c.

While new code can be written either way, code intended to be
back-patched will need to use extra parens for awhile yet.  It seems
worth back-patching this change into v12, so as to reduce the window
where we have to be careful about that by one year.  Hence, this patch
is careful to preserve ABI compatibility; a followup HEAD-only patch
will make some additional simplifications.

Andres Freund and Tom Lane

Discussion: https://postgr.es/m/CA+fd4k6N8EjNvZpM8nme+y+05mz-SM8Z_BgkixzkA34R+ej0Kw@mail.gmail.com
2020-03-24 11:49:00 -04:00

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/*-------------------------------------------------------------------------
*
* elog.h
* POSTGRES error reporting/logging definitions.
*
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/elog.h
*
*-------------------------------------------------------------------------
*/
#ifndef ELOG_H
#define ELOG_H
#include <setjmp.h>
/* Error level codes */
#define DEBUG5 10 /* Debugging messages, in categories of
* decreasing detail. */
#define DEBUG4 11
#define DEBUG3 12
#define DEBUG2 13
#define DEBUG1 14 /* used by GUC debug_* variables */
#define LOG 15 /* Server operational messages; sent only to
* server log by default. */
#define LOG_SERVER_ONLY 16 /* Same as LOG for server reporting, but never
* sent to client. */
#define COMMERROR LOG_SERVER_ONLY /* Client communication problems; same as
* LOG for server reporting, but never
* sent to client. */
#define INFO 17 /* Messages specifically requested by user (eg
* VACUUM VERBOSE output); always sent to
* client regardless of client_min_messages,
* but by default not sent to server log. */
#define NOTICE 18 /* Helpful messages to users about query
* operation; sent to client and not to server
* log by default. */
#define WARNING 19 /* Warnings. NOTICE is for expected messages
* like implicit sequence creation by SERIAL.
* WARNING is for unexpected messages. */
#define ERROR 20 /* user error - abort transaction; return to
* known state */
/* Save ERROR value in PGERROR so it can be restored when Win32 includes
* modify it. We have to use a constant rather than ERROR because macros
* are expanded only when referenced outside macros.
*/
#ifdef WIN32
#define PGERROR 20
#endif
#define FATAL 21 /* fatal error - abort process */
#define PANIC 22 /* take down the other backends with me */
/* #define DEBUG DEBUG1 */ /* Backward compatibility with pre-7.3 */
/* macros for representing SQLSTATE strings compactly */
#define PGSIXBIT(ch) (((ch) - '0') & 0x3F)
#define PGUNSIXBIT(val) (((val) & 0x3F) + '0')
#define MAKE_SQLSTATE(ch1,ch2,ch3,ch4,ch5) \
(PGSIXBIT(ch1) + (PGSIXBIT(ch2) << 6) + (PGSIXBIT(ch3) << 12) + \
(PGSIXBIT(ch4) << 18) + (PGSIXBIT(ch5) << 24))
/* These macros depend on the fact that '0' becomes a zero in PGSIXBIT */
#define ERRCODE_TO_CATEGORY(ec) ((ec) & ((1 << 12) - 1))
#define ERRCODE_IS_CATEGORY(ec) (((ec) & ~((1 << 12) - 1)) == 0)
/* SQLSTATE codes for errors are defined in a separate file */
#include "utils/errcodes.h"
/*
* Provide a way to prevent "errno" from being accidentally used inside an
* elog() or ereport() invocation. Since we know that some operating systems
* define errno as something involving a function call, we'll put a local
* variable of the same name as that function in the local scope to force a
* compile error. On platforms that don't define errno in that way, nothing
* happens, so we get no warning ... but we can live with that as long as it
* happens on some popular platforms.
*/
#if defined(errno) && defined(__linux__)
#define pg_prevent_errno_in_scope() int __errno_location pg_attribute_unused()
#elif defined(errno) && (defined(__darwin__) || defined(__freebsd__))
#define pg_prevent_errno_in_scope() int __error pg_attribute_unused()
#else
#define pg_prevent_errno_in_scope()
#endif
/*----------
* New-style error reporting API: to be used in this way:
* ereport(ERROR,
* errcode(ERRCODE_UNDEFINED_CURSOR),
* errmsg("portal \"%s\" not found", stmt->portalname),
* ... other errxxx() fields as needed ...);
*
* The error level is required, and so is a primary error message (errmsg
* or errmsg_internal). All else is optional. errcode() defaults to
* ERRCODE_INTERNAL_ERROR if elevel is ERROR or more, ERRCODE_WARNING
* if elevel is WARNING, or ERRCODE_SUCCESSFUL_COMPLETION if elevel is
* NOTICE or below.
*
* Before Postgres v12, extra parentheses were required around the
* list of auxiliary function calls; that's now optional.
*
* ereport_domain() allows a message domain to be specified, for modules that
* wish to use a different message catalog from the backend's. To avoid having
* one copy of the default text domain per .o file, we define it as NULL here
* and have errstart insert the default text domain. Modules can either use
* ereport_domain() directly, or preferably they can override the TEXTDOMAIN
* macro.
*
* If elevel >= ERROR, the call will not return; we try to inform the compiler
* of that via pg_unreachable(). However, no useful optimization effect is
* obtained unless the compiler sees elevel as a compile-time constant, else
* we're just adding code bloat. So, if __builtin_constant_p is available,
* use that to cause the second if() to vanish completely for non-constant
* cases. We avoid using a local variable because it's not necessary and
* prevents gcc from making the unreachability deduction at optlevel -O0.
*----------
*/
#ifdef HAVE__BUILTIN_CONSTANT_P
#define ereport_domain(elevel, domain, ...) \
do { \
pg_prevent_errno_in_scope(); \
if (errstart(elevel, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
__VA_ARGS__, errfinish(0); \
if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
pg_unreachable(); \
} while(0)
#else /* !HAVE__BUILTIN_CONSTANT_P */
#define ereport_domain(elevel, domain, ...) \
do { \
const int elevel_ = (elevel); \
pg_prevent_errno_in_scope(); \
if (errstart(elevel_, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
__VA_ARGS__, errfinish(0); \
if (elevel_ >= ERROR) \
pg_unreachable(); \
} while(0)
#endif /* HAVE__BUILTIN_CONSTANT_P */
#define ereport(elevel, ...) \
ereport_domain(elevel, TEXTDOMAIN, __VA_ARGS__)
#define TEXTDOMAIN NULL
extern bool errstart(int elevel, const char *filename, int lineno,
const char *funcname, const char *domain);
extern void errfinish(int dummy,...);
extern int errcode(int sqlerrcode);
extern int errcode_for_file_access(void);
extern int errcode_for_socket_access(void);
extern int errmsg(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errmsg_internal(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errmsg_plural(const char *fmt_singular, const char *fmt_plural,
unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
extern int errdetail(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errdetail_internal(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errdetail_log(const char *fmt,...) pg_attribute_printf(1, 2);
extern int errdetail_log_plural(const char *fmt_singular,
const char *fmt_plural,
unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
extern int errdetail_plural(const char *fmt_singular, const char *fmt_plural,
unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
extern int errhint(const char *fmt,...) pg_attribute_printf(1, 2);
/*
* errcontext() is typically called in error context callback functions, not
* within an ereport() invocation. The callback function can be in a different
* module than the ereport() call, so the message domain passed in errstart()
* is not usually the correct domain for translating the context message.
* set_errcontext_domain() first sets the domain to be used, and
* errcontext_msg() passes the actual message.
*/
#define errcontext set_errcontext_domain(TEXTDOMAIN), errcontext_msg
extern int set_errcontext_domain(const char *domain);
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);
extern int internalerrposition(int cursorpos);
extern int internalerrquery(const char *query);
extern int err_generic_string(int field, const char *str);
extern int geterrcode(void);
extern int geterrposition(void);
extern int getinternalerrposition(void);
/*----------
* Old-style error reporting API: to be used in this way:
* elog(ERROR, "portal \"%s\" not found", stmt->portalname);
*----------
*/
/*
* Using variadic macros, we can give the compiler a hint about the
* call not returning when elevel >= ERROR. See comments for ereport().
* Note that historically elog() has called elog_start (which saves errno)
* before evaluating "elevel", so we preserve that behavior here.
*/
#ifdef HAVE__BUILTIN_CONSTANT_P
#define elog(elevel, ...) \
do { \
pg_prevent_errno_in_scope(); \
elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
elog_finish(elevel, __VA_ARGS__); \
if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
pg_unreachable(); \
} while(0)
#else /* !HAVE__BUILTIN_CONSTANT_P */
#define elog(elevel, ...) \
do { \
pg_prevent_errno_in_scope(); \
elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
{ \
const int elevel_ = (elevel); \
elog_finish(elevel_, __VA_ARGS__); \
if (elevel_ >= ERROR) \
pg_unreachable(); \
} \
} while(0)
#endif /* HAVE__BUILTIN_CONSTANT_P */
extern void elog_start(const char *filename, int lineno, const char *funcname);
extern void elog_finish(int elevel, const char *fmt,...) pg_attribute_printf(2, 3);
/* Support for constructing error strings separately from ereport() calls */
extern void pre_format_elog_string(int errnumber, const char *domain);
extern char *format_elog_string(const char *fmt,...) pg_attribute_printf(1, 2);
/* Support for attaching context information to error reports */
typedef struct ErrorContextCallback
{
struct ErrorContextCallback *previous;
void (*callback) (void *arg);
void *arg;
} ErrorContextCallback;
extern PGDLLIMPORT ErrorContextCallback *error_context_stack;
/*----------
* API for catching ereport(ERROR) exits. Use these macros like so:
*
* PG_TRY();
* {
* ... code that might throw ereport(ERROR) ...
* }
* PG_CATCH();
* {
* ... error recovery code ...
* }
* PG_END_TRY();
*
* (The braces are not actually necessary, but are recommended so that
* pgindent will indent the construct nicely.) The error recovery code
* can either do PG_RE_THROW to propagate the error outwards, or do a
* (sub)transaction abort. Failure to do so may leave the system in an
* inconsistent state for further processing.
*
* For the common case that the error recovery code and the cleanup in the
* normal code path are identical, the following can be used instead:
*
* PG_TRY();
* {
* ... code that might throw ereport(ERROR) ...
* }
* PG_FINALLY();
* {
* ... cleanup code ...
* }
* PG_END_TRY();
*
* The cleanup code will be run in either case, and any error will be rethrown
* afterwards.
*
* You cannot use both PG_CATCH() and PG_FINALLY() in the same
* PG_TRY()/PG_END_TRY() block.
*
* Note: while the system will correctly propagate any new ereport(ERROR)
* occurring in the recovery section, there is a small limit on the number
* of levels this will work for. It's best to keep the error recovery
* section simple enough that it can't generate any new errors, at least
* not before popping the error stack.
*
* Note: an ereport(FATAL) will not be caught by this construct; control will
* exit straight through proc_exit(). Therefore, do NOT put any cleanup
* of non-process-local resources into the error recovery section, at least
* not without taking thought for what will happen during ereport(FATAL).
* The PG_ENSURE_ERROR_CLEANUP macros provided by storage/ipc.h may be
* helpful in such cases.
*
* Note: if a local variable of the function containing PG_TRY is modified
* in the PG_TRY section and used in the PG_CATCH section, that variable
* must be declared "volatile" for POSIX compliance. This is not mere
* pedantry; we have seen bugs from compilers improperly optimizing code
* away when such a variable was not marked. Beware that gcc's -Wclobbered
* warnings are just about entirely useless for catching such oversights.
*----------
*/
#define PG_TRY() \
do { \
sigjmp_buf *_save_exception_stack = PG_exception_stack; \
ErrorContextCallback *_save_context_stack = error_context_stack; \
sigjmp_buf _local_sigjmp_buf; \
bool _do_rethrow = false; \
if (sigsetjmp(_local_sigjmp_buf, 0) == 0) \
{ \
PG_exception_stack = &_local_sigjmp_buf
#define PG_CATCH() \
} \
else \
{ \
PG_exception_stack = _save_exception_stack; \
error_context_stack = _save_context_stack
#define PG_FINALLY() \
} \
else \
_do_rethrow = true; \
{ \
PG_exception_stack = _save_exception_stack; \
error_context_stack = _save_context_stack
#define PG_END_TRY() \
} \
if (_do_rethrow) \
PG_RE_THROW(); \
PG_exception_stack = _save_exception_stack; \
error_context_stack = _save_context_stack; \
} while (0)
/*
* Some compilers understand pg_attribute_noreturn(); for other compilers,
* insert pg_unreachable() so that the compiler gets the point.
*/
#ifdef HAVE_PG_ATTRIBUTE_NORETURN
#define PG_RE_THROW() \
pg_re_throw()
#else
#define PG_RE_THROW() \
(pg_re_throw(), pg_unreachable())
#endif
extern PGDLLIMPORT sigjmp_buf *PG_exception_stack;
/* Stuff that error handlers might want to use */
/*
* ErrorData holds the data accumulated during any one ereport() cycle.
* Any non-NULL pointers must point to palloc'd data.
* (The const pointers are an exception; we assume they point at non-freeable
* constant strings.)
*/
typedef struct ErrorData
{
int elevel; /* error level */
bool output_to_server; /* will report to server log? */
bool output_to_client; /* will report to client? */
bool show_funcname; /* true to force funcname inclusion */
bool hide_stmt; /* true to prevent STATEMENT: inclusion */
bool hide_ctx; /* true to prevent CONTEXT: inclusion */
const char *filename; /* __FILE__ of ereport() call */
int lineno; /* __LINE__ of ereport() call */
const char *funcname; /* __func__ of ereport() call */
const char *domain; /* message domain */
const char *context_domain; /* message domain for context message */
int sqlerrcode; /* encoded ERRSTATE */
char *message; /* primary error message (translated) */
char *detail; /* detail error message */
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 */
char *column_name; /* name of column */
char *datatype_name; /* name of datatype */
char *constraint_name; /* name of constraint */
int cursorpos; /* cursor index into query string */
int internalpos; /* cursor index into internalquery */
char *internalquery; /* text of internally-generated query */
int saved_errno; /* errno at entry */
/* context containing associated non-constant strings */
struct MemoryContextData *assoc_context;
} ErrorData;
extern void EmitErrorReport(void);
extern ErrorData *CopyErrorData(void);
extern void FreeErrorData(ErrorData *edata);
extern void FlushErrorState(void);
extern void ReThrowError(ErrorData *edata) pg_attribute_noreturn();
extern void ThrowErrorData(ErrorData *edata);
extern void pg_re_throw(void) pg_attribute_noreturn();
extern char *GetErrorContextStack(void);
/* Hook for intercepting messages before they are sent to the server log */
typedef void (*emit_log_hook_type) (ErrorData *edata);
extern PGDLLIMPORT emit_log_hook_type emit_log_hook;
/* GUC-configurable parameters */
typedef enum
{
PGERROR_TERSE, /* single-line error messages */
PGERROR_DEFAULT, /* recommended style */
PGERROR_VERBOSE /* all the facts, ma'am */
} PGErrorVerbosity;
extern int Log_error_verbosity;
extern char *Log_line_prefix;
extern int Log_destination;
extern char *Log_destination_string;
extern bool syslog_sequence_numbers;
extern bool syslog_split_messages;
/* Log destination bitmap */
#define LOG_DESTINATION_STDERR 1
#define LOG_DESTINATION_SYSLOG 2
#define LOG_DESTINATION_EVENTLOG 4
#define LOG_DESTINATION_CSVLOG 8
/* Other exported functions */
extern void DebugFileOpen(void);
extern char *unpack_sql_state(int sql_state);
extern bool in_error_recursion_trouble(void);
#ifdef HAVE_SYSLOG
extern void set_syslog_parameters(const char *ident, int facility);
#endif
/*
* Write errors to stderr (or by equal means when stderr is
* not available). Used before ereport/elog can be used
* safely (memory context, GUC load etc)
*/
extern void write_stderr(const char *fmt,...) pg_attribute_printf(1, 2);
#endif /* ELOG_H */
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