pg_noreturn to replace pg_attribute_noreturn()

We want to support a "noreturn" decoration on more compilers besides
just GCC-compatible ones, but for that we need to move the decoration
in front of the function declaration instead of either behind it or
wherever, which is the current style afforded by GCC-style attributes.
Also rename the macro to "pg_noreturn" to be similar to the C11
standard "noreturn".

pg_noreturn is now supported on all compilers that support C11 (using
_Noreturn), as well as GCC-compatible ones (using __attribute__, as
before), as well as MSVC (using __declspec).  (When PostgreSQL
requires C11, the latter two variants can be dropped.)

Now, all supported compilers effectively support pg_noreturn, so the
extra code for !HAVE_PG_ATTRIBUTE_NORETURN can be dropped.

This also fixes a possible problem if third-party code includes
stdnoreturn.h, because then the current definition of

    #define pg_attribute_noreturn() __attribute__((noreturn))

would cause an error.

Note that the C standard does not support a noreturn attribute on
function pointer types.  So we have to drop these here.  There are
only two instances at this time, so it's not a big loss.  In one case,
we can make up for it by adding the pg_noreturn to a wrapper function
and adding a pg_unreachable(), in the other case, the latter was
already done before.

Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/pxr5b3z7jmkpenssra5zroxi7qzzp6eswuggokw64axmdixpnk@zbwxuq7gbbcw

6 files changed, 16 insertions, 16 deletions

diff --git a/src/bin/pg_combinebackup/load_manifest.c b/src/bin/pg_combinebackup/load_manifest.c
index 485fe518e41..8e0d04a26a6 100644
--- a/src/bin/pg_combinebackup/load_manifest.c
+++ b/src/bin/pg_combinebackup/load_manifest.c
@@ -68,9 +68,9 @@ static void combinebackup_per_wal_range_cb(JsonManifestParseContext *context,
 										   TimeLineID tli,
 										   XLogRecPtr start_lsn,
 										   XLogRecPtr end_lsn);
-static void report_manifest_error(JsonManifestParseContext *context,
-								  const char *fmt,...)
-			pg_attribute_printf(2, 3) pg_attribute_noreturn();
+pg_noreturn static void report_manifest_error(JsonManifestParseContext *context,
+											  const char *fmt,...)
+			pg_attribute_printf(2, 3);
 
 /*
  * Load backup_manifest files from an array of backups and produces an array
diff --git a/src/bin/pg_dump/pg_backup_utils.h b/src/bin/pg_dump/pg_backup_utils.h
index 38551944513..ba042016879 100644
--- a/src/bin/pg_dump/pg_backup_utils.h
+++ b/src/bin/pg_dump/pg_backup_utils.h
@@ -29,7 +29,7 @@ extern const char *progname;
 
 extern void set_dump_section(const char *arg, int *dumpSections);
 extern void on_exit_nicely(on_exit_nicely_callback function, void *arg);
-extern void exit_nicely(int code) pg_attribute_noreturn();
+pg_noreturn extern void exit_nicely(int code);
 
 /* In pg_dump, we modify pg_fatal to call exit_nicely instead of exit */
 #undef pg_fatal
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index f4e375d27c7..4c9d0172149 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -481,7 +481,7 @@ int			get_user_info(char **user_name_p);
 void		check_ok(void);
 void		report_status(eLogType type, const char *fmt,...) pg_attribute_printf(2, 3);
 void		pg_log(eLogType type, const char *fmt,...) pg_attribute_printf(2, 3);
-void		pg_fatal(const char *fmt,...) pg_attribute_printf(1, 2) pg_attribute_noreturn();
+pg_noreturn void pg_fatal(const char *fmt,...) pg_attribute_printf(1, 2);
 void		end_progress_output(void);
 void		cleanup_output_dirs(void);
 void		prep_status(const char *fmt,...) pg_attribute_printf(1, 2);
diff --git a/src/bin/pg_verifybackup/pg_verifybackup.c b/src/bin/pg_verifybackup/pg_verifybackup.c
index 7c720ab98bd..84edd2cdca5 100644
--- a/src/bin/pg_verifybackup/pg_verifybackup.c
+++ b/src/bin/pg_verifybackup/pg_verifybackup.c
@@ -69,9 +69,9 @@ static void verifybackup_per_wal_range_cb(JsonManifestParseContext *context,
 										  TimeLineID tli,
 										  XLogRecPtr start_lsn,
 										  XLogRecPtr end_lsn);
-static void report_manifest_error(JsonManifestParseContext *context,
-								  const char *fmt,...)
-			pg_attribute_printf(2, 3) pg_attribute_noreturn();
+pg_noreturn static void report_manifest_error(JsonManifestParseContext *context,
+											  const char *fmt,...)
+			pg_attribute_printf(2, 3);
 
 static void verify_tar_backup(verifier_context *context, DIR *dir);
 static void verify_plain_backup_directory(verifier_context *context,
diff --git a/src/bin/pg_verifybackup/pg_verifybackup.h b/src/bin/pg_verifybackup/pg_verifybackup.h
index 622c9d82a81..8cb6f9c53ad 100644
--- a/src/bin/pg_verifybackup/pg_verifybackup.h
+++ b/src/bin/pg_verifybackup/pg_verifybackup.h
@@ -98,8 +98,8 @@ typedef struct verifier_context
 extern void report_backup_error(verifier_context *context,
 								const char *pg_restrict fmt,...)
 			pg_attribute_printf(2, 3);
-extern void report_fatal_error(const char *pg_restrict fmt,...)
-			pg_attribute_printf(1, 2) pg_attribute_noreturn();
+pg_noreturn extern void report_fatal_error(const char *pg_restrict fmt,...)
+			pg_attribute_printf(1, 2);
 extern bool should_ignore_relpath(verifier_context *context,
 								  const char *relpath);
 
diff --git a/src/bin/pgbench/pgbench.h b/src/bin/pgbench/pgbench.h
index 0ba216e5f72..e053c9e2eb6 100644
--- a/src/bin/pgbench/pgbench.h
+++ b/src/bin/pgbench/pgbench.h
@@ -140,9 +140,9 @@ struct PgBenchExprList
 
 extern int	expr_yyparse(PgBenchExpr **expr_parse_result_p, yyscan_t yyscanner);
 extern int	expr_yylex(union YYSTYPE *yylval_param, yyscan_t yyscanner);
-extern void expr_yyerror(PgBenchExpr **expr_parse_result_p, yyscan_t yyscanner, const char *message) pg_attribute_noreturn();
-extern void expr_yyerror_more(yyscan_t yyscanner, const char *message,
-							  const char *more) pg_attribute_noreturn();
+pg_noreturn extern void expr_yyerror(PgBenchExpr **expr_parse_result_p, yyscan_t yyscanner, const char *message);
+pg_noreturn extern void expr_yyerror_more(yyscan_t yyscanner, const char *message,
+										  const char *more);
 extern bool expr_lex_one_word(PsqlScanState state, PQExpBuffer word_buf,
 							  int *offset);
 extern yyscan_t expr_scanner_init(PsqlScanState state,
@@ -153,9 +153,9 @@ extern char *expr_scanner_get_substring(PsqlScanState state,
 										int start_offset,
 										bool chomp);
 
-extern void syntax_error(const char *source, int lineno, const char *line,
-						 const char *command, const char *msg,
-						 const char *more, int column) pg_attribute_noreturn();
+pg_noreturn extern void syntax_error(const char *source, int lineno, const char *line,
+									 const char *command, const char *msg,
+									 const char *more, int column);
 
 extern bool strtoint64(const char *str, bool errorOK, int64 *result);
 extern bool strtodouble(const char *str, bool errorOK, double *dv);