database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Improve handling of ereport(ERROR) and elog(ERROR).

Browse Source 
In commit 71450d7fd6, we added code to inform
suitably-intelligent compilers that ereport() doesn't return if the elevel
is ERROR or higher.  This patch extends that to elog(), and also fixes a
double-evaluation hazard that the previous commit created in ereport(),
as well as reducing the emitted code size.

The elog() improvement requires the compiler to support __VA_ARGS__, which
should be available in just about anything nowadays since it's required by
C99.  But our minimum language baseline is still C89, so add a configure
test for that.

The previous commit assumed that ereport's elevel could be evaluated twice,
which isn't terribly safe --- there are already counterexamples in xlog.c.
On compilers that have __builtin_constant_p, we can use that to protect the
second test, since there's no possible optimization gain if the compiler
doesn't know the value of elevel.  Otherwise, use a local variable inside
the macros to prevent double evaluation.  The local-variable solution is
inferior because (a) it leads to useless code being emitted when elevel
isn't constant, and (b) it increases the optimization level needed for the
compiler to recognize that subsequent code is unreachable.  But it seems
better than not teaching non-gcc compilers about unreachability at all.

Lastly, if the compiler has __builtin_unreachable(), we can use that
instead of abort(), resulting in a noticeable code savings since no
function call is actually emitted.  However, it seems wise to do this only
in non-assert builds.  In an assert build, continue to use abort(), so that
the behavior will be predictable and debuggable if the "impossible"
happens.

These changes involve making the ereport and elog macros emit do-while
statement blocks not just expressions, which forces small changes in
a few call sites.

Andres Freund, Tom Lane, Heikki Linnakangas
This commit is contained in:
Tom Lane
2013-01-13 18:39:20 -05:00
parent 4ae5ee6c9b
commit b853eb9718
12 changed files with 361 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

178
configure vendored
View File

@ -15659,6 +15659,184 @@ cat >>confdefs.h <<\_ACEOF
#define HAVE__BUILTIN_TYPES_COMPATIBLE_P 1
_ACEOF
fi
{ $as_echo "$as_me:$LINENO: checking for __builtin_constant_p" >&5
$as_echo_n "checking for __builtin_constant_p... " >&6; }
if test "${pgac_cv__builtin_constant_p+set}" = set; then
$as_echo_n "(cached) " >&6
else
cat >conftest.$ac_ext <<_ACEOF
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
static int x; static int y[__builtin_constant_p(x) ? x : 1];
int
main ()
{
;
return 0;
}
_ACEOF
rm -f conftest.$ac_objext
if { (ac_try="$ac_compile"
case "(($ac_try" in
*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
*) ac_try_echo=$ac_try;;
esac
eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
$as_echo "$ac_try_echo") >&5
(eval "$ac_compile") 2>conftest.er1
ac_status=$?
grep -v '^ *+' conftest.er1 >conftest.err
rm -f conftest.er1
cat conftest.err >&5
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); } && {
test -z "$ac_c_werror_flag" ||
test ! -s conftest.err
} && test -s conftest.$ac_objext; then
pgac_cv__builtin_constant_p=yes
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
pgac_cv__builtin_constant_p=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
{ $as_echo "$as_me:$LINENO: result: $pgac_cv__builtin_constant_p" >&5
$as_echo "$pgac_cv__builtin_constant_p" >&6; }
if test x"$pgac_cv__builtin_constant_p" = xyes ; then
cat >>confdefs.h <<\_ACEOF
#define HAVE__BUILTIN_CONSTANT_P 1
_ACEOF
fi
{ $as_echo "$as_me:$LINENO: checking for __builtin_unreachable" >&5
$as_echo_n "checking for __builtin_unreachable... " >&6; }
if test "${pgac_cv__builtin_unreachable+set}" = set; then
$as_echo_n "(cached) " >&6
else
cat >conftest.$ac_ext <<_ACEOF
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
int
main ()
{
__builtin_unreachable();
;
return 0;
}
_ACEOF
rm -f conftest.$ac_objext conftest$ac_exeext
if { (ac_try="$ac_link"
case "(($ac_try" in
*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
*) ac_try_echo=$ac_try;;
esac
eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
$as_echo "$ac_try_echo") >&5
(eval "$ac_link") 2>conftest.er1
ac_status=$?
grep -v '^ *+' conftest.er1 >conftest.err
rm -f conftest.er1
cat conftest.err >&5
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); } && {
test -z "$ac_c_werror_flag" ||
test ! -s conftest.err
} && test -s conftest$ac_exeext && {
test "$cross_compiling" = yes ||
$as_test_x conftest$ac_exeext
}; then
pgac_cv__builtin_unreachable=yes
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
pgac_cv__builtin_unreachable=no
fi
rm -rf conftest.dSYM
rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
conftest$ac_exeext conftest.$ac_ext
fi
{ $as_echo "$as_me:$LINENO: result: $pgac_cv__builtin_unreachable" >&5
$as_echo "$pgac_cv__builtin_unreachable" >&6; }
if test x"$pgac_cv__builtin_unreachable" = xyes ; then
cat >>confdefs.h <<\_ACEOF
#define HAVE__BUILTIN_UNREACHABLE 1
_ACEOF
fi
{ $as_echo "$as_me:$LINENO: checking for __VA_ARGS__" >&5
$as_echo_n "checking for __VA_ARGS__... " >&6; }
if test "${pgac_cv__va_args+set}" = set; then
$as_echo_n "(cached) " >&6
else
cat >conftest.$ac_ext <<_ACEOF
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
#include <stdio.h>
int
main ()
{
#define debug(...) fprintf(stderr, __VA_ARGS__)
debug("%s", "blarg");
;
return 0;
}
_ACEOF
rm -f conftest.$ac_objext
if { (ac_try="$ac_compile"
case "(($ac_try" in
*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
*) ac_try_echo=$ac_try;;
esac
eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
$as_echo "$ac_try_echo") >&5
(eval "$ac_compile") 2>conftest.er1
ac_status=$?
grep -v '^ *+' conftest.er1 >conftest.err
rm -f conftest.er1
cat conftest.err >&5
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); } && {
test -z "$ac_c_werror_flag" ||
test ! -s conftest.err
} && test -s conftest.$ac_objext; then
pgac_cv__va_args=yes
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
pgac_cv__va_args=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
{ $as_echo "$as_me:$LINENO: result: $pgac_cv__va_args" >&5
$as_echo "$pgac_cv__va_args" >&6; }
if test x"$pgac_cv__va_args" = xyes ; then
cat >>confdefs.h <<\_ACEOF
#define HAVE__VA_ARGS 1
_ACEOF
fi
{ $as_echo "$as_me:$LINENO: checking whether struct tm is in sys/time.h or time.h" >&5
$as_echo_n "checking whether struct tm is in sys/time.h or time.h... " >&6; }