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Suppress warning about stack_base_ptr with late-model GCC.

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GCC 12 complains that set_stack_base is storing the address of
a local variable in a long-lived pointer.  This is an entirely
reasonable warning (indeed, it just helped us find a bug);
but that behavior is intentional here.  We can work around it
by using __builtin_frame_address(0) instead of a specific local
variable; that produces an address a dozen or so bytes different,
in my testing, but we don't care about such a small difference.
Maybe someday a compiler lacking that function will start to issue
a similar warning, but we'll worry about that when it happens.

Patch by me, per a suggestion from Andres Freund.  Back-patch to
v12, which is as far back as the patch will go without some pain.
(Recently-established project policy would permit a back-patch as
far as 9.2, but I'm disinclined to expend the work until GCC 12
is much more widespread.)

Discussion: https://postgr.es/m/3773792.1645141467@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2022-02-17 22:45:34 -05:00
parent a9e186da81
commit 2e30d77a19
8 changed files with 86 additions and 8 deletions
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40
configure vendored
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@ -15944,6 +15944,46 @@ cat >>confdefs.h <<_ACEOF
#define HAVE__BUILTIN_POPCOUNT 1
_ACEOF
fi
# __builtin_frame_address may draw a diagnostic for non-constant argument,
# so it needs a different test function.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_frame_address" >&5
$as_echo_n "checking for __builtin_frame_address... " >&6; }
if ${pgac_cv__builtin_frame_address+:} false; then :
$as_echo_n "(cached) " >&6
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
void *
call__builtin_frame_address(void)
{
return __builtin_frame_address(0);
}
int
main ()
{
;
return 0;
}
_ACEOF
if ac_fn_c_try_link "$LINENO"; then :
pgac_cv__builtin_frame_address=yes
else
pgac_cv__builtin_frame_address=no
fi
rm -f core conftest.err conftest.$ac_objext \
conftest$ac_exeext conftest.$ac_ext
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_frame_address" >&5
$as_echo "$pgac_cv__builtin_frame_address" >&6; }
if test x"${pgac_cv__builtin_frame_address}" = xyes ; then
cat >>confdefs.h <<_ACEOF
#define HAVE__BUILTIN_FRAME_ADDRESS 1
_ACEOF
fi
# We require 64-bit fseeko() to be available, but run this check anyway