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Commitde447bb

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Suppress warning about stack_base_ptr with late-model GCC.
GCC 12 complains that set_stack_base is storing the address ofa local variable in a long-lived pointer. This is an entirelyreasonable warning (indeed, it just helped us find a bug);but that behavior is intentional here. We can work around itby using __builtin_frame_address(0) instead of a specific localvariable; 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 issuea similar warning, but we'll worry about that when it happens.Patch by me, per a suggestion from Andres Freund. Back-patch tov12, which is as far back as the patch will go without some pain.(Recently-established project policy would permit a back-patch asfar as 9.2, but I'm disinclined to expend the work until GCC 12is much more widespread.)Discussion:https://postgr.es/m/3773792.1645141467@sss.pgh.pa.us
1 parentf927a6e commitde447bb

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8 files changed

+89
-13
lines changed

8 files changed

+89
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lines changed

‎config/c-compiler.m4

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -381,6 +381,28 @@ fi])# PGAC_CHECK_BUILTIN_FUNC
381381

382382

383383

384+
# PGAC_CHECK_BUILTIN_FUNC_PTR
385+
# -----------------------
386+
# Like PGAC_CHECK_BUILTIN_FUNC, except that the function is assumed to
387+
# return a pointer type, and the argument(s) should be given literally.
388+
# This handles some cases that PGAC_CHECK_BUILTIN_FUNC doesn't.
389+
AC_DEFUN([PGAC_CHECK_BUILTIN_FUNC_PTR],
390+
[AC_CACHE_CHECK(for$1,pgac_cv$1,
391+
[AC_LINK_IFELSE([AC_LANG_PROGRAM([
392+
void *
393+
call$1(void)
394+
{
395+
return$1($2);
396+
}],[])],
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[pgac_cv$1=yes],
398+
[pgac_cv$1=no])])
399+
if test x"${pgac_cv$1}" = xyes ; then
400+
AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE$1]),1,
401+
[Define to 1 if your compiler understands$1.])
402+
fi])# PGAC_CHECK_BUILTIN_FUNC_PTR
403+
404+
405+
384406
# PGAC_PROG_VARCC_VARFLAGS_OPT
385407
# ----------------------------
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# Given a compiler, variable name and a string, check if the compiler

‎configure

Lines changed: 40 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -15944,6 +15944,46 @@ cat >>confdefs.h <<_ACEOF
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#define HAVE__BUILTIN_POPCOUNT 1
1594515945
_ACEOF
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fi
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# __builtin_frame_address may draw a diagnostic for non-constant argument,
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# so it needs a different test function.
15950+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_frame_address" >&5
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$as_echo_n "checking for __builtin_frame_address... " >&6; }
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if ${pgac_cv__builtin_frame_address+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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15958+
void *
15959+
call__builtin_frame_address(void)
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{
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return __builtin_frame_address(0);
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}
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int
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main ()
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{
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15967+
;
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return 0;
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}
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_ACEOF
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if ac_fn_c_try_link "$LINENO"; then :
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pgac_cv__builtin_frame_address=yes
15973+
else
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pgac_cv__builtin_frame_address=no
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fi
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rm -f core conftest.err conftest.$ac_objext \
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conftest$ac_exeext conftest.$ac_ext
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_frame_address" >&5
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$as_echo "$pgac_cv__builtin_frame_address" >&6; }
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if test x"${pgac_cv__builtin_frame_address}" = xyes ; then
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cat >>confdefs.h <<_ACEOF
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#define HAVE__BUILTIN_FRAME_ADDRESS 1
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_ACEOF
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1594715987
fi
1594815988

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# We require 64-bit fseeko() to be available, but run this check anyway

‎configure.ac

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1776,6 +1776,9 @@ PGAC_CHECK_BUILTIN_FUNC([__builtin_bswap64], [long int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_clz],[unsigned int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz],[unsigned int x])
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PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount],[unsigned int x])
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# __builtin_frame_address may draw a diagnostic for non-constant argument,
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# so it needs a different test function.
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PGAC_CHECK_BUILTIN_FUNC_PTR([__builtin_frame_address],[0])
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# We require 64-bit fseeko() to be available, but run this check anyway
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# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.

‎src/backend/postmaster/postmaster.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1083,7 +1083,7 @@ PostmasterMain(int argc, char *argv[])
10831083
/*
10841084
* Set reference point for stack-depth checking.
10851085
*/
1086-
set_stack_base();
1086+
(void)set_stack_base();
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/*
10891089
* Initialize pipe (or process handle on Windows) that allows children to

‎src/backend/tcop/postgres.c

Lines changed: 14 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -129,17 +129,15 @@ static long max_stack_depth_bytes = 100 * 1024L;
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130130
/*
131131
* Stack base pointer -- initialized by PostmasterMain and inherited by
132-
* subprocesses. This is not static because old versions of PL/Java modify
133-
* it directly. Newer versions use set_stack_base(), but we want to stay
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* binary-compatible for the time being.
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* subprocesses (but see also InitPostmasterChild).
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*/
136-
char*stack_base_ptr=NULL;
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staticchar*stack_base_ptr=NULL;
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/*
139137
* On IA64 we also have to remember the register stack base.
140138
*/
141139
#if defined(__ia64__)|| defined(__ia64)
142-
char*register_stack_base_ptr=NULL;
140+
staticchar*register_stack_base_ptr=NULL;
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#endif
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145143
/*
@@ -3416,7 +3414,9 @@ ia64_get_bsp(void)
34163414
pg_stack_base_t
34173415
set_stack_base(void)
34183416
{
3417+
#ifndefHAVE__BUILTIN_FRAME_ADDRESS
34193418
charstack_base;
3419+
#endif
34203420
pg_stack_base_told;
34213421

34223422
#if defined(__ia64__)|| defined(__ia64)
@@ -3426,8 +3426,16 @@ set_stack_base(void)
34263426
old=stack_base_ptr;
34273427
#endif
34283428

3429-
/* Set up reference point for stack depth checking */
3429+
/*
3430+
* Set up reference point for stack depth checking. On recent gcc we use
3431+
* __builtin_frame_address() to avoid a warning about storing a local
3432+
* variable's address in a long-lived variable.
3433+
*/
3434+
#ifdefHAVE__BUILTIN_FRAME_ADDRESS
3435+
stack_base_ptr=__builtin_frame_address(0);
3436+
#else
34303437
stack_base_ptr=&stack_base;
3438+
#endif
34313439
#if defined(__ia64__)|| defined(__ia64)
34323440
register_stack_base_ptr=ia64_get_bsp();
34333441
#endif

‎src/backend/utils/init/miscinit.c

Lines changed: 5 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -106,13 +106,12 @@ InitPostmasterChild(void)
106106
#endif
107107

108108
/*
109-
* Set reference point for stack-depth checking. We re-do that even in the
110-
* !EXEC_BACKEND case, because there are some edge cases where processes
111-
* are started with an alternative stack (e.g. starting bgworkers when
112-
* running postgres using the rr debugger, as bgworkers are launched from
113-
* signal handlers).
109+
* Set reference point for stack-depth checking. This might seem
110+
* redundant in !EXEC_BACKEND builds; but it's not because the postmaster
111+
* launches its children from signal handlers, so we might be running on
112+
* an alternative stack.
114113
*/
115-
set_stack_base();
114+
(void)set_stack_base();
116115

117116
InitProcessGlobals();
118117

‎src/include/pg_config.h.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -739,6 +739,9 @@
739739
/* Define to 1 if your compiler understands __builtin_ctz. */
740740
#undef HAVE__BUILTIN_CTZ
741741

742+
/* Define to 1 if your compiler understands __builtin_frame_address. */
743+
#undef HAVE__BUILTIN_FRAME_ADDRESS
744+
742745
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
743746
#undef HAVE__BUILTIN_OP_OVERFLOW
744747

‎src/tools/msvc/Solution.pm

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -439,6 +439,7 @@ sub GenerateFiles
439439
HAVE__BUILTIN_CLZ=>undef,
440440
HAVE__BUILTIN_CONSTANT_P=>undef,
441441
HAVE__BUILTIN_CTZ=>undef,
442+
HAVE__BUILTIN_FRAME_ADDRESS=>undef,
442443
HAVE__BUILTIN_OP_OVERFLOW=>undef,
443444
HAVE__BUILTIN_POPCOUNT=>undef,
444445
HAVE__BUILTIN_TYPES_COMPATIBLE_P=>undef,

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