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Commite0d4123

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committed
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 parentaf2d484 commite0d4123

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7 files changed

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-2
lines changed

7 files changed

+88
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lines changed

‎config/c-compiler.m4

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -396,6 +396,28 @@ fi])# PGAC_CHECK_BUILTIN_FUNC
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# PGAC_CHECK_BUILTIN_FUNC_PTR
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# -----------------------
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# Like PGAC_CHECK_BUILTIN_FUNC, except that the function is assumed to
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# return a pointer type, and the argument(s) should be given literally.
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# This handles some cases that PGAC_CHECK_BUILTIN_FUNC doesn't.
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AC_DEFUN([PGAC_CHECK_BUILTIN_FUNC_PTR],
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[AC_CACHE_CHECK(for$1,pgac_cv$1,
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[AC_LINK_IFELSE([AC_LANG_PROGRAM([
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void *
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call$1(void)
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{
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return$1($2);
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}],[])],
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[pgac_cv$1=yes],
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[pgac_cv$1=no])])
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if test x"${pgac_cv$1}" = xyes ; then
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AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE$1]),1,
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[Define to 1 if your compiler understands$1.])
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fi])# PGAC_CHECK_BUILTIN_FUNC_PTR
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# PGAC_PROG_VARCC_VARFLAGS_OPT
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# -----------------------
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# Given a compiler, variable name and a string, check if the compiler

‎configure

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Original file line numberDiff line numberDiff line change
@@ -15763,6 +15763,46 @@ cat >>confdefs.h <<_ACEOF
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#define HAVE__BUILTIN_POPCOUNT 1
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_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.
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{ $as_echo "$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.$ac_ext
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/* end confdefs.h. */
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void *
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call__builtin_frame_address(void)
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{
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return __builtin_frame_address(0);
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}
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int
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main ()
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{
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;
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return 0;
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}
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_ACEOF
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if ac_fn_c_try_link "$LINENO"; then :
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pgac_cv__builtin_frame_address=yes
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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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fi
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ac_fn_c_check_func "$LINENO" "fseeko" "ac_cv_func_fseeko"

‎configure.in

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Original file line numberDiff line numberDiff line change
@@ -1724,6 +1724,9 @@ 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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AC_REPLACE_FUNCS(fseeko)
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case $host_os in

‎src/backend/postmaster/postmaster.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1207,7 +1207,7 @@ PostmasterMain(int argc, char *argv[])
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/*
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* Set reference point for stack-depth checking.
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*/
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set_stack_base();
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(void)set_stack_base();
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/*
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* Initialize pipe (or process handle on Windows) that allows children to

‎src/backend/tcop/postgres.c

Lines changed: 11 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3210,7 +3210,9 @@ ia64_get_bsp(void)
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pg_stack_base_t
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set_stack_base(void)
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{
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#ifndefHAVE__BUILTIN_FRAME_ADDRESS
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charstack_base;
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#endif
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pg_stack_base_told;
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#if defined(__ia64__)|| defined(__ia64)
@@ -3220,8 +3222,16 @@ set_stack_base(void)
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old=stack_base_ptr;
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#endif
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/* Set up reference point for stack depth checking */
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/*
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* Set up reference point for stack depth checking. On recent gcc we use
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* __builtin_frame_address() to avoid a warning about storing a local
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* variable's address in a long-lived variable.
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*/
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#ifdefHAVE__BUILTIN_FRAME_ADDRESS
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stack_base_ptr=__builtin_frame_address(0);
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#else
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stack_base_ptr=&stack_base;
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#endif
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#if defined(__ia64__)|| defined(__ia64)
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register_stack_base_ptr=ia64_get_bsp();
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#endif

‎src/backend/utils/init/miscinit.c

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -274,6 +274,14 @@ InitPostmasterChild(void)
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{
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IsUnderPostmaster= true;/* we are a postmaster subprocess now */
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/*
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* Set reference point for stack-depth checking. This might seem
279+
* redundant in !EXEC_BACKEND builds; but it's not because the postmaster
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* launches its children from signal handlers, so we might be running on
281+
* an alternative stack.
282+
*/
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(void)set_stack_base();
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InitProcessGlobals();
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279287
/*

‎src/include/pg_config.h.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -757,6 +757,9 @@
757757
/* Define to 1 if your compiler understands __builtin_ctz. */
758758
#undef HAVE__BUILTIN_CTZ
759759

760+
/* Define to 1 if your compiler understands __builtin_frame_address. */
761+
#undef HAVE__BUILTIN_FRAME_ADDRESS
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760763
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
761764
#undef HAVE__BUILTIN_OP_OVERFLOW
762765

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